dustvoice Steem Profile | Ecosynthesizer

@dustvoice

steemit.com/@dustvoice

VOTING POWER100.00%

DOWNVOTE POWER100.00%

RESOURCE CREDITS100.00%

REPUTATION PROGRESS90.37%

Net Worth

1.500USD

STEEM

0.001STEEM

SBD

2.962SBD

Effective Power

5.007SP

├── Own SP

1.347SP

└── Incoming DelegationsDeleg

+3.659SP

Detailed Balance

STEEM
balance	0.001STEEM	STEEM
market_balance	0.000STEEM	STEEM
savings_balance	0.000STEEM	STEEM
reward_steem_balance	0.000STEEM	STEEM
STEEM POWER
Own SP	1.347SP	SP
Delegated Out	0.000SP	SP
Delegation In	3.659SP	SP
Effective Power	5.007SP	SP
Reward SP (pending)	0.000SP	SP
SBD
sbd_balance	2.962SBD	SBD
sbd_conversions	0.000SBD	SBD
sbd_market_balance	0.000SBD	SBD
savings_sbd_balance	0.000SBD	SBD
reward_sbd_balance	0.000SBD	SBD

{
  "balance": "0.001 STEEM",
  "savings_balance": "0.000 STEEM",
  "reward_steem_balance": "0.000 STEEM",
  "vesting_shares": "2191.754397 VESTS",
  "delegated_vesting_shares": "0.000000 VESTS",
  "received_vesting_shares": "5951.905409 VESTS",
  "sbd_balance": "2.962 SBD",
  "savings_sbd_balance": "0.000 SBD",
  "reward_sbd_balance": "0.000 SBD",
  "conversions": []
}

Account Info

name	dustvoice
id	558356
rank	730,467
reputation	12601023545
created	2018-01-04T12:06:27
recovery_account	steem
proxy	None
post_count	20
comment_count	0
lifetime_vote_count	0
witnesses_voted_for	0
last_post	2018-01-06T14:03:00
last_root_post	2018-01-06T04:02:15
last_vote_time	2018-01-13T22:02:54
proxied_vsf_votes	0, 0, 0, 0
can_vote	1
voting_power	0
delayed_votes	0
balance	0.001 STEEM
savings_balance	0.000 STEEM
sbd_balance	2.962 SBD
savings_sbd_balance	0.000 SBD
vesting_shares	2191.754397 VESTS
delegated_vesting_shares	0.000000 VESTS
received_vesting_shares	5951.905409 VESTS
reward_vesting_balance	0.000000 VESTS
vesting_balance	0.000 STEEM
vesting_withdraw_rate	0.000000 VESTS
next_vesting_withdrawal	1969-12-31T23:59:59
withdrawn	0
to_withdraw	0
withdraw_routes	0
savings_withdraw_requests	0
last_account_recovery	1970-01-01T00:00:00
reset_account	null
last_owner_update	1970-01-01T00:00:00
last_account_update	2021-02-01T02:10:00
mined	No
sbd_seconds	0
sbd_last_interest_payment	2018-01-13T22:00:54
savings_sbd_last_interest_payment	1970-01-01T00:00:00

{
  "active": {
    "account_auths": [],
    "key_auths": [
      [
        "STM8fVSCYFindrWfyACRBjd3e6LRthpKDG47KPrw6n3Tg2zK3yG21",
        1
      ]
    ],
    "weight_threshold": 1
  },
  "balance": "0.001 STEEM",
  "can_vote": true,
  "comment_count": 0,
  "created": "2018-01-04T12:06:27",
  "curation_rewards": 4,
  "delegated_vesting_shares": "0.000000 VESTS",
  "downvote_manabar": {
    "current_mana": 2035914951,
    "last_update_time": 1779061515
  },
  "guest_bloggers": [],
  "id": 558356,
  "json_metadata": "{\"profile\":{\"profile_image\":\"https://s14.postimg.org/a0f3n4az5/Dust_Voice.png\",\"cover_image\":\"https://pbs.twimg.com/profile_banners/720211137070022656/1475770438/1500x500\",\"name\":\"DustVoice\",\"website\":\"http://dustvoice.de\"}}",
  "last_account_recovery": "1970-01-01T00:00:00",
  "last_account_update": "2021-02-01T02:10:00",
  "last_owner_update": "1970-01-01T00:00:00",
  "last_post": "2018-01-06T14:03:00",
  "last_root_post": "2018-01-06T04:02:15",
  "last_vote_time": "2018-01-13T22:02:54",
  "lifetime_vote_count": 0,
  "market_history": [],
  "memo_key": "STM69fmSxgcza1TYkcSgtWYPvnKvuaWoDBovN7bq7vvyHYCubJ2z4",
  "mined": false,
  "name": "dustvoice",
  "next_vesting_withdrawal": "1969-12-31T23:59:59",
  "other_history": [],
  "owner": {
    "account_auths": [],
    "key_auths": [
      [
        "STM73fjp31DVRWU9tynHwLsQYYFqBfsB76iEdpJSFhSJsVTuKab49",
        1
      ]
    ],
    "weight_threshold": 1
  },
  "pending_claimed_accounts": 0,
  "post_bandwidth": 0,
  "post_count": 20,
  "post_history": [],
  "posting": {
    "account_auths": [
      [
        "dmania.app",
        1
      ]
    ],
    "key_auths": [
      [
        "STM5XZRiDa7pe2QwkytkGamYZ1TtzBgKxDoWeDjVzP1oySuD9gLrK",
        1
      ]
    ],
    "weight_threshold": 1
  },
  "posting_json_metadata": "{\"profile\":{\"profile_image\":\"https://cdn.steemitimages.com/DQmYdjT45r1aPnK4Cigvc5LK6Wjo1SDuhGS8LUb8YfzvwSa/crop_image.jpg\",\"cover_image\":\"https://pbs.twimg.com/profile_banners/720211137070022656/1475770438/1500x500\",\"name\":\"DustVoice\",\"website\":\"https://dustvoice.de\",\"version\":2}}",
  "posting_rewards": 1132,
  "proxied_vsf_votes": [
    0,
    0,
    0,
    0
  ],
  "proxy": "",
  "received_vesting_shares": "5951.905409 VESTS",
  "recovery_account": "steem",
  "reputation": "12601023545",
  "reset_account": "null",
  "reward_sbd_balance": "0.000 SBD",
  "reward_steem_balance": "0.000 STEEM",
  "reward_vesting_balance": "0.000000 VESTS",
  "reward_vesting_steem": "0.000 STEEM",
  "savings_balance": "0.000 STEEM",
  "savings_sbd_balance": "0.000 SBD",
  "savings_sbd_last_interest_payment": "1970-01-01T00:00:00",
  "savings_sbd_seconds": "0",
  "savings_sbd_seconds_last_update": "1970-01-01T00:00:00",
  "savings_withdraw_requests": 0,
  "sbd_balance": "2.962 SBD",
  "sbd_last_interest_payment": "2018-01-13T22:00:54",
  "sbd_seconds": "0",
  "sbd_seconds_last_update": "2018-01-13T22:00:54",
  "tags_usage": [],
  "to_withdraw": 0,
  "transfer_history": [],
  "vesting_balance": "0.000 STEEM",
  "vesting_shares": "2191.754397 VESTS",
  "vesting_withdraw_rate": "0.000000 VESTS",
  "vote_history": [],
  "voting_manabar": {
    "current_mana": "8143659806",
    "last_update_time": 1779061515
  },
  "voting_power": 0,
  "withdraw_routes": 0,
  "withdrawn": 0,
  "witness_votes": [],
  "witnesses_voted_for": 0,
  "rank": 730467
}

Withdraw Routes

Incoming	Outgoing
Empty	Empty

{
  "incoming": [],
  "outgoing": []
}

From Date

To Date

steemdelegated 3.659 SP to @dustvoice

2026/05/17 23:45:15 UTC

106,142,852|e6f53cd

delegatee	dustvoice
delegator	steem
vesting shares	5951.905409 VESTS
Transaction Info	Block #106142852/Trx e6f53cdcad6281a6a5342f553a33f164af944800

View Raw JSON Data

{
  "block": 106142852,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "5951.905409 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2026-05-17T23:45:15",
  "trx_id": "e6f53cdcad6281a6a5342f553a33f164af944800",
  "trx_in_block": 0,
  "virtual_op": 0
}

steemdelegated 1.992 SP to @dustvoice

2026/05/12 01:48:39 UTC

105,973,277|b07295c

delegatee	dustvoice
delegator	steem
vesting shares	3239.695004 VESTS
Transaction Info	Block #105973277/Trx b07295ca5d8895d56be8e8802a08056bfdb91162

View Raw JSON Data

{
  "block": 105973277,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "3239.695004 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2026-05-12T01:48:39",
  "trx_id": "b07295ca5d8895d56be8e8802a08056bfdb91162",
  "trx_in_block": 2,
  "virtual_op": 0
}

steemdelegated 3.667 SP to @dustvoice

2026/04/25 23:06:57 UTC

105,510,517|3fcaf3d

delegatee	dustvoice
delegator	steem
vesting shares	5964.421165 VESTS
Transaction Info	Block #105510517/Trx 3fcaf3de454891f62921b90c13959ffc36f02200

View Raw JSON Data

{
  "block": 105510517,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "5964.421165 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2026-04-25T23:06:57",
  "trx_id": "3fcaf3de454891f62921b90c13959ffc36f02200",
  "trx_in_block": 2,
  "virtual_op": 0
}

steemdelegated 2.017 SP to @dustvoice

2026/01/23 06:26:54 UTC

102,850,187|c6c9381

delegatee	dustvoice
delegator	steem
vesting shares	3281.241823 VESTS
Transaction Info	Block #102850187/Trx c6c938104d6ea8fc3a179e8cda47d31c776ac8c8

View Raw JSON Data

{
  "block": 102850187,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "3281.241823 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2026-01-23T06:26:54",
  "trx_id": "c6c938104d6ea8fc3a179e8cda47d31c776ac8c8",
  "trx_in_block": 0,
  "virtual_op": 0
}

steemdelegated 2.118 SP to @dustvoice

2024/12/17 01:46:27 UTC

91,296,607|4f9884d

delegatee	dustvoice
delegator	steem
vesting shares	3445.461020 VESTS
Transaction Info	Block #91296607/Trx 4f9884de465d692095b67ee5d6c793d468b3688f

View Raw JSON Data

{
  "block": 91296607,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "3445.461020 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2024-12-17T01:46:27",
  "trx_id": "4f9884de465d692095b67ee5d6c793d468b3688f",
  "trx_in_block": 9,
  "virtual_op": 0
}

steemdelegated 2.222 SP to @dustvoice

2023/11/13 17:29:21 UTC

79,850,814|0117fda

delegatee	dustvoice
delegator	steem
vesting shares	3614.594552 VESTS
Transaction Info	Block #79850814/Trx 0117fdaf0a9dc98b98de6de42af5bb262298088c

View Raw JSON Data

{
  "block": 79850814,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "3614.594552 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2023-11-13T17:29:21",
  "trx_id": "0117fdaf0a9dc98b98de6de42af5bb262298088c",
  "trx_in_block": 9,
  "virtual_op": 0
}

steemdelegated 4.028 SP to @dustvoice

2023/09/21 21:14:12 UTC

78,347,117|3679a1e

delegatee	dustvoice
delegator	steem
vesting shares	6551.873338 VESTS
Transaction Info	Block #78347117/Trx 3679a1e8fdccd462ca8077dab0cb68c575386254

View Raw JSON Data

{
  "block": 78347117,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "6551.873338 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2023-09-21T21:14:12",
  "trx_id": "3679a1e8fdccd462ca8077dab0cb68c575386254",
  "trx_in_block": 1,
  "virtual_op": 0
}

steemdelegated 4.164 SP to @dustvoice

2022/11/03 11:06:42 UTC

69,112,556|fadca8e

delegatee	dustvoice
delegator	steem
vesting shares	6773.554776 VESTS
Transaction Info	Block #69112556/Trx fadca8e11a560c68a258d2f3e7b555e3b5d91358

View Raw JSON Data

{
  "block": 69112556,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "6773.554776 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2022-11-03T11:06:42",
  "trx_id": "fadca8e11a560c68a258d2f3e7b555e3b5d91358",
  "trx_in_block": 2,
  "virtual_op": 0
}

steemdelegated 4.300 SP to @dustvoice

2022/01/17 10:25:30 UTC

60,808,779|39df067

delegatee	dustvoice
delegator	steem
vesting shares	6994.088007 VESTS
Transaction Info	Block #60808779/Trx 39df0674bfdceeca8450580a198f28d90dfa57c3

View Raw JSON Data

{
  "block": 60808779,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "6994.088007 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2022-01-17T10:25:30",
  "trx_id": "39df0674bfdceeca8450580a198f28d90dfa57c3",
  "trx_in_block": 17,
  "virtual_op": 0
}

steemdelegated 4.413 SP to @dustvoice

2021/06/14 00:22:03 UTC

54,607,192|6e0f374

delegatee	dustvoice
delegator	steem
vesting shares	7177.856665 VESTS
Transaction Info	Block #54607192/Trx 6e0f374a21b04e0f2226ae962d7be57d83b26682

View Raw JSON Data

{
  "block": 54607192,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "7177.856665 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2021-06-14T00:22:03",
  "trx_id": "6e0f374a21b04e0f2226ae962d7be57d83b26682",
  "trx_in_block": 1,
  "virtual_op": 0
}

dustvoicecustom json: notify

2021/02/01 02:12:51 UTC

50,823,756|fa34491

id	notify
json	["setLastRead",{"date":"2021-02-01T02:12:47"}]
required auths	[]
required posting auths	["dustvoice"]
Transaction Info	Block #50823756/Trx fa34491940b0f3a70fe324bc532092240d686b5b

View Raw JSON Data

{
  "block": 50823756,
  "op": [
    "custom_json",
    {
      "id": "notify",
      "json": "[\"setLastRead\",{\"date\":\"2021-02-01T02:12:47\"}]",
      "required_auths": [],
      "required_posting_auths": [
        "dustvoice"
      ]
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2021-02-01T02:12:51",
  "trx_id": "fa34491940b0f3a70fe324bc532092240d686b5b",
  "trx_in_block": 5,
  "virtual_op": 0
}

dustvoiceupdated their account properties

2021/02/01 02:10:00 UTC

50,823,699|81b49d6

account	dustvoice
extensions	[]
json metadata
posting json metadata	{"profile":{"profile_image":"https://cdn.steemitimages.com/DQmYdjT45r1aPnK4Cigvc5LK6Wjo1SDuhGS8LUb8YfzvwSa/crop_image.jpg","cover_image":"https://pbs.twimg.com/profile_banners/720211137070022656/1475770438/1500x500","name":"DustVoice","website":"https://dustvoice.de","version":2}}
Transaction Info	Block #50823699/Trx 81b49d6c706614abf1f83056c39381205e8a97e0

View Raw JSON Data

{
  "block": 50823699,
  "op": [
    "account_update2",
    {
      "account": "dustvoice",
      "extensions": [],
      "json_metadata": "",
      "posting_json_metadata": "{\"profile\":{\"profile_image\":\"https://cdn.steemitimages.com/DQmYdjT45r1aPnK4Cigvc5LK6Wjo1SDuhGS8LUb8YfzvwSa/crop_image.jpg\",\"cover_image\":\"https://pbs.twimg.com/profile_banners/720211137070022656/1475770438/1500x500\",\"name\":\"DustVoice\",\"website\":\"https://dustvoice.de\",\"version\":2}}"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2021-02-01T02:10:00",
  "trx_id": "81b49d6c706614abf1f83056c39381205e8a97e0",
  "trx_in_block": 5,
  "virtual_op": 0
}

steemdelegated 4.528 SP to @dustvoice

2020/12/11 10:41:54 UTC

49,354,678|19e081b

delegatee	dustvoice
delegator	steem
vesting shares	7365.278639 VESTS
Transaction Info	Block #49354678/Trx 19e081b2eeb081f8520c8ac67aad1b1c6ad19645

View Raw JSON Data

{
  "block": 49354678,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "7365.278639 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2020-12-11T10:41:54",
  "trx_id": "19e081b2eeb081f8520c8ac67aad1b1c6ad19645",
  "trx_in_block": 1,
  "virtual_op": 0
}

steemdelegated 1.176 SP to @dustvoice

2020/12/06 04:19:12 UTC

49,206,243|ff43e61

delegatee	dustvoice
delegator	steem
vesting shares	1912.543513 VESTS
Transaction Info	Block #49206243/Trx ff43e619c63f899cea75c896507968a2b491e144

View Raw JSON Data

{
  "block": 49206243,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "1912.543513 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2020-12-06T04:19:12",
  "trx_id": "ff43e619c63f899cea75c896507968a2b491e144",
  "trx_in_block": 5,
  "virtual_op": 0
}

steemdelegated 4.532 SP to @dustvoice

2020/12/05 14:20:06 UTC

49,189,775|dae8708

delegatee	dustvoice
delegator	steem
vesting shares	7371.486493 VESTS
Transaction Info	Block #49189775/Trx dae8708cffd94888576bfd0defd90ace70301ee2

View Raw JSON Data

{
  "block": 49189775,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "7371.486493 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2020-12-05T14:20:06",
  "trx_id": "dae8708cffd94888576bfd0defd90ace70301ee2",
  "trx_in_block": 6,
  "virtual_op": 0
}

steemdelegated 1.180 SP to @dustvoice

2020/11/02 14:39:42 UTC

48,256,647|5491cee

delegatee	dustvoice
delegator	steem
vesting shares	1920.017158 VESTS
Transaction Info	Block #48256647/Trx 5491cee36dd8af5b316876d6f1fe0ed736fdd0d4

View Raw JSON Data

{
  "block": 48256647,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "1920.017158 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2020-11-02T14:39:42",
  "trx_id": "5491cee36dd8af5b316876d6f1fe0ed736fdd0d4",
  "trx_in_block": 7,
  "virtual_op": 0
}

steemdelegated 4.657 SP to @dustvoice

2020/05/09 05:15:51 UTC

43,216,479|c02f6a6

delegatee	dustvoice
delegator	steem
vesting shares	7574.291852 VESTS
Transaction Info	Block #43216479/Trx c02f6a696c6c9694a0fff9eb30009589cc07847f

View Raw JSON Data

{
  "block": 43216479,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "7574.291852 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2020-05-09T05:15:51",
  "trx_id": "c02f6a696c6c9694a0fff9eb30009589cc07847f",
  "trx_in_block": 1,
  "virtual_op": 0
}

steemdelegated 1.201 SP to @dustvoice

2020/05/08 08:47:36 UTC

43,192,490|60bdaca

delegatee	dustvoice
delegator	steem
vesting shares	1953.311140 VESTS
Transaction Info	Block #43192490/Trx 60bdaca8aef0310b247d4c2242390e662c80ac21

View Raw JSON Data

{
  "block": 43192490,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "1953.311140 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2020-05-08T08:47:36",
  "trx_id": "60bdaca8aef0310b247d4c2242390e662c80ac21",
  "trx_in_block": 6,
  "virtual_op": 0
}

steemdelegated 4.665 SP to @dustvoice

2020/04/15 21:19:27 UTC

42,562,220|caaae21

delegatee	dustvoice
delegator	steem
vesting shares	7587.269271 VESTS
Transaction Info	Block #42562220/Trx caaae21e5874fd5d01f175161f0533c5326fce08

View Raw JSON Data

{
  "block": 42562220,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "7587.269271 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2020-04-15T21:19:27",
  "trx_id": "caaae21e5874fd5d01f175161f0533c5326fce08",
  "trx_in_block": 22,
  "virtual_op": 0
}

steemitboardreplied to @dustvoice / steemitboard-notify-dustvoice-20200104t135136000z

2020/01/04 13:51:36 UTC

39,635,180|9a7b343

author	steemitboard
body	Congratulations @dustvoice! You received a personal award! <table><tr><td>https://steemitimages.com/70x70/http://steemitboard.com/@dustvoice/birthday2.png</td><td>Happy Birthday! - You are on the Steem blockchain for 2 years!</td></tr></table> <sub>_You can view [your badges on your Steem Board](https://steemitboard.com/@dustvoice) and compare to others on the [Steem Ranking](https://steemitboard.com/ranking/index.php?name=dustvoice)_</sub> ###### [Vote for @Steemitboard as a witness](https://v2.steemconnect.com/sign/account-witness-vote?witness=steemitboard&approve=1) to get one more award and increased upvotes!
json metadata	{"image":["https://steemitboard.com/img/notify.png"]}
parent author	dustvoice
parent permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
permlink	steemitboard-notify-dustvoice-20200104t135136000z
title
Transaction Info	Block #39635180/Trx 9a7b3433e3362d5bf603c7a04465fb82fdd48c39

View Raw JSON Data

{
  "block": 39635180,
  "op": [
    "comment",
    {
      "author": "steemitboard",
      "body": "Congratulations @dustvoice! You received a personal award!\n\n<table><tr><td>https://steemitimages.com/70x70/http://steemitboard.com/@dustvoice/birthday2.png</td><td>Happy Birthday! - You are on the Steem blockchain for 2 years!</td></tr></table>\n\n<sub>_You can view [your badges on your Steem Board](https://steemitboard.com/@dustvoice) and compare to others on the [Steem Ranking](https://steemitboard.com/ranking/index.php?name=dustvoice)_</sub>\n\n\n###### [Vote for @Steemitboard as a witness](https://v2.steemconnect.com/sign/account-witness-vote?witness=steemitboard&approve=1) to get one more award and increased upvotes!",
      "json_metadata": "{\"image\":[\"https://steemitboard.com/img/notify.png\"]}",
      "parent_author": "dustvoice",
      "parent_permlink": "create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required",
      "permlink": "steemitboard-notify-dustvoice-20200104t135136000z",
      "title": ""
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2020-01-04T13:51:36",
  "trx_id": "9a7b3433e3362d5bf603c7a04465fb82fdd48c39",
  "trx_in_block": 8,
  "virtual_op": 0
}

dtubesent 0.001 STEEM to @dustvoice- "Time is running out, claim your DTube account now before anyone else can! Login at https://d.tube"

2019/08/22 17:59:30 UTC

35,781,598|c6f6478

amount	0.001 STEEM
from	dtube
memo	Time is running out, claim your DTube account now before anyone else can! Login at https://d.tube
to	dustvoice
Transaction Info	Block #35781598/Trx c6f647834c61455c82daf631a85ad5f590517480

View Raw JSON Data

{
  "block": 35781598,
  "op": [
    "transfer",
    {
      "amount": "0.001 STEEM",
      "from": "dtube",
      "memo": "Time is running out, claim your DTube account now before anyone else can! Login at https://d.tube",
      "to": "dustvoice"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2019-08-22T17:59:30",
  "trx_id": "c6f647834c61455c82daf631a85ad5f590517480",
  "trx_in_block": 11,
  "virtual_op": 0
}

steemdelegated 4.785 SP to @dustvoice

2019/05/12 14:34:18 UTC

32,845,089|874bcdc

delegatee	dustvoice
delegator	steem
vesting shares	7782.892076 VESTS
Transaction Info	Block #32845089/Trx 874bcdc926dd30fab093d87649cf57104f1c10b7

View Raw JSON Data

{
  "block": 32845089,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "7782.892076 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2019-05-12T14:34:18",
  "trx_id": "874bcdc926dd30fab093d87649cf57104f1c10b7",
  "trx_in_block": 6,
  "virtual_op": 0
}

steemitboardreplied to @dustvoice / steemitboard-notify-dustvoice-20190104t135344000z

2019/01/04 13:53:45 UTC

29,162,119|a87ffaf

author	steemitboard
body	Congratulations @dustvoice! You received a personal award! <table><tr><td>https://steemitimages.com/70x70/http://steemitboard.com/@dustvoice/birthday1.png</td><td>1 Year on Steemit</td></tr></table> <sub>_[Click here to view your Board](https://steemitboard.com/@dustvoice)_</sub> > Support [SteemitBoard's project](https://steemit.com/@steemitboard)! [Vote for its witness](https://v2.steemconnect.com/sign/account-witness-vote?witness=steemitboard&approve=1) and get one more award!
json metadata	{"image":["https://steemitboard.com/img/notify.png"]}
parent author	dustvoice
parent permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
permlink	steemitboard-notify-dustvoice-20190104t135344000z
title
Transaction Info	Block #29162119/Trx a87ffaf0266e58521a28820ac7c18a60a37a56ca

View Raw JSON Data

{
  "block": 29162119,
  "op": [
    "comment",
    {
      "author": "steemitboard",
      "body": "Congratulations @dustvoice! You received a personal award!\n\n<table><tr><td>https://steemitimages.com/70x70/http://steemitboard.com/@dustvoice/birthday1.png</td><td>1 Year on Steemit</td></tr></table>\n\n<sub>_[Click here to view your Board](https://steemitboard.com/@dustvoice)_</sub>\n\n\n> Support [SteemitBoard's project](https://steemit.com/@steemitboard)! **[Vote for its witness](https://v2.steemconnect.com/sign/account-witness-vote?witness=steemitboard&approve=1)** and **get one more award**!",
      "json_metadata": "{\"image\":[\"https://steemitboard.com/img/notify.png\"]}",
      "parent_author": "dustvoice",
      "parent_permlink": "create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required",
      "permlink": "steemitboard-notify-dustvoice-20190104t135344000z",
      "title": ""
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  ],
  "op_in_trx": 0,
  "timestamp": "2019-01-04T13:53:45",
  "trx_id": "a87ffaf0266e58521a28820ac7c18a60a37a56ca",
  "trx_in_block": 5,
  "virtual_op": 0
}

steemdelegated 4.907 SP to @dustvoice

2018/05/16 20:15:12 UTC

22,489,805|0519b80

delegatee	dustvoice
delegator	steem
vesting shares	7982.444511 VESTS
Transaction Info	Block #22489805/Trx 0519b80efe28d5b3ba83c5e8497bcbab8f6d4e82

View Raw JSON Data

{
  "block": 22489805,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "7982.444511 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-05-16T20:15:12",
  "trx_id": "0519b80efe28d5b3ba83c5e8497bcbab8f6d4e82",
  "trx_in_block": 16,
  "virtual_op": 0
}

onurguleupvoted (100.00%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/02/17 11:06:30 UTC

19,946,996|e74ed24

author	dustvoice
permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
voter	onurgule
weight	10000 (100.00%)
Transaction Info	Block #19946996/Trx e74ed24ce26bfc7c977e73cd79cd637e8655e660

View Raw JSON Data

{
  "block": 19946996,
  "op": [
    "vote",
    {
      "author": "dustvoice",
      "permlink": "create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required",
      "voter": "onurgule",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-02-17T11:06:30",
  "trx_id": "e74ed24ce26bfc7c977e73cd79cd637e8655e660",
  "trx_in_block": 34,
  "virtual_op": 0
}

steemdelegated 17.538 SP to @dustvoice

2018/01/13 23:45:42 UTC

18,955,189|810fa5d

delegatee	dustvoice
delegator	steem
vesting shares	28526.330483 VESTS
Transaction Info	Block #18955189/Trx 810fa5d2198648ffbc8fa5ce152bb27f5e6f2d6c

View Raw JSON Data

{
  "block": 18955189,
  "op": [
    "delegate_vesting_shares",
    {
      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "28526.330483 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-13T23:45:42",
  "trx_id": "810fa5d2198648ffbc8fa5ce152bb27f5e6f2d6c",
  "trx_in_block": 74,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @resteemator / resteemator-reached-500-followers

2018/01/13 22:02:54 UTC

18,953,133|ed4edcf

author	resteemator
permlink	resteemator-reached-500-followers
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18953133/Trx ed4edcfe0c5b883b2442a051c45611accafd3edc

View Raw JSON Data

{
  "block": 18953133,
  "op": [
    "vote",
    {
      "author": "resteemator",
      "permlink": "resteemator-reached-500-followers",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-13T22:02:54",
  "trx_id": "ed4edcfe0c5b883b2442a051c45611accafd3edc",
  "trx_in_block": 53,
  "virtual_op": 0
}

dustvoicefollowed @resteemator

2018/01/13 22:02:51 UTC

18,953,132|0fce070

id	follow
json	["follow",{"follower":"dustvoice","following":"resteemator","what":["blog"]}]
required auths	[]
required posting auths	["dustvoice"]
Transaction Info	Block #18953132/Trx 0fce0701cb53cb765daee9c053bea79a8aaf5b5b

View Raw JSON Data

{
  "block": 18953132,
  "op": [
    "custom_json",
    {
      "id": "follow",
      "json": "[\"follow\",{\"follower\":\"dustvoice\",\"following\":\"resteemator\",\"what\":[\"blog\"]}]",
      "required_auths": [],
      "required_posting_auths": [
        "dustvoice"
      ]
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-13T22:02:51",
  "trx_id": "0fce0701cb53cb765daee9c053bea79a8aaf5b5b",
  "trx_in_block": 47,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @dustvoice / re-hursh-7hpiuf-free-re-steem-to-all-my-steemit-friends-20180106t140259089z

2018/01/13 22:02:30 UTC

18,953,125|fb2fff2

author	dustvoice
permlink	re-hursh-7hpiuf-free-re-steem-to-all-my-steemit-friends-20180106t140259089z
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18953125/Trx fb2fff2ceded00f53b06c8e3753ff3c258767c94

View Raw JSON Data

{
  "block": 18953125,
  "op": [
    "vote",
    {
      "author": "dustvoice",
      "permlink": "re-hursh-7hpiuf-free-re-steem-to-all-my-steemit-friends-20180106t140259089z",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-13T22:02:30",
  "trx_id": "fb2fff2ceded00f53b06c8e3753ff3c258767c94",
  "trx_in_block": 20,
  "virtual_op": 0
}

dustvoiceclaimed reward balance: 2.886 SBD, 0.696 SP

2018/01/13 22:00:54 UTC

18,953,093|f251ab9

account	dustvoice
reward sbd	2.886 SBD
reward steem	0.000 STEEM
reward vests	1132.522840 VESTS
Transaction Info	Block #18953093/Trx f251ab9f502aee28fef5476460ec88bf8955e500

View Raw JSON Data

{
  "block": 18953093,
  "op": [
    "claim_reward_balance",
    {
      "account": "dustvoice",
      "reward_sbd": "2.886 SBD",
      "reward_steem": "0.000 STEEM",
      "reward_vests": "1132.522840 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-13T22:00:54",
  "trx_id": "f251ab9f502aee28fef5476460ec88bf8955e500",
  "trx_in_block": 41,
  "virtual_op": 0
}

dustvoicereceived 2.886 SBD, 0.696 SP author reward for @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/13 04:02:15 UTC

18,931,552|virtual

author	dustvoice
permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
sbd payout	2.886 SBD
steem payout	0.000 STEEM
vesting payout	1132.522840 VESTS
Transaction Info	Block #18931552/Virtual Operation #41

View Raw JSON Data

{
  "block": 18931552,
  "op": [
    "author_reward",
    {
      "author": "dustvoice",
      "permlink": "create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required",
      "sbd_payout": "2.886 SBD",
      "steem_payout": "0.000 STEEM",
      "vesting_payout": "1132.522840 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-13T04:02:15",
  "trx_id": "0000000000000000000000000000000000000000",
  "trx_in_block": 4294967295,
  "virtual_op": 41
}

dustvoiceclaimed reward balance: 0.076 SBD, 0.021 SP

2018/01/13 00:00:09 UTC

18,926,719|eacee19

account	dustvoice
reward sbd	0.076 SBD
reward steem	0.000 STEEM
reward vests	34.818087 VESTS
Transaction Info	Block #18926719/Trx eacee19de396a66f17af5ba262310a57c10ad536

View Raw JSON Data

{
  "block": 18926719,
  "op": [
    "claim_reward_balance",
    {
      "account": "dustvoice",
      "reward_sbd": "0.076 SBD",
      "reward_steem": "0.000 STEEM",
      "reward_vests": "34.818087 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-13T00:00:09",
  "trx_id": "eacee19de396a66f17af5ba262310a57c10ad536",
  "trx_in_block": 3,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @cephalopod / 45-kb

2018/01/12 23:58:39 UTC

18,926,689|e1d4e04

author	cephalopod
permlink	45-kb
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926689/Trx e1d4e04e7c6e9701cd87ec7262232dd7cece3dc4

View Raw JSON Data

{
  "block": 18926689,
  "op": [
    "vote",
    {
      "author": "cephalopod",
      "permlink": "45-kb",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:58:39",
  "trx_id": "e1d4e04e7c6e9701cd87ec7262232dd7cece3dc4",
  "trx_in_block": 18,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @planet-rium / city-wanders-series-watercolour-made-by-me-planet-rium

2018/01/12 23:58:36 UTC

18,926,688|88e65a4

author	planet-rium
permlink	city-wanders-series-watercolour-made-by-me-planet-rium
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926688/Trx 88e65a42c0b2f5f86768f63737f77d4535e62eb8

View Raw JSON Data

{
  "block": 18926688,
  "op": [
    "vote",
    {
      "author": "planet-rium",
      "permlink": "city-wanders-series-watercolour-made-by-me-planet-rium",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:58:36",
  "trx_id": "88e65a42c0b2f5f86768f63737f77d4535e62eb8",
  "trx_in_block": 26,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @onyemacourage / egghsej5

2018/01/12 23:57:57 UTC

18,926,675|dda7ce9

author	onyemacourage
permlink	egghsej5
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926675/Trx dda7ce91183102744d9f5204fa732a8b8733dbab

View Raw JSON Data

{
  "block": 18926675,
  "op": [
    "vote",
    {
      "author": "onyemacourage",
      "permlink": "egghsej5",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:57:57",
  "trx_id": "dda7ce91183102744d9f5204fa732a8b8733dbab",
  "trx_in_block": 17,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @theaustrianguy / gnejloye

2018/01/12 23:57:51 UTC

18,926,673|992423a

author	theaustrianguy
permlink	gnejloye
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926673/Trx 992423ad31dd0606b32e7f6d5ba39604df6111f7

View Raw JSON Data

{
  "block": 18926673,
  "op": [
    "vote",
    {
      "author": "theaustrianguy",
      "permlink": "gnejloye",
      "voter": "dustvoice",
      "weight": 10000
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  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:57:51",
  "trx_id": "992423ad31dd0606b32e7f6d5ba39604df6111f7",
  "trx_in_block": 5,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @nashbe / steem-and-steem-dollars-midnight-update

2018/01/12 23:57:48 UTC

18,926,672|f387372

author	nashbe
permlink	steem-and-steem-dollars-midnight-update
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926672/Trx f3873725acbb6aba527409bf00b1eee586788727

View Raw JSON Data

{
  "block": 18926672,
  "op": [
    "vote",
    {
      "author": "nashbe",
      "permlink": "steem-and-steem-dollars-midnight-update",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:57:48",
  "trx_id": "f3873725acbb6aba527409bf00b1eee586788727",
  "trx_in_block": 19,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @dhruv120511 / what-will-earth-and-humans-look-like-in-1-000-years

2018/01/12 23:57:45 UTC

18,926,671|4c6a6f8

author	dhruv120511
permlink	what-will-earth-and-humans-look-like-in-1-000-years
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926671/Trx 4c6a6f8d319279e73ee48c8d776f90b14242553c

View Raw JSON Data

{
  "block": 18926671,
  "op": [
    "vote",
    {
      "author": "dhruv120511",
      "permlink": "what-will-earth-and-humans-look-like-in-1-000-years",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:57:45",
  "trx_id": "4c6a6f8d319279e73ee48c8d776f90b14242553c",
  "trx_in_block": 33,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @brandt / one-day-black-and-white-challenge-day-1

2018/01/12 23:57:39 UTC

18,926,669|a2daaa3

author	brandt
permlink	one-day-black-and-white-challenge-day-1
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926669/Trx a2daaa3c277ee2d81189c8db7a99c986573e489d

View Raw JSON Data

{
  "block": 18926669,
  "op": [
    "vote",
    {
      "author": "brandt",
      "permlink": "one-day-black-and-white-challenge-day-1",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:57:39",
  "trx_id": "a2daaa3c277ee2d81189c8db7a99c986573e489d",
  "trx_in_block": 32,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @leohira123 / daily-landscape-shot-the-beautiful-crops-c467d37c5ef5

2018/01/12 23:57:36 UTC

18,926,668|973e901

author	leohira123
permlink	daily-landscape-shot-the-beautiful-crops-c467d37c5ef5
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926668/Trx 973e901ca1a0afb04bb907b6d974de6cc74be5b1

View Raw JSON Data

{
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  "op": [
    "vote",
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      "permlink": "daily-landscape-shot-the-beautiful-crops-c467d37c5ef5",
      "voter": "dustvoice",
      "weight": 10000
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  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:57:36",
  "trx_id": "973e901ca1a0afb04bb907b6d974de6cc74be5b1",
  "trx_in_block": 49,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @ledjo1991 / cryptocurrency-exchanges-need-smarter-faster-and-more-secure-id-verification-with-velix-id

2018/01/12 23:57:33 UTC

18,926,667|53397db

author	ledjo1991
permlink	cryptocurrency-exchanges-need-smarter-faster-and-more-secure-id-verification-with-velix-id
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926667/Trx 53397db0f729eda5f581465891a756d3af574a7d

View Raw JSON Data

{
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      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:57:33",
  "trx_id": "53397db0f729eda5f581465891a756d3af574a7d",
  "trx_in_block": 26,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @evernoticethat / a-thank-you-message-to-my-500-amazing-followers

2018/01/12 23:57:30 UTC

18,926,666|95beb29

author	evernoticethat
permlink	a-thank-you-message-to-my-500-amazing-followers
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18926666/Trx 95beb29eb10bb4129f1f6ea3853da8aa9049db74

View Raw JSON Data

{
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      "voter": "dustvoice",
      "weight": 10000
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  "op_in_trx": 0,
  "timestamp": "2018-01-12T23:57:30",
  "trx_id": "95beb29eb10bb4129f1f6ea3853da8aa9049db74",
  "trx_in_block": 17,
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}

wbjadventuresreplied to @dustvoice / y6u2mff2l

2018/01/12 02:51:30 UTC

18,901,399|c0e05cc

author	wbjadventures
body	Really nice
json metadata	{"app":"dtube/0.6"}
parent author	dustvoice
parent permlink	h8p9o8ul
permlink	y6u2mff2l
title	y6u2mff2l
Transaction Info	Block #18901399/Trx c0e05cc35f6b80bca690ddb00f7ca2adf179547c

View Raw JSON Data

{
  "block": 18901399,
  "op": [
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      "body": "Really nice ",
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      "parent_author": "dustvoice",
      "parent_permlink": "h8p9o8ul",
      "permlink": "y6u2mff2l",
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  "timestamp": "2018-01-12T02:51:30",
  "trx_id": "c0e05cc35f6b80bca690ddb00f7ca2adf179547c",
  "trx_in_block": 5,
  "virtual_op": 0
}

framegamesupvoted (100.00%) @dustvoice / h8p9o8ul

2018/01/11 22:48:21 UTC

18,896,538|e6f0306

author	dustvoice
permlink	h8p9o8ul
voter	framegames
weight	10000 (100.00%)
Transaction Info	Block #18896538/Trx e6f03066eb5be5e074089070ef83bf63209b9639

View Raw JSON Data

{
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      "voter": "framegames",
      "weight": 10000
    }
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  "op_in_trx": 0,
  "timestamp": "2018-01-11T22:48:21",
  "trx_id": "e6f03066eb5be5e074089070ef83bf63209b9639",
  "trx_in_block": 34,
  "virtual_op": 0
}

abdulrehman8833upvoted (100.00%) @dustvoice / h8p9o8ul

2018/01/11 16:10:45 UTC

18,888,587|04812bd

author	dustvoice
permlink	h8p9o8ul
voter	abdulrehman8833
weight	10000 (100.00%)
Transaction Info	Block #18888587/Trx 04812bd80ca73dd574f00b0602a61d69cca6cf59

View Raw JSON Data

{
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  "op": [
    "vote",
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      "permlink": "h8p9o8ul",
      "voter": "abdulrehman8833",
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  "timestamp": "2018-01-11T16:10:45",
  "trx_id": "04812bd80ca73dd574f00b0602a61d69cca6cf59",
  "trx_in_block": 47,
  "virtual_op": 0
}

abdulrehman8833upvoted (100.00%) @dustvoice / h8p9o8ul

2018/01/11 16:10:45 UTC

18,888,587|5c8b836

author	dustvoice
permlink	h8p9o8ul
voter	abdulrehman8833
weight	10000 (100.00%)
Transaction Info	Block #18888587/Trx 5c8b836ec9151c58a024648d5bba80e0c0499a2a

View Raw JSON Data

{
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      "permlink": "h8p9o8ul",
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  "op_in_trx": 0,
  "timestamp": "2018-01-11T16:10:45",
  "trx_id": "5c8b836ec9151c58a024648d5bba80e0c0499a2a",
  "trx_in_block": 32,
  "virtual_op": 0
}

stopyoutubereplied to @dustvoice / y6i4o69ri

2018/01/11 15:35:18 UTC

18,887,878|25c9d8e

author	stopyoutube
body	I gave you some lovin! How 'bout you give me some too?
json metadata	{"app":"dtube/0.6"}
parent author	dustvoice
parent permlink	h8p9o8ul
permlink	y6i4o69ri
title	y6i4o69ri
Transaction Info	Block #18887878/Trx 25c9d8ed284ad539592f3950198a3245f9f3a56a

View Raw JSON Data

{
  "block": 18887878,
  "op": [
    "comment",
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      "author": "stopyoutube",
      "body": "I gave you some lovin! How 'bout you give me some too?",
      "json_metadata": "{\"app\":\"dtube/0.6\"}",
      "parent_author": "dustvoice",
      "parent_permlink": "h8p9o8ul",
      "permlink": "y6i4o69ri",
      "title": "y6i4o69ri"
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  "timestamp": "2018-01-11T15:35:18",
  "trx_id": "25c9d8ed284ad539592f3950198a3245f9f3a56a",
  "trx_in_block": 52,
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dustvoicereceived 0.053 SBD, 0.011 SP author reward for @dustvoice / re-abhishek77-photography-201814t1942933z-20180104t133603927z

2018/01/11 13:36:06 UTC

18,885,494|virtual

author	dustvoice
permlink	re-abhishek77-photography-201814t1942933z-20180104t133603927z
sbd payout	0.053 SBD
steem payout	0.000 STEEM
vesting payout	18.433100 VESTS
Transaction Info	Block #18885494/Virtual Operation #16

View Raw JSON Data

{
  "block": 18885494,
  "op": [
    "author_reward",
    {
      "author": "dustvoice",
      "permlink": "re-abhishek77-photography-201814t1942933z-20180104t133603927z",
      "sbd_payout": "0.053 SBD",
      "steem_payout": "0.000 STEEM",
      "vesting_payout": "18.433100 VESTS"
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  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-11T13:36:06",
  "trx_id": "0000000000000000000000000000000000000000",
  "trx_in_block": 4294967295,
  "virtual_op": 16
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dustvoicereceived 0.023 SBD, 0.005 SP author reward for @dustvoice / re-givemeyoursteem-the-8-secrets-of-the-happiest-people-20180104t133051960z

2018/01/11 13:30:54 UTC

18,885,390|virtual

author	dustvoice
permlink	re-givemeyoursteem-the-8-secrets-of-the-happiest-people-20180104t133051960z
sbd payout	0.023 SBD
steem payout	0.000 STEEM
vesting payout	8.192490 VESTS
Transaction Info	Block #18885390/Virtual Operation #13

View Raw JSON Data

{
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  "op": [
    "author_reward",
    {
      "author": "dustvoice",
      "permlink": "re-givemeyoursteem-the-8-secrets-of-the-happiest-people-20180104t133051960z",
      "sbd_payout": "0.023 SBD",
      "steem_payout": "0.000 STEEM",
      "vesting_payout": "8.192490 VESTS"
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  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-11T13:30:54",
  "trx_id": "0000000000000000000000000000000000000000",
  "trx_in_block": 4294967295,
  "virtual_op": 13
}

dustvoicereceived 0.004 SP curation reward for @tamsguitar / handycam-photography-euro-trip-random-pics-in-an-around-london-part-i

2018/01/11 13:11:51 UTC

18,885,009|virtual

comment author	tamsguitar
comment permlink	handycam-photography-euro-trip-random-pics-in-an-around-london-part-i
curator	dustvoice
reward	6.144372 VESTS
Transaction Info	Block #18885009/Virtual Operation #16

View Raw JSON Data

{
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  "op": [
    "curation_reward",
    {
      "comment_author": "tamsguitar",
      "comment_permlink": "handycam-photography-euro-trip-random-pics-in-an-around-london-part-i",
      "curator": "dustvoice",
      "reward": "6.144372 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-11T13:11:51",
  "trx_id": "0000000000000000000000000000000000000000",
  "trx_in_block": 4294967295,
  "virtual_op": 16
}

dustvoicereceived 0.001 SP curation reward for @izweed / mistakes-were-made-zg1hbmlh-gftdt

2018/01/11 12:56:30 UTC

18,884,702|virtual

comment author	izweed
comment permlink	mistakes-were-made-zg1hbmlh-gftdt
curator	dustvoice
reward	2.048125 VESTS
Transaction Info	Block #18884702/Virtual Operation #25

View Raw JSON Data

{
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    {
      "comment_author": "izweed",
      "comment_permlink": "mistakes-were-made-zg1hbmlh-gftdt",
      "curator": "dustvoice",
      "reward": "2.048125 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-11T12:56:30",
  "trx_id": "0000000000000000000000000000000000000000",
  "trx_in_block": 4294967295,
  "virtual_op": 25
}

steemdelegated 18.259 SP to @dustvoice

2018/01/08 19:33:09 UTC

18,806,285|d7d3220

delegatee	dustvoice
delegator	steem
vesting shares	29700.586530 VESTS
Transaction Info	Block #18806285/Trx d7d322078df3778ae70e1c6676da8f511c7830b7

View Raw JSON Data

{
  "block": 18806285,
  "op": [
    "delegate_vesting_shares",
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      "delegatee": "dustvoice",
      "delegator": "steem",
      "vesting_shares": "29700.586530 VESTS"
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-08T19:33:09",
  "trx_id": "d7d322078df3778ae70e1c6676da8f511c7830b7",
  "trx_in_block": 10,
  "virtual_op": 0
}

dana-edwardsupvoted (85.55%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/08 04:45:06 UTC

18,788,562|0346fc9

author	dustvoice
permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
voter	dana-edwards
weight	8555 (85.55%)
Transaction Info	Block #18788562/Trx 0346fc94746fd922ef2548c1688634a6acc6eb80

View Raw JSON Data

{
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  "op": [
    "vote",
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      "permlink": "create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required",
      "voter": "dana-edwards",
      "weight": 8555
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  "op_in_trx": 0,
  "timestamp": "2018-01-08T04:45:06",
  "trx_id": "0346fc94746fd922ef2548c1688634a6acc6eb80",
  "trx_in_block": 5,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @dhruv123 / what-steem-price-is-it-a-new-year-gift-do-you-here-a-new-site-just-like-steemit

2018/01/07 18:17:12 UTC

18,776,010|d6725e9

author	dhruv123
permlink	what-steem-price-is-it-a-new-year-gift-do-you-here-a-new-site-just-like-steemit
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18776010/Trx d6725e941aeab5d2807ccc901b50a069d16f00f6

View Raw JSON Data

{
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      "voter": "dustvoice",
      "weight": 10000
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  "op_in_trx": 0,
  "timestamp": "2018-01-07T18:17:12",
  "trx_id": "d6725e941aeab5d2807ccc901b50a069d16f00f6",
  "trx_in_block": 0,
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dustvoiceupvoted (100.00%) @dobartim / competition-for-the-best-yoga-move-the-prize-is-10-sbd-7-days-day-7-the-registration-is-in-progress-last-call-24-hour

2018/01/07 18:16:51 UTC

18,776,003|6094bbe

author	dobartim
permlink	competition-for-the-best-yoga-move-the-prize-is-10-sbd-7-days-day-7-the-registration-is-in-progress-last-call-24-hour
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18776003/Trx 6094bbef962839d39bcc75b248aff8de291de50f

View Raw JSON Data

{
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  "op": [
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      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-07T18:16:51",
  "trx_id": "6094bbef962839d39bcc75b248aff8de291de50f",
  "trx_in_block": 17,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @medicbtom / 64exjn-crypto-trades-for-the-day

2018/01/07 18:16:45 UTC

18,776,001|7ab788a

author	medicbtom
permlink	64exjn-crypto-trades-for-the-day
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18776001/Trx 7ab788a256704c044c413bf1698fd370e1570d03

View Raw JSON Data

{
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      "permlink": "64exjn-crypto-trades-for-the-day",
      "voter": "dustvoice",
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  "op_in_trx": 0,
  "timestamp": "2018-01-07T18:16:45",
  "trx_id": "7ab788a256704c044c413bf1698fd370e1570d03",
  "trx_in_block": 0,
  "virtual_op": 0
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dustvoiceupvoted (100.00%) @alamin0263 / boys-will-understand-zg1hbmlh-9y01q

2018/01/07 18:16:33 UTC

18,775,997|762e2f8

author	alamin0263
permlink	boys-will-understand-zg1hbmlh-9y01q
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18775997/Trx 762e2f87522c15a6c407145027f4e2e9e89d8528

View Raw JSON Data

{
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  "op": [
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      "voter": "dustvoice",
      "weight": 10000
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  "op_in_trx": 0,
  "timestamp": "2018-01-07T18:16:33",
  "trx_id": "762e2f87522c15a6c407145027f4e2e9e89d8528",
  "trx_in_block": 7,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @yuriks2000 / 9lesriuc

2018/01/07 18:16:30 UTC

18,775,996|c483f74

author	yuriks2000
permlink	9lesriuc
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18775996/Trx c483f74e87a7ac010ebd1986dbe05bad2bbdaafe

View Raw JSON Data

{
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  "op": [
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  "op_in_trx": 0,
  "timestamp": "2018-01-07T18:16:30",
  "trx_id": "c483f74e87a7ac010ebd1986dbe05bad2bbdaafe",
  "trx_in_block": 6,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @floprime / happy-new-year

2018/01/07 18:16:24 UTC

18,775,994|c60d3a9

author	floprime
permlink	happy-new-year
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18775994/Trx c60d3a929128df5f708389d8d53400c168392924

View Raw JSON Data

{
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  "op": [
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      "permlink": "happy-new-year",
      "voter": "dustvoice",
      "weight": 10000
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  "op_in_trx": 0,
  "timestamp": "2018-01-07T18:16:24",
  "trx_id": "c60d3a929128df5f708389d8d53400c168392924",
  "trx_in_block": 2,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @dana-edwards / end-game-regulation-the-us-government-will-eventually-demand-require-having-a-license-to-use-cryptocurrency

2018/01/07 18:16:15 UTC

18,775,991|945f05e

author	dana-edwards
permlink	end-game-regulation-the-us-government-will-eventually-demand-require-having-a-license-to-use-cryptocurrency
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18775991/Trx 945f05e550d12bffbd9b8d7eb54a5cd42aa0b788

View Raw JSON Data

{
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  "op": [
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      "permlink": "end-game-regulation-the-us-government-will-eventually-demand-require-having-a-license-to-use-cryptocurrency",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-07T18:16:15",
  "trx_id": "945f05e550d12bffbd9b8d7eb54a5cd42aa0b788",
  "trx_in_block": 49,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @clanbwarclan / they-are-multiplying

2018/01/07 18:16:09 UTC

18,775,989|a3f5666

author	clanbwarclan
permlink	they-are-multiplying
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18775989/Trx a3f56661c57c81d7f5fbb3a855790424a073a358

View Raw JSON Data

{
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  "op": [
    "vote",
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  "op_in_trx": 0,
  "timestamp": "2018-01-07T18:16:09",
  "trx_id": "a3f56661c57c81d7f5fbb3a855790424a073a358",
  "trx_in_block": 38,
  "virtual_op": 0
}

dustvoiceupvoted (100.00%) @jout / german-short-film-english-subtitles-about-people-taking-pictures-of-an-accident-with-a-cruel-twist

2018/01/07 18:15:36 UTC

18,775,978|6f897f7

author	jout
permlink	german-short-film-english-subtitles-about-people-taking-pictures-of-an-accident-with-a-cruel-twist
voter	dustvoice
weight	10000 (100.00%)
Transaction Info	Block #18775978/Trx 6f897f7e80791b8fd2ada3d92513ba62b51e596a

View Raw JSON Data

{
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  "op": [
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      "author": "jout",
      "permlink": "german-short-film-english-subtitles-about-people-taking-pictures-of-an-accident-with-a-cruel-twist",
      "voter": "dustvoice",
      "weight": 10000
    }
  ],
  "op_in_trx": 0,
  "timestamp": "2018-01-07T18:15:36",
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dustvoiceupvoted (100.00%) @vm2904 / how-to-have-fantastic-memory-part-1-original-wildlife-photographs-and-thoughts

2018/01/07 18:15:18 UTC

18,775,972|544bb11

author	vm2904
permlink	how-to-have-fantastic-memory-part-1-original-wildlife-photographs-and-thoughts
voter	dustvoice
weight	10000 (100.00%)
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udin06upvoted (100.00%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 17:34:51 UTC

18,746,404|6058c4a

author	dustvoice
permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
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hurshreplied to @dustvoice / re-dustvoice-re-hursh-7hpiuf-free-re-steem-to-all-my-steemit-friends-20180106t162900741z

2018/01/06 16:29:36 UTC

18,745,099|4109d2d

author	hursh
body	Done
json metadata	{"tags":["resteem"],"app":"steemit/0.1"}
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omrusmanupvoted (100.00%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 14:43:51 UTC

18,742,985|fe1d4e2

author	dustvoice
permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
voter	omrusman
weight	10000 (100.00%)
Transaction Info	Block #18742985/Trx fe1d4e2ca395163217c26db850d0484b728a2bd6

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ubgupvoted (1.00%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 14:08:57 UTC

18,742,288|f44d235

author	dustvoice
permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
voter	ubg
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dustvoicepublished a new post: create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 14:08:54 UTC

18,742,287|1f80156

author	dustvoice
body	# What exactly is a blockchain? - How does a blockchain work? - What is Bitcoin or STEEM exactly? - How does a blockchain make sure of its correctness - What is mining exactly? These are only some questions, probably many of you are asking yourselves. I'm here to provide you with kind of an unusual answer. My goal is to help you undestand the whole system behind blockchains, by actually creating a small blockchain yourself! With the rise of cryptocurrencies and decentralized systems like Bitcoin or STEEM, many people want to really undestand, what this is all about. I will show you how the system works, by coding a blockchain from scratch in python with you. The guide will be mainly for Windows, but I will also add comments regarding Linux. You don't know a whole of python, to follow this guide, but it is advised to know the most basic basics. # Get ready ## Setup Python and pip First off, we need to install Python 3.6+ along with pip, with which you can install python packages. - On Linux, you can install python, by simply typing `sudo apt-get install python3.6` into the terminal. If you encounter errors, please try `sudo apt-get update` and then try to execute the command again. If it still doesn't work, please search for installation instructions for your specific system on your preferred search engine. - On Windows, 1. first download the binary, that suits your system best, under the [official python download page for windows.](https://www.python.org/downloads/windows/). Make sure you grab at least the _version 3.6_ or higher. 2. Install the file you just downloaded. Make sure you check the option to install pip, when provided with an option to do so. If not, don't worry, it probably is enabled by default. ## IDE or not? As a next step, you want to decide, whether to utilize an [IDE](https://en.wikipedia.org/wiki/Integrated_development_environment) or not. An IDE is an environment, which supports you in the creation process of your application, by providing many features, with for example syntax highlighting, or code completion, to name just 2 possible features. My favorite IDE for Python development is probably PyCharm, which you can fetch from [this link.](https://www.jetbrains.com/pycharm) Setting up PyCharm on Windows is as simple, as downloading the executable installer and installing it with the provided setup utility. PyCharm is free tu use, as long as you use the Community Edition. You can also use your coding notepad of choice. We will only work in one file, which you have to execute, so as long as your text-editing software is able to produce files with the ending `.py`, it will work fine. ## Setup your workspace (PyCharm) If you decided to use PyCharm, simply open it up and click on _Create Project_ in the popup dialogue. In the next dialogue you want to specify your project's name. I chose to use _MyBlockChain_ as my project name. Finally click on _create_ in the bottom right corner. On your left hand side, you're now provided with a file tree. 1. Right-Click on the folder which consists of your project's name, in my case _MyBlockChain_ 2. Go to _new_ 3. Finally click on _Python File_ and 4. Define a Filename. I chose `MyBlockChain.py` as my filename. ## Create your file (Simple Text Editor) If you use a simple text editor, just create a file anywhere you like with the file extension `.py`. In my case I chose to use the filename `MyBlockChain.py`. ## Install the needed packages ### PyCharm In PyCharm you can install packages very easily and add them to your project: 1. Make sure, you have your project open 2. Go to _File_ -> _Settings_ -> _Project: [your project name]_ -> _Project Interpreter_ 3. Then click on the green plus symbol. 4. In the search field type in _Flask_ first. Select the first entry, which simply says _Flask_. Then click on Install Package in the bottom left corner. 5. Do the same thing for _Requests_. ### Pip If you chose not to use PyCharm, you simply need to open up the terminal on linux or the command prompt, or PowerShell on Windows _(simply press Windows+R and type in cmd)_ and then execute `pip install Flask==0.12.2 requests==2.18.4 `. If this gives you an error, please double check that you have _pip_ installed. If the problem still occurs, please troubleshoot the error message using google, as there are too many possibilities, what the error could be caused by, for me to discuss every one of them here. ## Getting a HTTP-Client You will also need a HTTP-Client, as we need to make `GET` and `POST` requests to our Flask instance, at some Point in time. Mainly, there are two options - [_Postman_](https://www.getpostman.com/) or [_cURL_](https://curl.haxx.se/). I highly recommend _Postman_, as it is easy and intuitive to use, but if you just want a simple and quick solution, without having to register for an account, just use _cURL_. Online solutions, probably won't work, as the webserver you are going to be trying to access, is just on your local machine. ## Just gimme the source code! If you just want the source code and don't want to follow my instructions, please scroll down, to the very end of this post, where I will add the source code in its complete beauty. # The Blockchain - Your Blockchain ## Step 1: Creating a simplistic Blockchain A block chain is basically a chain of blocks that are linked together in some way, as you have already figured. In this case, every block contains a hash of the previous block. A hash is a hexadecimal number that is determined by a specific algorithm. Imagine a hash being a digital fingerprint of an item. A good hash algorithm will never return the same hash for two different items, so every hash is individual. In our case we will be using the [_SHA-256_](https://en.wikipedia.org/wiki/SHA-2) algorithm. Furthermore the hash algorithm is not reversible, so you can't determine the object, by having its hash, but you can always apply the hash algorithm on the object, to get its hash. As every item has the hash of its previous item, the blockchain is protected against violation, as one would have to change every following block, as the hash changes with every change, as two different items can't have the same hash. ### The Blockchain class Our Blockchain class basically consists of a constructor and some functions. In the constructor, we will create two empty lists - one to store our blockchain in and another, for our transactions. As for now, our class will have several functions: - A function to create new blocks - A function to create new transactions - A function, which hashes a block - A function to fetch the last block The python template looks like this: ```python class MyBlockChain(object): def __init__(self): self.blockchain = [] self.transactions = [] def create_new_block(self): # This function creates a new block and appends it to the chain pass def create_new_transaction(self): # This function creates a new transaction and adds it to the list of transactions pass @staticmethod def hash(block): # This method hashes the passed block pass @property def last_block(self): # This function returns the last block in the chain pass ``` ## Step 2: The blocks As described earlier, a blockchain consists of blocks. So I will cover them first. Each Block has 5 fields: - An index, - an Unix timestamp, - a list of transactions, - a proof, - and finally the hash of the previous block. Just to clarify things, here is an example of a block ```json example_block = { 'index': 5, 'timestamp': 1515110045.123456, 'transactions': [ { 'sender': "154d8554f9541e12354e1234f512a001", 'recipient': "8654e21254c6512a51bce156542d1e5c", 'amount': 212, } ], 'proof': 488612354568, 'previous_hash': "c7be1ed902fb8dd4d48997c6452f5d7e509fbcdbe2808b16bcf4edce4c07d14e" } ``` ## Step 3: Hashing it As every block needs the hash of the previous block, we need a function, that calculates the hash of a block. To accomplish this, we simply modify our empty `hash` function ```python import hashlib import json class MyBlockChain(object): [...] @staticmethod def hash(block): """ This function hashes the block using the SHA-256 hash algorithm The function is given a block and returns a string, consisting of the hash :param block: <dict> Block :return: <str> """ # As every change in an item changes the hash, we first have to do a little sort operation, or else we would get inconsistent hashes block_sorted = json.dumps(block, sort_keys=True).encode() return hashlib.sha256(block_sorted).hexdigest() ``` ## Step 4: Transactions Our `create_new_transaction` method is responsible for adding new transactions to the `transactions` list, which will then be stored inside a block. The whole function is pretty self explanatory. But first we need a function to return the last block of the chain, as we will calculate the new index, at which the transaction will be stored, by increasing the index of the last block by 1 ```python class MyBlockChain(object): [...] @property def last_block(self): return self.blockchain[-1] ``` Now we can fill out the `create_new_transaction` function ```python class MyBlockChain(object): [...] def create_new_transaction(self, sender, recipient, amount): """ This function creates a new transaction that will then be placed in a new block, alone or bundled together with other transactions. :param sender: <str> Sender's address :param recipient: <str> Recipient's address :param amount: <int> Amount to be transferred :return: <int> This is the index of the block that will contain this transaction """ self.transactions.append({ 'sender': sender, 'recipient': recipient, 'amount': amount, }) return self.last_block['index'] + 1 ``` ## Step 5: Creating new Blocks By now we almost have everything at our hands, what we need in order to make a new block. The only thing missing is the _proof_ field. As this is a little harder to understand, I will explain it later. But we still have one problem - if every block has the hash of the previous block, what shall we do with our first block, as there is no previous block for us to hash. This first block is called the _genesis_ block. ```python import hashlib import json from time import time class MyBlockChain(object): def __init__(self): self.blockchain = [] self.transactions = [] # Creation of the mentioned genesis block self.create_new_block(previous_hash=1, proof=100) def create_new_block(self, proof, previous_hash=None): """ Creates a new block and adds it to the blockchain :param proof: <int> This is generated by the proof of work algorithm :param previous_hash: (Optional) <str> Hash of the preleading Block :return: <dict> Return the new block """ new_block = { 'index': len(self.blockchain) + 1, 'timestamp': time(), 'transactions': self.transactions, 'proof': proof, 'previous_hash': previous_hash or self.hash(self.blockchain[-1]), } # As all pending transactions have been processed and added to the block, the list can be resetted self.transactions = [] # Add the new block to the blockchain self.blockchain.append(new_block) return new_block ``` ## Step 6: What's up with the proof?! ### The [Proof of Work (PoW) algorithm](https://en.wikipedia.org/wiki/Proof-of-work_system) This system wants to proof that work has been done. Now a little bit less abstract. Basically we are searching for a number that matches a specific criteria. The thing is, for the system to work, the process of finding a number matching the criteria has to be difficult, but the verification process has to be quick and easy. This is how new blocks are created, or expressed in another, more commonly used term, _mined_. #### Still too abstract? Ok here is an example: We are looking for a hash of a product of two integers that ends with a 1. So the result of the multiplication of `a` and `b` gets hashed and has to end with a 1. If we set a to `a` static value, our algorithm will determine a value for `b`, for which this criteria is matched. ```python from hashlib import sha256 a = 12 b = 0 # We don't know what b has to be. It will be determined by the algorithm while sha256(f'{ab}'.encode()).hexdigest()[-1] != "1": b += 1 print(f'The solution is b = {b}') ``` This example outputs ``` The solution is b = 4 ``` This means that the hash of `124` ends with a 1 ``` hash(48) = 98010bd9270f9b100b6214a21754fd33bdc8d41b2bc9f9dd16ff54d3c34ffd71 ``` As you can tell, the verification process doesn't need countless loops, until it finds a matching pair. You just have to run the hash algorithm once on the numbers and you can easily determine, whether the numbers match the criteria, or not. ## Step 7: Implementing PoW Firstoff, we need a criteria, or commonly referred to as a rule. For now, our rule is that the hash has to have 5 leading zeroes, so `000005bc845e...` would be a valid result, but `000019ea76c4` would not. As the difficulty rises extremely, if we would require 6 leading zeros, the difficulty of our simple algorithm can be adjusted by changing the amount of leading zeroes required. This is the implementation in python: ```python [...] from uuid import uuid4 class MyBlockChain(object): [...] def pow(self, last_proof): """ Simple PoW Algorithm: - Find a number y, so that hash(xy) starts with 5 zeroes. x is the last y aka last_proof. y is then the new proof. :param last_proof: <int> :return: <int> """ current_proof = 0 while self.validate_proof(last_proof, current_proof) is False: current_proof += 1 return current_proof @staticmethod def validate_proof(last_proof, current_proof): """ Returns, whether the hash of the lastproof and the current_proof contains 5 leading zeroes. :param last_proof: <int> Previous Proof Number :param current_proof: <int> Current Proof Number :return: <bool> """ possible_hash = hashlib.sha256(f'{last_proof}{current_proof}'.encode()).hexdigest() return possible_hash[:5] == "00000" ``` ## Step 8: Interacting with our class Now we are able to create a blockchain. But we can't really interact with it, as we have only interacted with the functions and variables of our class. We are going to use HTTP requests to interact with our blockchain. So let's set it up! # HTTP in the house! To talk to our blockchain using Http requests, we need some help - which comes in the form of the _Flask Framework_. We will create and implement 3 basic methods for now: - `/blockchain` to retrieve the full blockchain - `/mining` to make our simple server mine a block - `/transactions/add` to add a new transaction to the blockchain. ## Step 9: Flask First we need to implement Flask. Here is the code: ```python [...] from textwrap import dedent from flask import Flask, jsonify, request class MyBlockChain(object): [...] app = Flask(__name__) node_identifier = str(uuid4()).replace('-', '') myblockchain = MyBlockChain() @app.route('/blockchain', methods=['GET']) def get_full_chain(): output = { 'chain': myblockchain.blockchain, 'length': len(myblockchain.blockchain), } return jsonify(output), 200 @app.route('/mining', methods=['GET']) def mining(): pass @app.route('/transactions/add', methods=['POST']) def add_transaction(): pass if __name__ == '__main__': app.run(host='0.0.0.0', port=5000) ``` ## Step 10: Adding Transactions As this is commonly the main task of a block chain and also required for a new block, I will cover this first. The user sends a _POST request_ to `/transactions/add` with a JSON object, containing all required fields. This is an example, for a possible, valid request: ```json { "sender": "154d8554f9541e12354e1234f512a001", "recipient": "8654e21254c6512a51bce156542d1e5c", "amount": 212 } ``` As you can see, a request has three fields: - A _sender_ field, with the sender id, - a _recipient_ field, with the recipient id - and an amount, which defines how many units are to be transferred Now we just need to implement this function ```python [...] @app.route('/transactions/add', methods=['POST']) def add_transaction(): values = request.get_json() # The POST request has to have the following required fields required = ['sender', 'recipient', 'amount'] if not all(k in values for k in required): return 'There are values missing', 400 # Adds a new transaction by utilizing our function index = myblockchain.create_new_transaction(values['sender'], values['recipient'], values['amount']) output = {'message': f'Your registered Transaction is going to be a part of the block with the index of {index}'} return jsonify(output), 201 ``` This function simply calls the `create_new_transaction` method with the parameters of the POST request ## Step 11: Setup your mines As discussed earlier, future blocks have to be mined. If a new block is found/mined, all pending transactions are added to this block. To 'mine' a new block, our function hast to do three things 1. Calculate the proof 2. Reward the miner with a specific amount of coins (in our example 1 coin) 3. Add the new mined block to the blockchain _(The fact that the recipient is our current node, will make more sense, as we will talk about decentralization later on.)_ ```python @app.route('/mining', methods=['GET']) def mining(): # Calculate the new proof by using our PoW algorithm last_block = myblockchain.last_block last_proof = last_block['proof'] proof = myblockchain.pow(last_proof) # For finding/mining the proof, the miner is granted a reward # The sender is nobody, as this coin is coming out of the void myblockchain.create_new_transaction( sender="0", recipient=node_identifier, amount=1, ) # Add the new created block to the chain previous_hash = myblockchain.hash(last_block) newblock = myblockchain.create_new_block(proof, previous_hash) output = { 'message': "A new block was mined", 'index': newblock['index'], 'transactions': newblock['transactions'], 'proof': newblock['proof'], 'previous_hash': newblock['previous_hash'], } return jsonify(output), 200 ``` # Hello World! Now, finally we will be interacting with our blockchain API. Grab your HTTP client of choice and get going! I will explain the procedure for Postman and cURL. ## Step 12: Start up the chain First off fire up your server. In PyCharm simply click on _Run_ -> _Run..._ and select _[your filename].py_ as the file to run, in my case _myblockchain.py_. If you chose to use a simple python file without an IDE, fire up a terminal or command prompt window inside the directory your file is located in and execute the following command ``` python blockchain.py ``` as a result you will see something similar to this ``` $ python blockchain.py * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit) ``` Note that you may be prompted with a dialogue of your firewall. Just accept it. ## Step 13: Mining it all! Ok let's try the most exciting thing first, mining. I'm sure you can't wait to mine your first block, so let's do it! As you can see in the code ```python [...] @app.route('/mining', methods=['GET']) def mining(): [...] ``` we will be interacting with the `mining` part of our API through `GET` requests. This makes sense, as our only goal with this part of the API is, to mine a new block. We don't have to pass anything to the function at all, so a `GET` request is the way to go. ### Postman If you chose to use Postman, here is a quick tutorial on how to make a post request. 1. First you have to register for an account, if you haven't already done that 2. and login after that. 3. If you are logged in, you shoudl be provided with several options such as _Request_, _Collection_, _Environment_. 4. You could simply use the option _Request_, but to keep things organized, we are going to select the _Collection_ option. 5. After that simply choose a name for your collection, in my case I'm using _MyBlockChain_ as my name. 6. Now click on the _New_ Button, located in the top left corner and select _Request_ this time. We are now going to be creating 3 requests. 7. The first request is going to be our _mining_ request, second is a _new transaction_ request and finally we will have a _get whole blockchain_ request. Of course you can customize the request names as you like. 8. Make sure, as you create these 3 requests, that you select our newly created Collection in the bottom section of the dialogue! 9. Now click on our Collection's folder in the left sidebar. You should see your 3 newly created requests. Select the _mining_ request first. 10. On the right you are now provided with an interface. As you can see by the selected item from the dropdown box, left to the text field, a `GET` request is the standard request type, so we don't have to change that yet. 11. In the text field `Enter request URL` we are now going to enter the `mining` URL of our API, so enter `http://localhost:5000/mining` as the request URL. ### cURL If you chose to use cURL as your HTTP client, simply type `curl -i -H "Content-Type: application/json" -X GET http://localhost:5000/mining` in a terminal window ### Either way With both methods you should see something similar to this as a result ```json { "index": 2, "message": "New Block Forged", "previous_hash": "0f9cb2f06100899cb31b85fef221e243d1088c0aa6840a568e58d4a27dbd186a", "proof": 888273, "transactions": [ { "amount": 1, "recipient": "491002ea048a42609d967027cc46a07b", "sender": "0" } ] } ``` ## Step 14: Transactions are great! As our mining algorithm seems to be working fine, let's create a new transaction, to be stored in a fresh mined block. To do that in ### Postman 1. Click on the _new transaction_ request in the left sidebar. 2. Click on the _GET_ button with the small arrow pointing down. 3. Select _POST_ from the drop-down list. 4. In the navbar below the text field, select _Body_ 5. and then mark the _raw_ option. 6. You should now be provided with an editor like text area, and another drop-down menu next to the _binary_ option, where _Text_ is currently selected. Select _JSON (application/json)_ from this list. 7. Now type in the following into the text area. ```json { "sender": "your-node-address", "recipient": "another-node-address", "amount": 212 } ``` ### cURL Just execute `curl -X POST -H "Content-Type: application/json" -d '{"sender": "your-node-address", "recipient": "another-node-address", "amount": 212}' "http://localhost:5000/transactions/add"` in a terminal window. ### In both cases Replace `your-node-address` with the _recipient_ address from you mining request, as this is your node address. You can also select any other 32 digit hexadezimal number, for now. Furthermore replace `another-node-address` with a random 32 digit hexadezimal number for now, as we currently don't have any other nodes. Adjust the `amount` to your liking. And voilà! You have registered your first transaction! ## Step 15: The Chain... So let's inspect our chain! If you're using ### Postman Click on the _get whole blockchain_ request in the left sidebar and simply enter `http://localhost:5000/blockchain` in the `Enter request URL` text field, as _GET_ should be preselected. If not, please change it to the _GET_ option. ### cURL just execute `curl -i -H "Content-Type: application/json" -X GET http://localhost:5000/blockchain` in a terminal window. ### Either way you should get your whole blockchain in form of a JSON-Object. In my case, my blockchain looks like this, after mining 2 times, adding 3 transactions and mining another block: ```json { "chain": [ { "index": 1, "previous_hash": "1", "proof": 100, "timestamp": 1515156902.4502413, "transactions": [] }, { "index": 2, "previous_hash": "0f9cb2f06100899cb31b85fef221e243d1088c0aa6840a568e58d4a27dbd186a", "proof": 888273, "timestamp": 1515156913.2686973, "transactions": [ { "amount": 1, "recipient": "491002ea048a42609d967027cc46a07b", "sender": "0" } ] }, { "index": 3, "previous_hash": "1d2ae4a41f4a82ce6f04944e8227bf9c4d951d560f8763b910d7314634dfe09c", "proof": 1156297, "timestamp": 1515158367.3596537, "transactions": [ { "amount": 212, "recipient": "d4ee26eee15148ee92c6cd394edd974e", "sender": "491002ea048a42609d967027cc46a07b" }, { "amount": 212, "recipient": "5654c5654e1b551a65e15f5e4651c156", "sender": "491002ea048a42609d967027cc46a07b" }, { "amount": 111, "recipient": "491002ea048a42609d967027cc46a07b", "sender": "5654c5654e1b551a65e15f5e4651c156" }, { "amount": 1, "recipient": "491002ea048a42609d967027cc46a07b", "sender": "0" } ] } ], "length": 3 } ``` # Decentralizing it Ok, so we got a blockchain, that's working fine and we can interact with it. But one very important thing is still missing: Decentralization. This is a core element of the blockchain idea. First off by decentralizing the whole thing, safety and integrity of the blockchain is guaranteed, as a change in the blockchain will be recognized, by the other nodes, as they also have a copy of the blockchain, and discarded. The second reason is that we somehow have to make sense of our transactions. For this we need other nodes and why shouldn't they contribute to our network, by being a part of the blockchain system?! But we still have a conflict there: What if a node has a blockchain that differs from all the others? For our simple blockchain we will always make the longest valid blockchain authorative. ## Step 16: Someone out there?! But first things first. To get started, we first have to implement other nodes into our system. To accomplish this task, we have to adjust a few things in our API. First off, we are going to implement some new endpoints: 1. `/nodes/add` to add new nodes in form of a list of URLs 2. `/nodes/resolve` to resolve the conflict we discussed previously by using a consensus algorithm. To do this, we have to modify our Blockchain class first: ```python [...] from urllib.parse import urlparse class MyBlockChain(object): def __init__(self): [...] self.nodes = set() def add_node(self, address): """ Register a new node :param address: <str> This is the new node's address, for example 'http://192.168.1.112:5000' :return: None """ node_url = urlparse(address) self.nodes.add(node_url.netloc) ``` ## Step 17: We need Consensus To resolve the conflict of differing blockchains between the nodes, we are going to implement a consensus algorithm. As we discussed earlier, we are always utilizing the longest valid blockchain. First we are implementing a function that validates a blockchain: ```python [...] import requests class MyBlockChain(object) [...] def validate_blockchain(self, test_chain): """ Evaluate, whether a blockchain is valid :param chain: <list> The blockchain that shall be tested :return: <bool> Returns true if the blockchain is valid """ last_block = test_chain[0] current_index = 1 while current_index < len(test_chain): block = test_chain[current_index] # Determine, whether the hash is correct if block['previous_hash'] != self.hash(last_block): return False # Determine, wheter the proof of work is correct if not self.validate_proof(last_block['proof'], block['proof']): return False last_block = block current_index += 1 return True ``` Now we just have to run every blockchain in our surrounding network through this consensus algorithm: ```python [...] class MyBlockChain(object) [...] def resolve(self): """ This algorithm resolves conflicts between our nodes. It is the consensus algorithm which I mentioned previously. :return: <bool> Returns true, if our chain was substituted with an updated version """ surrounding_nodes = self.nodes updated_chain = None # If we follow our consensus algorithm description, we only want blockchains that are longer, than our current chain max_length = len(self.blockchain) # Iterate every surrounding nodes in our network through the consensus algorithm, which means checking if the node's blockchain is longer than our current blockchain and valid and set it as our new blockchain and continue checking, as there could be an even longer and valid blockchain. for node_iterator in surrounding_nodes: response = requests.get(f'http://{node_iterator}/blockchain') if response.status_code == 200: length = response.json()['length'] chain_iterator = response.json()['chain'] if length > max_length and self.validate_blockchain(chain_iterator): max_length = length updated_chain = chain_iterator # If we found a new blockchain, replace our current blockchain with the new one if updated_chain: self.blockchain = updated_chain return True return False ``` Now we just have to register our new functions as new endpoints in the API: ```python @app.route('/nodes/add', methods=['POST']) def add_nodes(): values = request.get_json() nodes = values.get('nodes') if nodes is None: return "You didn't post a valid list of nodes. Please double check your input!", 400 for node in nodes: myblockchain.add_node(node) response = { 'message': 'All of your specified nodes have been added to the network!', 'total_nodes': list(myblockchain.nodes), } return jsonify(response), 201 @app.route('/nodes/resolve', methods=['GET']) def consensus(): replaced = myblockchain.resolve() if replaced: response = { 'message': 'There was a longer valid chain within the network. The blockchain of this node has been replaced.', 'new_chain': myblockchain.blockchain } else: response = { 'message': 'The blockchain of this node is already the longest valid chain within the network.', 'chain': myblockchain.blockchain } return jsonify(response), 200 ``` ## Step 18: Friends are great. Even if they're virtual... To test our decentralization algorithms, either grab some friends, to run some nodes for you, or just run the same program on different ports, so you would have to start up an instance of our blockchain-program, then change to port to 5001 for example, save, fire up an instance of this _modified_ program, change the port to 5002, etc. ## Step 19: Add them to your friends list If you got some instances, you just have to register them. To do this, simply send a `POST` request with the following content ```json { "nodes": ["http://[ip-of-another-node-or-127.0.0.1-for-your-local-machine]:[the-port-number]"] } ``` to `http://[the-node-ip-you-want-to-register-it-to]:[port]/nodes/add` ## Step 20: Consensus check After that try to mine some blocks and even add some transactions on let's say node 2 and then run `http://[a-node-ip]:[port]/nodes/resolve` on let's say node 1. The consensus algorithm should step into action and update the blockchain of node 1. # The whole thang I keep my promises ```python import hashlib import json import requests from time import time from uuid import uuid4 from textwrap import dedent from flask import Flask, jsonify, request from urllib.parse import urlparse class MyBlockChain(object): def __init__(self): self.blockchain = [] self.transactions = [] # Creation of the mentioned genesis block self.create_new_block(previous_hash=1, proof=100) self.nodes = set() def create_new_block(self, proof, previous_hash=None): """ Creates a new block and adds it to the blockchain :param proof: <int> This is generated by the proof of work algorithm :param previous_hash: (Optional) <str> Hash of the preleading Block :return: <dict> Return the new block """ new_block = { 'index': len(self.blockchain) + 1, 'timestamp': time(), 'transactions': self.transactions, 'proof': proof, 'previous_hash': previous_hash or self.hash(self.blockchain[-1]), } # As all pending transactions have been processed and added to the block, the list can be resetted self.transactions = [] # Add the new block to the blockchain self.blockchain.append(new_block) return new_block def create_new_transaction(self, sender, recipient, amount): """ This function creates a new transaction that will then be placed in a new block, alone or bundled together with other transactions. :param sender: <str> Sender's address :param recipient: <str> Recipient's address :param amount: <int> Amount to be transferred :return: <int> This is the index of the block that will contain this transaction """ self.transactions.append({ 'sender': sender, 'recipient': recipient, 'amount': amount, }) return self.last_block['index'] + 1 @staticmethod def hash(block): """ This function hashes the block using the SHA-256 hash algorithm The function is given a block and returns a string, consisting of the hash :param block: <dict> Block :return: <str> """ # As every change in an item changes the hash, we first have to do a little sort operation, or else we would get inconsistent hashes block_sorted = json.dumps(block, sort_keys=True).encode() return hashlib.sha256(block_sorted).hexdigest() @property def last_block(self): return self.blockchain[-1] def pow(self, last_proof): """ Simple PoW Algorithm: - Find a number y, so that hash(xy) starts with 5 zeroes. x is the last y aka last_proof. y is then the new proof. :param last_proof: <int> :return: <int> """ current_proof = 0 while self.validate_proof(last_proof, current_proof) is False: current_proof += 1 return current_proof @staticmethod def validate_proof(last_proof, current_proof): """ Returns, whether the hash of the lastproof and the current_proof contains 5 leading zeroes. :param last_proof: <int> Previous Proof Number :param current_proof: <int> Current Proof Number :return: <bool> """ possible_hash = hashlib.sha256(f'{last_proof}{current_proof}'.encode()).hexdigest() return possible_hash[:5] == "00000" def add_node(self, address): """ Register a new node :param address: <str> This is the new node's address, for example 'http://192.168.1.112:5000' :return: None """ node_url = urlparse(address) self.nodes.add(node_url.netloc) def validate_blockchain(self, test_chain): """ Evaluate, whether a blockchain is valid :param chain: <list> The blockchain that shall be tested :return: <bool> Returns true if the blockchain is valid """ last_block = test_chain[0] current_index = 1 while current_index < len(test_chain): block = test_chain[current_index] # Determine, whether the hash is correct if block['previous_hash'] != self.hash(last_block): return False # Determine, wheter the proof of work is correct if not self.validate_proof(last_block['proof'], block['proof']): return False last_block = block current_index += 1 return True def resolve(self): """ This algorithm resolves conflicts between our nodes. It is the consensus algorithm which I mentioned previously. :return: <bool> Returns true, if our chain was substituted with an updated version """ surrounding_nodes = self.nodes updated_chain = None # If we follow our consensus algorithm description, we only want blockchains that are longer, than our current chain max_length = len(self.blockchain) # Iterate every surrounding nodes in our network through the consensus algorithm, which means checking if the node's blockchain is longer than our current blockchain and valid and set it as our new blockchain and continue checking, as there could be an even longer and valid blockchain. for node_iterator in surrounding_nodes: response = requests.get(f'http://{node_iterator}/blockchain') if response.status_code == 200: length = response.json()['length'] chain_iterator = response.json()['chain'] if length > max_length and self.validate_blockchain(chain_iterator): max_length = length updated_chain = chain_iterator # If we found a new blockchain, replace our current blockchain with the new one if updated_chain: self.blockchain = updated_chain return True return False app = Flask(__name__) node_identifier = str(uuid4()).replace('-', '') myblockchain = MyBlockChain() @app.route('/blockchain', methods=['GET']) def get_full_chain(): output = { 'chain': myblockchain.blockchain, 'length': len(myblockchain.blockchain), } return jsonify(output), 200 @app.route('/mining', methods=['GET']) def mining(): # Calculate the new proof by using our PoW algorithm last_block = myblockchain.last_block last_proof = last_block['proof'] proof = myblockchain.pow(last_proof) # For finding/mining the proof, the miner is granted a reward # The sender is nobody, as this coin is coming out of the void myblockchain.create_new_transaction( sender="0", recipient=node_identifier, amount=1, ) # Add the new created block to the chain previous_hash = myblockchain.hash(last_block) newblock = myblockchain.create_new_block(proof, previous_hash) output = { 'message': "A new block was mined", 'index': newblock['index'], 'transactions': newblock['transactions'], 'proof': newblock['proof'], 'previous_hash': newblock['previous_hash'], } return jsonify(output), 200 @app.route('/transactions/add', methods=['POST']) def add_transaction(): values = request.get_json() # The POST request has to have the following required fields required = ['sender', 'recipient', 'amount'] if not all(k in values for k in required): return 'There are values missing', 400 # Adds a new transaction by utilizing our function index = myblockchain.create_new_transaction(values['sender'], values['recipient'], values['amount']) output = {'message': f'Your registered Transaction is going to be a part of the block with the index of {index}'} return jsonify(output), 201 @app.route('/nodes/add', methods=['POST']) def add_nodes(): values = request.get_json() nodes = values.get('nodes') if nodes is None: return "You didn't post a valid list of nodes. Please double check your input!", 400 for node in nodes: myblockchain.add_node(node) response = { 'message': 'All of your specified nodes have been added to the network!', 'total_nodes': list(myblockchain.nodes), } return jsonify(response), 201 @app.route('/nodes/resolve', methods=['GET']) def consensus(): replaced = myblockchain.resolve() if replaced: response = { 'message': 'There was a longer valid chain within the network. The blockchain of this node has been replaced.', 'new_chain': myblockchain.blockchain } else: response = { 'message': 'The blockchain of this node is already the longest valid chain within the network.', 'chain': myblockchain.blockchain } return jsonify(response), 200 if __name__ == '__main__': app.run(host='0.0.0.0', port=5000) ``` # Final thoughts And there you have it! Your very own blockchain. Wasn't very hard, was it? I sincerely hope you had fun thorughout this tutorial and were able to understand the concept and system behind it better. If you have any questions, please ask them in the comments and I'll try my best to answer them. # The obligatory begging As this whole tutorial took me over 2 days to finish, I would love to see a lot of comments and feedback under this post. Also if you find any typos, grammar mistakes, etc. and care to tell me, i would be mor than happy about it, as English is not my native language. So please excuse any mistakes I made. I tried my very best. Of course please upvote, if you worship my effort to enrich the community, and if you want to see more such content, consider following me. I wish you only the best - See ya!
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parent author
parent permlink	steemit
permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
title	Create your own blockchain & cryptocurrency! - understand blockchains by creating one in python - no knowledge required
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      "author": "dustvoice",
      "body": "# What exactly is a blockchain?\n- How does a blockchain work?\n- What is Bitcoin or STEEM exactly?\n- How does a blockchain make sure of its correctness\n- What is **mining** exactly?\n\n**These are only some questions, probably many of you are asking yourselves. \nI'm here to provide you with kind of an unusual answer.\nMy goal is to help you undestand the whole system behind blockchains, by actually creating a small blockchain yourself!**\n\nWith the rise of cryptocurrencies and decentralized systems like Bitcoin or STEEM, many people want to really undestand, what this is all about. I will show you how the system works, by coding a blockchain from scratch in python with you. The guide will be mainly for Windows, but I will also add comments regarding Linux. You don't know a whole of python, to follow this guide, but it is advised to know the most basic basics.\n\n# Get ready\n## Setup Python and pip\nFirst off, we need to install Python 3.6+ along with pip, with which you can install python packages. \n- On **Linux**, you can install python, by simply typing `sudo apt-get install python3.6` into the terminal. If you encounter errors, please try `sudo apt-get update` and then try to execute the command again. If it still doesn't work, please search for installation instructions for your specific system on your preferred search engine.\n- On **Windows**,\n  1. first download the binary, that suits your system best, under the [official python download page for windows.](https://www.python.org/downloads/windows/). Make sure you grab at least the _version 3.6_ or higher.\n  2. Install the file you just downloaded. Make sure you check the option to install pip, when provided with an option to do so. If not, don't worry, it probably is enabled by default.\n\n## IDE or not?\nAs a next step, you want to decide, whether to utilize an [IDE](https://en.wikipedia.org/wiki/Integrated_development_environment) or not. An IDE is an environment, which supports you in the creation process of your application, by providing many features, with for example syntax highlighting, or code completion, to name just 2 possible features. My favorite IDE for Python development is probably PyCharm, which you can fetch from [this link.](https://www.jetbrains.com/pycharm) Setting up PyCharm on Windows is as simple, as downloading the executable installer and installing it with the provided setup utility. PyCharm is free tu use, as long as you use the Community Edition.\nYou can also use your coding notepad of choice. We will only work in one file, which you have to execute, so as long as your text-editing software is able to produce files with the ending `.py`, it will work fine.\n\n## Setup your workspace (PyCharm)\nIf you decided to use PyCharm, simply open it up and click on _Create Project_ in the popup dialogue. In the next dialogue you want to specify your project's name. I chose to use _MyBlockChain_ as my project name. Finally click on _create_ in the bottom right corner. On your left hand side, you're now provided with a file tree. \n1. Right-Click on the folder which consists of your project's name, in my case _MyBlockChain_\n2. Go to _new_ \n3. Finally click on _Python File_ and\n4. Define a Filename. I chose `MyBlockChain.py` as my filename.\n\n## Create your file (Simple Text Editor)\nIf you use a simple text editor, just create a file anywhere you like with the file extension `.py`. In my case I chose to use the filename `MyBlockChain.py`.\n\n## Install the needed packages\n### PyCharm\nIn PyCharm you can install packages very easily and add them to your project:\n1. Make sure, you have your project open\n2. Go to _File_ -> _Settings_ -> _Project: [your project name]_ -> _Project Interpreter_\n3. Then click on the green plus symbol.\n4. In the search field type in _Flask_ first. Select the first entry, which simply says _Flask_. Then click on Install Package in the bottom left corner.\n5. Do the same thing for _Requests_.\n### Pip\nIf you chose not to use PyCharm, you simply need to open up the terminal on linux or the command prompt, or PowerShell on Windows _(simply press **Windows+R** and type in cmd)_ and then execute `pip install Flask==0.12.2 requests==2.18.4 `. If this gives you an error, please double check that you have _pip_ installed. If the problem still occurs, please troubleshoot the error message using google, as there are too many possibilities, what the error could be caused by, for me to discuss every one of them here.\n\n## Getting a HTTP-Client\nYou will also need a HTTP-Client, as we need to make `GET` and `POST` requests to our Flask instance, at some Point in time. Mainly, there are two options - [_Postman_](https://www.getpostman.com/) or [_cURL_](https://curl.haxx.se/). I highly recommend _Postman_, as it is easy and intuitive to use, but if you just want a simple and quick solution, without having to register for an account, just use _cURL_. Online solutions, probably won't work, as the webserver you are going to be trying to access, is just on your local machine. \n\n## Just gimme the source code!\nIf you just want the source code and don't want to follow my instructions, please scroll down, to the very end of this post, where I will add the source code in its complete beauty.\n\n# The Blockchain - Your Blockchain\n## Step 1: Creating a simplistic Blockchain\nA block chain is basically a chain of blocks that are linked together in some way, as you have already figured. In this case, every block contains a hash of the previous block. A hash is a hexadecimal number that is determined by a specific algorithm. Imagine a hash being a digital fingerprint of an item. A good hash algorithm will never return the same hash for two different items, so every hash is individual. In our case we will be using the [_SHA-256_](https://en.wikipedia.org/wiki/SHA-2) algorithm. Furthermore the hash algorithm is not reversible, so you can't determine the object, by having its hash, but you can always apply the hash algorithm on the object, to get its hash. As every item has the hash of its previous item, the blockchain is protected against violation, as one would have to change every following block, as the hash changes with every change, as two different items can't have the same hash.\n### The Blockchain class\nOur Blockchain class basically consists of a constructor and some functions. In the constructor, we will create two empty lists - one to store our blockchain in and another, for our transactions. As for now, our class will have several functions:\n- A function to create new blocks\n- A function to create new transactions\n- A function, which hashes a block\n- A function to fetch the last block\nThe python template looks like this:\n```python\nclass MyBlockChain(object):\n    def __init__(self):\n        self.blockchain = []\n        self.transactions = []\n        \n    def create_new_block(self):\n        # This function creates a new block and appends it to the chain\n        pass\n    \n    def create_new_transaction(self):\n        # This function creates a new transaction and adds it to the list of transactions\n        pass\n    \n    @staticmethod\n    def hash(block):\n        # This method hashes the passed block\n        pass\n\n    @property\n    def last_block(self):\n        # This function returns the last block in the chain\n        pass\n```\n## Step 2: The blocks\nAs described earlier, a blockchain consists of blocks. So I will cover them first.\nEach Block has 5 fields:\n- An index,\n- an Unix timestamp,\n- a list of transactions,\n- a proof,\n- and finally the hash of the previous block.\nJust to clarify things, here is an example of a block\n```json\nexample_block = {\n    'index': 5,\n    'timestamp': 1515110045.123456,\n    'transactions': \n    [\n        {\n            'sender': \"154d8554f9541e12354e1234f512a001\",\n            'recipient': \"8654e21254c6512a51bce156542d1e5c\",\n            'amount': 212,\n        }\n    ],\n    'proof': 488612354568,\n    'previous_hash': \"c7be1ed902fb8dd4d48997c6452f5d7e509fbcdbe2808b16bcf4edce4c07d14e\"\n}\n```\n## Step 3: Hashing it\nAs every block needs the hash of the previous block, we need a function, that calculates the hash of a block. To accomplish this, we simply modify our empty `hash` function\n```python\nimport hashlib\nimport json\n\nclass MyBlockChain(object):\n    [...]\n    @staticmethod\n    def hash(block):\n        \"\"\"\n        This function hashes the block using the SHA-256 hash algorithm\n        The function is given a block and returns a string, consisting of the hash\n        :param block: <dict> Block\n        :return: <str>\n        \"\"\"\n\n        # As every change in an item changes the hash, we first have to do a little sort operation, or else we would get inconsistent hashes\n        block_sorted = json.dumps(block, sort_keys=True).encode()\n        return hashlib.sha256(block_sorted).hexdigest()\n```\n## Step 4: Transactions\nOur `create_new_transaction` method is responsible for adding new transactions to the `transactions` list, which will then be stored inside a block. The whole function is pretty self explanatory. But first we need a function to return the last block of the chain, as we will calculate the new index, at which the transaction will be stored, by increasing the index of the last block by 1\n```python\nclass MyBlockChain(object):\n    [...]\n    @property\n    def last_block(self):\n        return self.blockchain[-1]\n```\nNow we can fill out the `create_new_transaction` function\n```python\nclass MyBlockChain(object):\n    [...]\n    def create_new_transaction(self, sender, recipient, amount):\n        \"\"\"\n        This function creates a new transaction that will then be placed in a new block, alone or bundled together with other transactions.\n        \n        :param sender: <str> Sender's address\n        :param recipient: <str> Recipient's address\n        :param amount: <int> Amount to be transferred\n        :return: <int> This is the index of the block that will contain this transaction\n        \"\"\"\n\n        self.transactions.append({\n            'sender': sender,\n            'recipient': recipient,\n            'amount': amount,\n        })\n\n        return self.last_block['index'] + 1\n```\n## Step 5: Creating new Blocks\nBy now we almost have everything at our hands, what we need in order to make a new block. The only thing missing is the _proof_ field. As this is a little harder to understand, I will explain it later. \nBut we still have one problem - if every block has the hash of the previous block, what shall we do with our first block, as there is no previous block for us to hash. \nThis first block is called the _genesis_ block.\n```python\nimport hashlib\nimport json\nfrom time import time\n\nclass MyBlockChain(object):\n    def __init__(self):\n        self.blockchain = []\n        self.transactions = []\n\n        # Creation of the mentioned genesis block\n        self.create_new_block(previous_hash=1, proof=100)\n\n    def create_new_block(self, proof, previous_hash=None):\n        \"\"\"\n        Creates a new block and adds it to the blockchain\n        :param proof: <int> This is generated by the proof of work algorithm\n        :param previous_hash: (Optional) <str> Hash of the preleading Block\n        :return: <dict> Return the new block\n        \"\"\"\n\n        new_block = {\n            'index': len(self.blockchain) + 1,\n            'timestamp': time(),\n            'transactions': self.transactions,\n            'proof': proof,\n            'previous_hash': previous_hash or self.hash(self.blockchain[-1]),\n        }\n\n        # As all pending transactions have been processed and added to the block, the list can be resetted\n        self.transactions = []\n        \n        # Add the new block to the blockchain\n        self.blockchain.append(new_block)\n        return new_block\n```\n##  Step 6: What's up with the proof?!\n### The [Proof of Work (PoW) algorithm](https://en.wikipedia.org/wiki/Proof-of-work_system)\nThis system wants to **proof** that work has been done. Now a little bit less abstract. Basically we are searching for a number that matches a specific criteria. The thing is, for the system to work, the process of finding a number matching the criteria has to be **difficult**, but the verification process has to be **quick and easy**. This is how new blocks are created, or expressed in another, more commonly used term, _mined_.\n#### Still too abstract? Ok here is an example:\nWe are looking for a hash of a product of two integers that ends with a 1.\nSo the result of the multiplication of `a` and `b` gets hashed and has to end with a 1. If we set a to `a` static value, our algorithm will determine a value for `b`, for which this criteria is matched. \n```python\nfrom hashlib import sha256\na = 12\nb = 0  # We don't know what b has to be. It will be determined by the algorithm\nwhile sha256(f'{a*b}'.encode()).hexdigest()[-1] != \"1\":\n    b += 1\nprint(f'The solution is b = {b}')\n```\nThis example outputs\n```\nThe solution is b = 4\n```\nThis means that the hash of `12*4` ends with a 1\n```\nhash(48) = 98010bd9270f9b100b6214a21754fd33bdc8d41b2bc9f9dd16ff54d3c34ffd71\n```\nAs you can tell, the verification process doesn't need countless loops, until it finds a matching pair. You just have to run the hash algorithm once on the numbers and you can easily determine, whether the numbers match the criteria, or not.\n## Step 7: Implementing PoW\nFirstoff, we need a criteria, or commonly referred to as a rule. For now, our rule is that the hash has to have 5 leading zeroes, so `000005bc845e...` would be a valid result, but `000019ea76c4` would not. As the difficulty rises extremely, if we would require 6 leading zeros, the difficulty of our simple algorithm can be adjusted by changing the amount of leading zeroes required. This is the implementation in python:\n```python\n[...]\nfrom uuid import uuid4\n\nclass MyBlockChain(object):\n    [...]\n        \n    def pow(self, last_proof):\n        \"\"\"\n        Simple PoW Algorithm:\n         - Find a number y, so that hash(xy) starts with 5 zeroes. x is the last y aka last_proof. y is then the new proof.\n        :param last_proof: <int>\n        :return: <int>\n        \"\"\"\n        \n        current_proof = 0\n        while self.validate_proof(last_proof, current_proof) is False:\n            current_proof += 1\n\n        return current_proof\n\n    @staticmethod\n    def validate_proof(last_proof, current_proof):\n        \"\"\"\n        Returns, whether the hash of the lastproof and the current_proof contains 5 leading zeroes.\n        :param last_proof: <int> Previous Proof Number\n        :param current_proof: <int> Current Proof Number\n        :return: <bool>\n        \"\"\"\n\n        possible_hash = hashlib.sha256(f'{last_proof}{current_proof}'.encode()).hexdigest()\n        return possible_hash[:5] == \"00000\"\n```\n## Step 8: Interacting with our class\nNow we are able to create a blockchain. But we can't really interact with it, as we have only interacted with the functions and variables of our class.\nWe are going to use HTTP requests to interact with our blockchain. So let's set it up!\n# HTTP in the house!\nTo talk to our blockchain using Http requests, we need some help - which comes in the form of the _Flask Framework_. We will create and implement 3 basic methods for now:\n- `/blockchain` to retrieve the full blockchain\n- `/mining` to make our simple server mine a block\n- `/transactions/add` to add a new transaction to the blockchain.\n## Step 9: Flask\nFirst we need to implement Flask. Here is the code:\n```python\n[...]\nfrom textwrap import dedent\nfrom flask import Flask, jsonify, request\n\nclass MyBlockChain(object):\n    [...]\n    \napp = Flask(__name__)\nnode_identifier = str(uuid4()).replace('-', '')\n\nmyblockchain = MyBlockChain()\n\[email protected]('/blockchain', methods=['GET'])\ndef get_full_chain():\n    output = {\n        'chain': myblockchain.blockchain,\n        'length': len(myblockchain.blockchain),\n    }\n    return jsonify(output), 200\n\[email protected]('/mining', methods=['GET'])\ndef mining():\n    pass\[email protected]('/transactions/add', methods=['POST'])\ndef add_transaction():\n    pass\nif __name__ == '__main__':\n    app.run(host='0.0.0.0', port=5000)\n```\n## Step 10: Adding Transactions\nAs this is commonly the main task of a block chain and also required for a new block, I will cover this first. The user sends a _POST request_ to `/transactions/add` with a JSON object, containing all required fields. This is an example, for a possible, valid request:\n```json\n{\n \"sender\": \"154d8554f9541e12354e1234f512a001\",\n \"recipient\": \"8654e21254c6512a51bce156542d1e5c\",\n \"amount\": 212\n}\n```\nAs you can see, a request has three fields:\n- A _sender_ field, with the sender id,\n- a _recipient_ field, with the recipient id\n- and an amount, which defines how many units are to be transferred\nNow we just need to implement this function\n```python\n[...]\n\[email protected]('/transactions/add', methods=['POST'])\ndef add_transaction():\n    values = request.get_json()\n\n    # The POST request has to have the following required fields\n    required = ['sender', 'recipient', 'amount']\n    if not all(k in values for k in required):\n        return 'There are values missing', 400\n\n    # Adds a new transaction by utilizing our function\n    index = myblockchain.create_new_transaction(values['sender'], values['recipient'], values['amount'])\n\n    output = {'message': f'Your registered Transaction is going to be a part of the block with the index of {index}'}\n    return jsonify(output), 201\n```\nThis function simply calls the `create_new_transaction` method with the parameters of the POST request\n## Step 11: Setup your mines\nAs discussed earlier, future blocks have to be mined. If a new block is found/mined, all pending transactions are added to this block. To 'mine' a new block, our function hast to do three things\n1. Calculate the proof\n2. Reward the miner with a specific amount of coins (in our example 1 coin)\n3. Add the new mined block to the blockchain\n_(The fact that the recipient is our current node, will make more sense, as we will talk about decentralization later on.)_\n```python\[email protected]('/mining', methods=['GET'])\ndef mining():\n    # Calculate the new proof by using our PoW algorithm\n    last_block = myblockchain.last_block\n    last_proof = last_block['proof']\n    proof = myblockchain.pow(last_proof)\n\n    # For finding/mining the proof, the miner is granted a reward\n    # The sender is nobody, as this coin is coming out of the void\n    myblockchain.create_new_transaction(\n        sender=\"0\",\n        recipient=node_identifier,\n        amount=1,\n    )\n\n    # Add the new created block to the chain\n    previous_hash = myblockchain.hash(last_block)\n    newblock = myblockchain.create_new_block(proof, previous_hash)\n\n    output = {\n        'message': \"A new block was mined\",\n        'index': newblock['index'],\n        'transactions': newblock['transactions'],\n        'proof': newblock['proof'],\n        'previous_hash': newblock['previous_hash'],\n    }\n    return jsonify(output), 200\n```\n# Hello World!\nNow, **finally** we will be interacting with our blockchain API. Grab your HTTP client of choice and get going! I will explain the procedure for Postman and cURL.\n## Step 12: Start up the chain\nFirst off fire up your server. \nIn PyCharm simply click on _Run_ -> _Run..._ and select _[your filename].py_ as the file to run, in my case _myblockchain.py_.\nIf you chose to use a simple python file without an IDE, fire up a terminal or command prompt window inside the directory your file is located in and execute the following command\n```\npython blockchain.py\n```\nas a result you will see something similar to this\n```\n$ python blockchain.py\n* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)\n```\n**Note that you may be prompted with a dialogue of your firewall. Just accept it.**\n## Step 13: Mining it all!\nOk let's try the most exciting thing first, **mining**. I'm sure you can't wait to mine your first block, so let's do it!\nAs you can see in the code\n```python\n[...]\[email protected]('/mining', methods=['GET'])\ndef mining():\n    [...]\n```\nwe will be interacting with the `mining` part of our API through `GET` requests. This makes sense, as our only goal with this part of the API is, to mine a new block. We don't have to pass anything to the function at all, so a `GET` request is the way to go.\n### Postman\nIf you chose to use Postman, here is a quick tutorial on how to make a post request. \n1. First you have to register for an account, if you haven't already done that\n2. and login after that. \n3. If you are logged in, you shoudl be provided with several options such as _Request_, _Collection_, _Environment_.\n4. You could simply use the option _Request_, but to keep things organized, we are going to select the _Collection_ option. \n5. After that simply choose a name for your collection, in my case I'm using _MyBlockChain_ as my name.\n6. Now click on the _New_ Button, located in the top left corner and select _Request_ this time. We are now going to be creating 3 requests.\n7. The first request is going to be our _mining_ request, second is a _new transaction_ request and finally we will have a _get whole blockchain_ request. Of course you can customize the request names as you like. \n8. **Make sure, as you create these 3 requests, that you select our newly created Collection in the bottom section of the dialogue!**\n9. Now click on our Collection's folder in the left sidebar. You should see your 3 newly created requests. Select the _mining_ request first.\n10. On the right you are now provided with an interface. As you can see by the selected item from the dropdown box, left to the text field, a `GET` request is the standard request type, so we don't have to change that yet. \n11. In the text field `Enter request URL` we are now going to enter the `mining` URL of our API, so enter `http://localhost:5000/mining` as the request URL.\n### cURL\nIf you chose to use cURL as your HTTP client, simply type `curl -i -H \"Content-Type: application/json\" -X GET http://localhost:5000/mining` in a terminal window\n### Either way\nWith both methods you should see something similar to this as a result\n```json\n{\n    \"index\": 2,\n    \"message\": \"New Block Forged\",\n    \"previous_hash\": \"0f9cb2f06100899cb31b85fef221e243d1088c0aa6840a568e58d4a27dbd186a\",\n    \"proof\": 888273,\n    \"transactions\": [\n        {\n            \"amount\": 1,\n            \"recipient\": \"491002ea048a42609d967027cc46a07b\",\n            \"sender\": \"0\"\n        }\n    ]\n}\n```\n## Step 14: Transactions are great!\nAs our mining algorithm seems to be working fine, let's create a new transaction, to be stored in a fresh mined block. To do that in\n### Postman\n1. Click on the _new transaction_ request in the left sidebar.\n2. Click on the _GET_ button with the small arrow pointing down.\n3. Select _POST_ from the drop-down list.\n4. In the navbar below the text field, select _Body_ \n5. and then mark the _raw_ option.\n6. You should now be provided with an editor like text area, and another drop-down menu next to the _binary_ option, where _Text_ is currently selected. Select _JSON (application/json)_ from this list.\n7. Now type in the following into the text area.\n```json\n{\n \"sender\": \"your-node-address\",\n \"recipient\": \"another-node-address\",\n \"amount\": 212\n}\n```\n### cURL\nJust execute `curl -X POST -H \"Content-Type: application/json\" -d '{\"sender\": \"your-node-address\", \"recipient\": \"another-node-address\", \"amount\": 212}' \"http://localhost:5000/transactions/add\"` in a terminal window.\n### In both cases\nReplace `your-node-address` with the _recipient_ address from you mining request, as this is your node address. You can also select any other 32 digit hexadezimal number, for now. Furthermore replace `another-node-address` with a random 32 digit hexadezimal number for now, as we currently don't have any other nodes.\nAdjust the `amount` to your liking.\nAnd **voilà**! You have registered your first transaction!\n## Step 15: The Chain...\nSo let's inspect our chain! If you're using\n### Postman\nClick on the _get whole blockchain_ request in the left sidebar and simply enter `http://localhost:5000/blockchain` in the `Enter request URL` text field, as _GET_ should be preselected. If not, please change it to the _GET_ option.\n### cURL\njust execute  `curl -i -H \"Content-Type: application/json\" -X GET http://localhost:5000/blockchain` in a terminal window.\n### Either way\nyou should get your whole blockchain in form of a JSON-Object. In my case, my blockchain looks like this, after mining 2 times, adding 3 transactions and mining another block:\n```json\n{\n    \"chain\": [\n        {\n            \"index\": 1,\n            \"previous_hash\": \"1\",\n            \"proof\": 100,\n            \"timestamp\": 1515156902.4502413,\n            \"transactions\": []\n        },\n        {\n            \"index\": 2,\n            \"previous_hash\": \"0f9cb2f06100899cb31b85fef221e243d1088c0aa6840a568e58d4a27dbd186a\",\n            \"proof\": 888273,\n            \"timestamp\": 1515156913.2686973,\n            \"transactions\": [\n                {\n                    \"amount\": 1,\n                    \"recipient\": \"491002ea048a42609d967027cc46a07b\",\n                    \"sender\": \"0\"\n                }\n            ]\n        },\n        {\n            \"index\": 3,\n            \"previous_hash\": \"1d2ae4a41f4a82ce6f04944e8227bf9c4d951d560f8763b910d7314634dfe09c\",\n            \"proof\": 1156297,\n            \"timestamp\": 1515158367.3596537,\n            \"transactions\": [\n                {\n                    \"amount\": 212,\n                    \"recipient\": \"d4ee26eee15148ee92c6cd394edd974e\",\n                    \"sender\": \"491002ea048a42609d967027cc46a07b\"\n                },\n                {\n                    \"amount\": 212,\n                    \"recipient\": \"5654c5654e1b551a65e15f5e4651c156\",\n                    \"sender\": \"491002ea048a42609d967027cc46a07b\"\n                },\n                {\n                    \"amount\": 111,\n                    \"recipient\": \"491002ea048a42609d967027cc46a07b\",\n                    \"sender\": \"5654c5654e1b551a65e15f5e4651c156\"\n                },\n                {\n                    \"amount\": 1,\n                    \"recipient\": \"491002ea048a42609d967027cc46a07b\",\n                    \"sender\": \"0\"\n                }\n            ]\n        }\n    ],\n    \"length\": 3\n}\n```\n# Decentralizing it\nOk, so we got a blockchain, that's working fine and we can interact with it. But one very important thing is still missing: **Decentralization**. \nThis is a core element of the blockchain idea. \nFirst off by decentralizing the whole thing, safety and integrity of the blockchain is guaranteed, as a change in the blockchain will be recognized, by the other nodes, as they also have a copy of the blockchain, and discarded. \nThe second reason is that we somehow have to make sense of our transactions. For this we need other nodes and why shouldn't they contribute to our network, by being a part of the blockchain system?! \nBut we still have a conflict there: What if a node has a blockchain that differs from all the others? \nFor our simple blockchain we will always make the **longest valid** blockchain authorative.\n## Step 16: Someone out there?!\nBut first things first. \nTo get started, we first have to implement other nodes into our system.\nTo accomplish this task, we have to adjust a few things in our API. First off, we are going to implement some new endpoints:\n1. `/nodes/add` to add new nodes in form of a list of URLs\n2. `/nodes/resolve` to resolve the conflict we discussed previously by using a consensus algorithm.\nTo do this, we have to modify our Blockchain class first:\n```python\n[...]\nfrom urllib.parse import urlparse\n\nclass MyBlockChain(object):\n    def __init__(self):\n        [...]\n        self.nodes = set()\n\n    def add_node(self, address):\n        \"\"\"\n        Register a new node\n        :param address: <str> This is the new node's address, for example 'http://192.168.1.112:5000'\n        :return: None\n        \"\"\"\n\n        node_url = urlparse(address)\n        self.nodes.add(node_url.netloc)\n```\n## Step 17: We need Consensus\nTo resolve the conflict of differing blockchains between the nodes, we are going to implement a consensus algorithm. As we discussed earlier, we are always utilizing the longest valid blockchain.\nFirst we are implementing a function that validates a blockchain:\n```python\n[...]\nimport requests\n\nclass MyBlockChain(object)\n    [...]\n    \n    def validate_blockchain(self, test_chain):\n        \"\"\"\n        Evaluate, whether a blockchain is valid\n        :param chain: <list> The blockchain that shall be tested\n        :return: <bool> Returns true if the blockchain is valid\n        \"\"\"\n\n        last_block = test_chain[0]\n        current_index = 1\n\n        while current_index < len(test_chain):\n            block = test_chain[current_index]\n            \n            # Determine, whether the hash is correct\n            if block['previous_hash'] != self.hash(last_block):\n                return False\n\n            # Determine, wheter the proof of work is correct\n            if not self.validate_proof(last_block['proof'], block['proof']):\n                return False\n\n            last_block = block\n            current_index += 1\n\n        return True\n```\nNow we just have to run every blockchain in our surrounding network through this consensus algorithm:\n```python\n [...]\n\nclass MyBlockChain(object)\n    [...]\n    def resolve(self):\n        \"\"\"\n        This algorithm resolves conflicts between our nodes. It is the consensus algorithm which I mentioned previously.\n        :return: <bool> Returns true, if our chain was substituted with an updated version\n        \"\"\"\n\n        surrounding_nodes = self.nodes\n        updated_chain = None\n\n        # If we follow our consensus algorithm description, we only want blockchains that are longer, than our current chain\n        max_length = len(self.blockchain)\n\n        # Iterate every surrounding nodes in our network through the consensus algorithm, which means checking if the node's blockchain is longer than our current blockchain and valid and set it as our new blockchain and continue checking, as there could be an even longer and valid blockchain.\n        for node_iterator in surrounding_nodes:\n            response = requests.get(f'http://{node_iterator}/blockchain')\n\n            if response.status_code == 200:\n                length = response.json()['length']\n                chain_iterator = response.json()['chain']\n\n                if length > max_length and self.validate_blockchain(chain_iterator):\n                    max_length = length\n                    updated_chain = chain_iterator\n\n        # If we found a new blockchain, replace our current blockchain with the new one\n        if updated_chain:\n            self.blockchain = updated_chain\n            return True\n\n        return False\n```\nNow we just have to register our new functions as new endpoints in the API:\n```python\[email protected]('/nodes/add', methods=['POST'])\ndef add_nodes():\n    values = request.get_json()\n\n    nodes = values.get('nodes')\n    if nodes is None:\n        return \"You didn't post a valid list of nodes. Please double check your input!\", 400\n\n    for node in nodes:\n        myblockchain.add_node(node)\n\n    response = {\n        'message': 'All of your specified nodes have been added to the network!',\n        'total_nodes': list(myblockchain.nodes),\n    }\n    return jsonify(response), 201\n\n\[email protected]('/nodes/resolve', methods=['GET'])\ndef consensus():\n    replaced = myblockchain.resolve()\n\n    if replaced:\n        response = {\n            'message': 'There was a longer valid chain within the network. The blockchain of this node has been replaced.',\n            'new_chain': myblockchain.blockchain\n        }\n    else:\n        response = {\n            'message': 'The blockchain of this node is already the longest valid chain within the network.',\n            'chain': myblockchain.blockchain\n        }\n\n    return jsonify(response), 200\n```\n## Step 18: Friends are great. Even if they're virtual...\nTo test our decentralization algorithms, either grab some friends, to run some nodes for you, or just run the same program on different ports, so you would have to start up an instance of our blockchain-program, then change to port to 5001 for example, save, fire up an instance of this _modified_ program, change the port to 5002, etc. \n## Step 19: Add them to your friends list\nIf you got some instances, you just have to register them. To do this, simply send a `POST` request with the following content\n```json\n{\n    \"nodes\": [\"http://[ip-of-another-node-or-127.0.0.1-for-your-local-machine]:[the-port-number]\"]\n}\n```\nto `http://[the-node-ip-you-want-to-register-it-to]:[port]/nodes/add`\n## Step 20: Consensus check\nAfter that try to mine some blocks and even add some transactions on let's say node 2 and then run `http://[a-node-ip]:[port]/nodes/resolve` on let's say node 1. The consensus algorithm should step into action and update the blockchain of node 1.\n# The whole thang\nI keep my promises\n```python\nimport hashlib\nimport json\nimport requests\nfrom time import time\nfrom uuid import uuid4\nfrom textwrap import dedent\nfrom flask import Flask, jsonify, request\nfrom urllib.parse import urlparse\n\nclass MyBlockChain(object):\n    def __init__(self):\n        self.blockchain = []\n        self.transactions = []\n        \n        # Creation of the mentioned genesis block\n        self.create_new_block(previous_hash=1, proof=100)\n        \n        self.nodes = set()\n        \n    def create_new_block(self, proof, previous_hash=None):\n        \"\"\"\n        Creates a new block and adds it to the blockchain\n        :param proof: <int> This is generated by the proof of work algorithm\n        :param previous_hash: (Optional) <str> Hash of the preleading Block\n        :return: <dict> Return the new block\n        \"\"\"\n\n        new_block = {\n            'index': len(self.blockchain) + 1,\n            'timestamp': time(),\n            'transactions': self.transactions,\n            'proof': proof,\n            'previous_hash': previous_hash or self.hash(self.blockchain[-1]),\n        }\n\n        # As all pending transactions have been processed and added to the block, the list can be resetted\n        self.transactions = []\n        \n        # Add the new block to the blockchain\n        self.blockchain.append(new_block)\n        return new_block\n    \n    def create_new_transaction(self, sender, recipient, amount):\n        \"\"\"\n        This function creates a new transaction that will then be placed in a new block, alone or bundled together with other transactions.\n        \n        :param sender: <str> Sender's address\n        :param recipient: <str> Recipient's address\n        :param amount: <int> Amount to be transferred\n        :return: <int> This is the index of the block that will contain this transaction\n        \"\"\"\n\n        self.transactions.append({\n            'sender': sender,\n            'recipient': recipient,\n            'amount': amount,\n        })\n\n        return self.last_block['index'] + 1\n    \n    @staticmethod\n    def hash(block):\n        \"\"\"\n        This function hashes the block using the SHA-256 hash algorithm\n        The function is given a block and returns a string, consisting of the hash\n        :param block: <dict> Block\n        :return: <str>\n        \"\"\"\n\n        # As every change in an item changes the hash, we first have to do a little sort operation, or else we would get inconsistent hashes\n        block_sorted = json.dumps(block, sort_keys=True).encode()\n        return hashlib.sha256(block_sorted).hexdigest()\n\n    @property\n    def last_block(self):\n        return self.blockchain[-1]\n        \n    def pow(self, last_proof):\n        \"\"\"\n        Simple PoW Algorithm:\n         - Find a number y, so that hash(xy) starts with 5 zeroes. x is the last y aka last_proof. y is then the new proof.\n        :param last_proof: <int>\n        :return: <int>\n        \"\"\"\n        \n        current_proof = 0\n        while self.validate_proof(last_proof, current_proof) is False:\n            current_proof += 1\n\n        return current_proof\n\n    @staticmethod\n    def validate_proof(last_proof, current_proof):\n        \"\"\"\n        Returns, whether the hash of the lastproof and the current_proof contains 5 leading zeroes.\n        :param last_proof: <int> Previous Proof Number\n        :param current_proof: <int> Current Proof Number\n        :return: <bool>\n        \"\"\"\n\n        possible_hash = hashlib.sha256(f'{last_proof}{current_proof}'.encode()).hexdigest()\n        return possible_hash[:5] == \"00000\"\n        \n    def add_node(self, address):\n        \"\"\"\n        Register a new node\n        :param address: <str> This is the new node's address, for example 'http://192.168.1.112:5000'\n        :return: None\n        \"\"\"\n\n        node_url = urlparse(address)\n        self.nodes.add(node_url.netloc)\n        \n    def validate_blockchain(self, test_chain):\n        \"\"\"\n        Evaluate, whether a blockchain is valid\n        :param chain: <list> The blockchain that shall be tested\n        :return: <bool> Returns true if the blockchain is valid\n        \"\"\"\n\n        last_block = test_chain[0]\n        current_index = 1\n\n        while current_index < len(test_chain):\n            block = test_chain[current_index]\n            \n            # Determine, whether the hash is correct\n            if block['previous_hash'] != self.hash(last_block):\n                return False\n\n            # Determine, wheter the proof of work is correct\n            if not self.validate_proof(last_block['proof'], block['proof']):\n                return False\n\n            last_block = block\n            current_index += 1\n\n        return True\n        \n    def resolve(self):\n        \"\"\"\n        This algorithm resolves conflicts between our nodes. It is the consensus algorithm which I mentioned previously.\n        :return: <bool> Returns true, if our chain was substituted with an updated version\n        \"\"\"\n\n        surrounding_nodes = self.nodes\n        updated_chain = None\n\n        # If we follow our consensus algorithm description, we only want blockchains that are longer, than our current chain\n        max_length = len(self.blockchain)\n\n        # Iterate every surrounding nodes in our network through the consensus algorithm, which means checking if the node's blockchain is longer than our current blockchain and valid and set it as our new blockchain and continue checking, as there could be an even longer and valid blockchain.\n        for node_iterator in surrounding_nodes:\n            response = requests.get(f'http://{node_iterator}/blockchain')\n\n            if response.status_code == 200:\n                length = response.json()['length']\n                chain_iterator = response.json()['chain']\n\n                if length > max_length and self.validate_blockchain(chain_iterator):\n                    max_length = length\n                    updated_chain = chain_iterator\n\n        # If we found a new blockchain, replace our current blockchain with the new one\n        if updated_chain:\n            self.blockchain = updated_chain\n            return True\n\n        return False\n\napp = Flask(__name__)\nnode_identifier = str(uuid4()).replace('-', '')\n\nmyblockchain = MyBlockChain()\n\[email protected]('/blockchain', methods=['GET'])\ndef get_full_chain():\n    output = {\n        'chain': myblockchain.blockchain,\n        'length': len(myblockchain.blockchain),\n    }\n    return jsonify(output), 200\n\[email protected]('/mining', methods=['GET'])\ndef mining():\n    # Calculate the new proof by using our PoW algorithm\n    last_block = myblockchain.last_block\n    last_proof = last_block['proof']\n    proof = myblockchain.pow(last_proof)\n\n    # For finding/mining the proof, the miner is granted a reward\n    # The sender is nobody, as this coin is coming out of the void\n    myblockchain.create_new_transaction(\n        sender=\"0\",\n        recipient=node_identifier,\n        amount=1,\n    )\n\n    # Add the new created block to the chain\n    previous_hash = myblockchain.hash(last_block)\n    newblock = myblockchain.create_new_block(proof, previous_hash)\n\n    output = {\n        'message': \"A new block was mined\",\n        'index': newblock['index'],\n        'transactions': newblock['transactions'],\n        'proof': newblock['proof'],\n        'previous_hash': newblock['previous_hash'],\n    }\n    return jsonify(output), 200\n    \[email protected]('/transactions/add', methods=['POST'])\ndef add_transaction():\n    values = request.get_json()\n\n    # The POST request has to have the following required fields\n    required = ['sender', 'recipient', 'amount']\n    if not all(k in values for k in required):\n        return 'There are values missing', 400\n\n    # Adds a new transaction by utilizing our function\n    index = myblockchain.create_new_transaction(values['sender'], values['recipient'], values['amount'])\n\n    output = {'message': f'Your registered Transaction is going to be a part of the block with the index of {index}'}\n    return jsonify(output), 201\n    \[email protected]('/nodes/add', methods=['POST'])\ndef add_nodes():\n    values = request.get_json()\n\n    nodes = values.get('nodes')\n    if nodes is None:\n        return \"You didn't post a valid list of nodes. Please double check your input!\", 400\n\n    for node in nodes:\n        myblockchain.add_node(node)\n\n    response = {\n        'message': 'All of your specified nodes have been added to the network!',\n        'total_nodes': list(myblockchain.nodes),\n    }\n    return jsonify(response), 201\n\n\[email protected]('/nodes/resolve', methods=['GET'])\ndef consensus():\n    replaced = myblockchain.resolve()\n\n    if replaced:\n        response = {\n            'message': 'There was a longer valid chain within the network. The blockchain of this node has been replaced.',\n            'new_chain': myblockchain.blockchain\n        }\n    else:\n        response = {\n            'message': 'The blockchain of this node is already the longest valid chain within the network.',\n            'chain': myblockchain.blockchain\n        }\n\n    return jsonify(response), 200\n\nif __name__ == '__main__':\n    app.run(host='0.0.0.0', port=5000)\n```\n# Final thoughts\nAnd there you have it!\nYour very own blockchain. Wasn't very hard, was it?\nI sincerely hope you had fun thorughout this tutorial and were able to understand the concept and system behind it better. If you have any questions, please ask them in the comments and I'll try my best to answer them.\n# The obligatory begging\nAs this whole tutorial took me over 2 days to finish, I would love to see a lot of comments and feedback under this post. Also if you find any typos, grammar mistakes, etc. and care to tell me, i would be mor than happy about it, as English is not my native language. So please excuse any mistakes I made. I tried my very best.\nOf course please upvote, if you worship my effort to enrich the community, and if you want to see more such content, consider following me. \nI wish you only the best - See ya!",
      "json_metadata": "{\"tags\":[\"steemit\",\"blockchain\",\"trevonjb\",\"cryptocurrency\",\"craigrant\"],\"links\":[\"https://www.python.org/downloads/windows/\",\"https://en.wikipedia.org/wiki/Integrated_development_environment\",\"https://www.jetbrains.com/pycharm\",\"https://www.getpostman.com/\",\"https://curl.haxx.se/\",\"https://en.wikipedia.org/wiki/SHA-2\",\"https://en.wikipedia.org/wiki/Proof-of-work_system\"],\"app\":\"steemit/0.1\",\"format\":\"markdown\"}",
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      "permlink": "create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required",
      "title": "Create your own blockchain & cryptocurrency! - understand blockchains by creating one in python - no knowledge required"
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  "timestamp": "2018-01-06T14:08:54",
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dustvoicepublished a new post: create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 14:07:54 UTC

18,742,267|0db3d51

author	dustvoice
body	# What exactly is a blockchain? - How does a blockchain work? - What is Bitcoin or STEEM exactly? - How does a blockchain make sure of its correctness - What is mining exactly? These are only some questions, probably many of you are asking yourselves. I'm here to provide you with kind of an unusual answer. My goal is to help you undestand the whole system behind blockchains, by actually creating a small blockchain yourself! With the rise of cryptocurrencies and decentralized systems like Bitcoin or STEEM, many people want to really undestand, what this is all about. I will show you how the system works, by coding a blockchain from scratch in python with you. The guide will be mainly for Windows, but I will also add comments regarding Linux. You don't know a whole of python, to follow this guide, but it is advised to know the most basic basics. # Get ready ## Setup Python and pip First off, we need to install Python 3.6+ along with pip, with which you can install python packages. - On Linux, you can install python, by simply typing `sudo apt-get install python3.6` into the terminal. If you encounter errors, please try `sudo apt-get update` and then try to execute the command again. If it still doesn't work, please search for installation instructions for your specific system on your preferred search engine. - On Windows, 1. first download the binary, that suits your system best, under the [official python download page for windows.](https://www.python.org/downloads/windows/). Make sure you grab at least the _version 3.6_ or higher. 2. Install the file you just downloaded. Make sure you check the option to install pip, when provided with an option to do so. If not, don't worry, it probably is enabled by default. ## IDE or not? As a next step, you want to decide, whether to utilize an [IDE](https://en.wikipedia.org/wiki/Integrated_development_environment) or not. An IDE is an environment, which supports you in the creation process of your application, by providing many features, with for example syntax highlighting, or code completion, to name just 2 possible features. My favorite IDE for Python development is probably PyCharm, which you can fetch from [this link.](https://www.jetbrains.com/pycharm) Setting up PyCharm on Windows is as simple, as downloading the executable installer and installing it with the provided setup utility. PyCharm is free tu use, as long as you use the Community Edition. You can also use your coding notepad of choice. We will only work in one file, which you have to execute, so as long as your text-editing software is able to produce files with the ending `.py`, it will work fine. ## Setup your workspace (PyCharm) If you decided to use PyCharm, simply open it up and click on _Create Project_ in the popup dialogue. In the next dialogue you want to specify your project's name. I chose to use _MyBlockChain_ as my project name. Finally click on _create_ in the bottom right corner. On your left hand side, you're now provided with a file tree. 1. Right-Click on the folder which consists of your project's name, in my case _MyBlockChain_ 2. Go to _new_ 3. Finally click on _Python File_ and 4. Define a Filename. I chose `MyBlockChain.py` as my filename. ## Create your file (Simple Text Editor) If you use a simple text editor, just create a file anywhere you like with the file extension `.py`. In my case I chose to use the filename `MyBlockChain.py`. ## Install the needed packages ### PyCharm In PyCharm you can install packages very easily and add them to your project: 1. Make sure, you have your project open 2. Go to _File_ -> _Settings_ -> _Project: [your project name]_ -> _Project Interpreter_ 3. Then click on the green plus symbol. 4. In the search field type in _Flask_ first. Select the first entry, which simply says _Flask_. Then click on Install Package in the bottom left corner. 5. Do the same thing for _Requests_. ### Pip If you chose not to use PyCharm, you simply need to open up the terminal on linux or the command prompt, or PowerShell on Windows _(simply press Windows+R and type in cmd)_ and then execute `pip install Flask==0.12.2 requests==2.18.4 `. If this gives you an error, please double check that you have _pip_ installed. If the problem still occurs, please troubleshoot the error message using google, as there are too many possibilities, what the error could be caused by, for me to discuss every one of them here. ## Getting a HTTP-Client You will also need a HTTP-Client, as we need to make `GET` and `POST` requests to our Flask instance, at some Point in time. Mainly, there are two options - [_Postman_](https://www.getpostman.com/) or [_cURL_](https://curl.haxx.se/). I highly recommend _Postman_, as it is easy and intuitive to use, but if you just want a simple and quick solution, without having to register for an account, just use _cURL_. Online solutions, probably won't work, as the webserver you are going to be trying to access, is just on your local machine. ## Just gimme the source code! If you just want the source code and don't want to follow my instructions, please scroll down, to the very end of this post, where I will add the source code in its complete beauty. # The Blockchain - Your Blockchain ## Step 1: Creating a simplistic Blockchain A block chain is basically a chain of blocks that are linked together in some way, as you have already figured. In this case, every block contains a hash of the previous block. A hash is a hexadecimal number that is determined by a specific algorithm. Imagine a hash being a digital fingerprint of an item. A good hash algorithm will never return the same hash for two different items, so every hash is individual. In our case we will be using the [_SHA-256_](https://en.wikipedia.org/wiki/SHA-2) algorithm. Furthermore the hash algorithm is not reversible, so you can't determine the object, by having its hash, but you can always apply the hash algorithm on the object, to get its hash. As every item has the hash of its previous item, the blockchain is protected against violation, as one would have to change every following block, as the hash changes with every change, as two different items can't have the same hash. ### The Blockchain class Our Blockchain class basically consists of a constructor and some functions. In the constructor, we will create two empty lists - one to store our blockchain in and another, for our transactions. As for now, our class will have several functions: - A function to create new blocks - A function to create new transactions - A function, which hashes a block - A function to fetch the last block The python template looks like this: ```python class MyBlockChain(object): def __init__(self): self.blockchain = [] self.transactions = [] def create_new_block(self): # This function creates a new block and appends it to the chain pass def create_new_transaction(self): # This function creates a new transaction and adds it to the list of transactions pass @staticmethod def hash(block): # This method hashes the passed block pass @property def last_block(self): # This function returns the last block in the chain pass ``` ## Step 2: The blocks As described earlier, a blockchain consists of blocks. So I will cover them first. Each Block has 5 fields: - An index, - an Unix timestamp, - a list of transactions, - a proof, - and finally the hash of the previous block. Just to clarify things, here is an example of a block ```json example_block = { 'index': 5, 'timestamp': 1515110045.123456, 'transactions': [ { 'sender': "154d8554f9541e12354e1234f512a001", 'recipient': "8654e21254c6512a51bce156542d1e5c", 'amount': 212, } ], 'proof': 488612354568, 'previous_hash': "c7be1ed902fb8dd4d48997c6452f5d7e509fbcdbe2808b16bcf4edce4c07d14e" } ``` ## Step 3: Hashing it As every block needs the hash of the previous block, we need a function, that calculates the hash of a block. To accomplish this, we simply modify our empty `hash` function ```python import hashlib import json class MyBlockChain(object): [...] @staticmethod def hash(block): """ This function hashes the block using the SHA-256 hash algorithm The function is given a block and returns a string, consisting of the hash :param block: <dict> Block :return: <str> """ # As every change in an item changes the hash, we first have to do a little sort operation, or else we would get inconsistent hashes block_sorted = json.dumps(block, sort_keys=True).encode() return hashlib.sha256(block_sorted).hexdigest() ``` ## Step 4: Transactions Our `create_new_transaction` method is responsible for adding new transactions to the `transactions` list, which will then be stored inside a block. The whole function is pretty self explanatory. But first we need a function to return the last block of the chain, as we will calculate the new index, at which the transaction will be stored, by increasing the index of the last block by 1 ```python class MyBlockChain(object): [...] @property def last_block(self): return self.blockchain[-1] ``` Now we can fill out the `create_new_transaction` function ```python class MyBlockChain(object): [...] def create_new_transaction(self, sender, recipient, amount): """ This function creates a new transaction that will then be placed in a new block, alone or bundled together with other transactions. :param sender: <str> Sender's address :param recipient: <str> Recipient's address :param amount: <int> Amount to be transferred :return: <int> This is the index of the block that will contain this transaction """ self.transactions.append({ 'sender': sender, 'recipient': recipient, 'amount': amount, }) return self.last_block['index'] + 1 ``` ## Step 5: Creating new Blocks By now we almost have everything at our hands, what we need in order to make a new block. The only thing missing is the _proof_ field. As this is a little harder to understand, I will explain it later. But we still have one problem - if every block has the hash of the previous block, what shall we do with our first block, as there is no previous block for us to hash. This first block is called the _genesis_ block. ```python import hashlib import json from time import time class MyBlockChain(object): def __init__(self): self.blockchain = [] self.transactions = [] # Creation of the mentioned genesis block self.create_new_block(previous_hash=1, proof=100) def create_new_block(self, proof, previous_hash=None): """ Creates a new block and adds it to the blockchain :param proof: <int> This is generated by the proof of work algorithm :param previous_hash: (Optional) <str> Hash of the preleading Block :return: <dict> Return the new block """ new_block = { 'index': len(self.blockchain) + 1, 'timestamp': time(), 'transactions': self.transactions, 'proof': proof, 'previous_hash': previous_hash or self.hash(self.blockchain[-1]), } # As all pending transactions have been processed and added to the block, the list can be resetted self.transactions = [] # Add the new block to the blockchain self.blockchain.append(new_block) return new_block ``` ## Step 6: What's up with the proof?! ### The [Proof of Work (PoW) algorithm](https://en.wikipedia.org/wiki/Proof-of-work_system) This system wants to proof that work has been done. Now a little bit less abstract. Basically we are searching for a number that matches a specific criteria. The thing is, for the system to work, the process of finding a number matching the criteria has to be difficult, but the verification process has to be quick and easy. This is how new blocks are created, or expressed in another, more commonly used term, _mined_. #### Still too abstract? Ok here is an example: We are looking for a hash of a product of two integers that ends with a 1. So the result of the multiplication of `a` and `b` gets hashed and has to end with a 1. If we set a to `a` static value, our algorithm will determine a value for `b`, for which this criteria is matched. ```python from hashlib import sha256 a = 12 b = 0 # We don't know what b has to be. It will be determined by the algorithm while sha256(f'{ab}'.encode()).hexdigest()[-1] != "1": b += 1 print(f'The solution is b = {b}') ``` This example outputs ``` The solution is b = 4 ``` This means that the hash of `124` ends with a 1 ``` hash(48) = 98010bd9270f9b100b6214a21754fd33bdc8d41b2bc9f9dd16ff54d3c34ffd71 ``` As you can tell, the verification process doesn't need countless loops, until it finds a matching pair. You just have to run the hash algorithm once on the numbers and you can easily determine, whether the numbers match the criteria, or not. ## Step 7: Implementing PoW Firstoff, we need a criteria, or commonly referred to as a rule. For now, our rule is that the hash has to have 5 leading zeroes, so `000005bc845e...` would be a valid result, but `000019ea76c4` would not. As the difficulty rises extremely, if we would require 6 leading zeros, the difficulty of our simple algorithm can be adjusted by changing the amount of leading zeroes required. This is the implementation in python: ```python [...] from uuid import uuid4 class MyBlockChain(object): [...] def pow(self, last_proof): """ Simple PoW Algorithm: - Find a number y, so that hash(xy) starts with 5 zeroes. x is the last y aka last_proof. y is then the new proof. :param last_proof: <int> :return: <int> """ current_proof = 0 while self.validate_proof(last_proof, current_proof) is False: current_proof += 1 return current_proof @staticmethod def validate_proof(last_proof, current_proof): """ Returns, whether the hash of the lastproof and the current_proof contains 5 leading zeroes. :param last_proof: <int> Previous Proof Number :param current_proof: <int> Current Proof Number :return: <bool> """ possible_hash = hashlib.sha256(f'{last_proof}{current_proof}'.encode()).hexdigest() return possible_hash[:5] == "00000" ``` ## Step 8: Interacting with our class Now we are able to create a blockchain. But we can't really interact with it, as we have only interacted with the functions and variables of our class. We are going to use HTTP requests to interact with our blockchain. So let's set it up! # HTTP in the house! To talk to our blockchain using Http requests, we need some help - which comes in the form of the _Flask Framework_. We will create and implement 3 basic methods for now: - `/blockchain` to retrieve the full blockchain - `/mining` to make our simple server mine a block - `/transactions/add` to add a new transaction to the blockchain. ## Step 9: Flask First we need to implement Flask. Here is the code: ```python [...] from textwrap import dedent from flask import Flask, jsonify, request class MyBlockChain(object): [...] app = Flask(__name__) node_identifier = str(uuid4()).replace('-', '') myblockchain = MyBlockChain() @app.route('/blockchain', methods=['GET']) def get_full_chain(): output = { 'chain': myblockchain.blockchain, 'length': len(myblockchain.blockchain), } return jsonify(output), 200 @app.route('/mining', methods=['GET']) def mining(): pass @app.route('/transactions/add', methods=['POST']) def add_transaction(): pass if __name__ == '__main__': app.run(host='0.0.0.0', port=5000) ``` ## Step 10: Adding Transactions As this is commonly the main task of a block chain and also required for a new block, I will cover this first. The user sends a _POST request_ to `/transactions/add` with a JSON object, containing all required fields. This is an example, for a possible, valid request: ```json { "sender": "154d8554f9541e12354e1234f512a001", "recipient": "8654e21254c6512a51bce156542d1e5c", "amount": 212 } ``` As you can see, a request has three fields: - A _sender_ field, with the sender id, - a _recipient_ field, with the recipient id - and an amount, which defines how many units are to be transferred Now we just need to implement this function ```python [...] @app.route('/transactions/add', methods=['POST']) def add_transaction(): values = request.get_json() # The POST request has to have the following required fields required = ['sender', 'recipient', 'amount'] if not all(k in values for k in required): return 'There are values missing', 400 # Adds a new transaction by utilizing our function index = myblockchain.create_new_transaction(values['sender'], values['recipient'], values['amount']) output = {'message': f'Your registered Transaction is going to be a part of the block with the index of {index}'} return jsonify(output), 201 ``` This function simply calls the `create_new_transaction` method with the parameters of the POST request ## Step 11: Setup your mines As discussed earlier, future blocks have to be mined. If a new block is found/mined, all pending transactions are added to this block. To 'mine' a new block, our function hast to do three things 1. Calculate the proof 2. Reward the miner with a specific amount of coins (in our example 1 coin) 3. Add the new mined block to the blockchain _(The fact that the recipient is our current node, will make more sense, as we will talk about decentralization later on.)_ ```python @app.route('/mining', methods=['GET']) def mining(): # Calculate the new proof by using our PoW algorithm last_block = myblockchain.last_block last_proof = last_block['proof'] proof = myblockchain.pow(last_proof) # For finding/mining the proof, the miner is granted a reward # The sender is nobody, as this coin is coming out of the void myblockchain.create_new_transaction( sender="0", recipient=node_identifier, amount=1, ) # Add the new created block to the chain previous_hash = myblockchain.hash(last_block) newblock = myblockchain.create_new_block(proof, previous_hash) output = { 'message': "A new block was mined", 'index': newblock['index'], 'transactions': newblock['transactions'], 'proof': newblock['proof'], 'previous_hash': newblock['previous_hash'], } return jsonify(output), 200 ``` # Hello World! Now, finally we will be interacting with our blockchain API. Grab your HTTP client of choice and get going! I will explain the procedure for Postman and cURL. ## Step 12: Start up the chain First off fire up your server. In PyCharm simply click on _Run_ -> _Run..._ and select _[your filename].py_ as the file to run, in my case _myblockchain.py_. If you chose to use a simple python file without an IDE, fire up a terminal or command prompt window inside the directory your file is located in and execute the following command ``` python blockchain.py ``` as a result you will see something similar to this ``` $ python blockchain.py * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit) ``` Note that you may be prompted with a dialogue of your firewall. Just accept it. ## Step 13: Mining it all! Ok let's try the most exciting thing first, mining. I'm sure you can't wait to mine your first block, so let's do it! As you can see in the code ```python [...] @app.route('/mining', methods=['GET']) def mining(): [...] ``` we will be interacting with the `mining` part of our API through `GET` requests. This makes sense, as our only goal with this part of the API is, to mine a new block. We don't have to pass anything to the function at all, so a `GET` request is the way to go. ### Postman If you chose to use Postman, here is a quick tutorial on how to make a post request. 1. First you have to register for an account, if you haven't already done that 2. and login after that. 3. If you are logged in, you shoudl be provided with several options such as _Request_, _Collection_, _Environment_. 4. You could simply use the option _Request_, but to keep things organized, we are going to select the _Collection_ option. 5. After that simply choose a name for your collection, in my case I'm using _MyBlockChain_ as my name. 6. Now click on the _New_ Button, located in the top left corner and select _Request_ this time. We are now going to be creating 3 requests. 7. The first request is going to be our _mining_ request, second is a _new transaction_ request and finally we will have a _get whole blockchain_ request. Of course you can customize the request names as you like. 8. Make sure, as you create these 3 requests, that you select our newly created Collection in the bottom section of the dialogue! 9. Now click on our Collection's folder in the left sidebar. You should see your 3 newly created requests. Select the _mining_ request first. 10. On the right you are now provided with an interface. As you can see by the selected item from the dropdown box, left to the text field, a `GET` request is the standard request type, so we don't have to change that yet. 11. In the text field `Enter request URL` we are now going to enter the `mining` URL of our API, so enter `http://localhost:5000/mining` as the request URL. ### cURL If you chose to use cURL as your HTTP client, simply type `curl -i -H "Content-Type: application/json" -X GET http://localhost:5000/mining` in a terminal window ### Either way With both methods you should see something similar to this as a result ```json { "index": 2, "message": "New Block Forged", "previous_hash": "0f9cb2f06100899cb31b85fef221e243d1088c0aa6840a568e58d4a27dbd186a", "proof": 888273, "transactions": [ { "amount": 1, "recipient": "491002ea048a42609d967027cc46a07b", "sender": "0" } ] } ``` ## Step 14: Transactions are great! As our mining algorithm seems to be working fine, let's create a new transaction, to be stored in a fresh mined block. To do that in ### Postman 1. Click on the _new transaction_ request in the left sidebar. 2. Click on the _GET_ button with the small arrow pointing down. 3. Select _POST_ from the drop-down list. 4. In the navbar below the text field, select _Body_ 5. and then mark the _raw_ option. 6. You should now be provided with an editor like text area, and another drop-down menu next to the _binary_ option, where _Text_ is currently selected. Select _JSON (application/json)_ from this list. 7. Now type in the following into the text area. ```json { "sender": "your-node-address", "recipient": "another-node-address", "amount": 212 } ``` ### cURL Just execute `curl -X POST -H "Content-Type: application/json" -d '{"sender": "your-node-address", "recipient": "another-node-address", "amount": 212}' "http://localhost:5000/transactions/add"` in a terminal window. ### In both cases Replace `your-node-address` with the _recipient_ address from you mining request, as this is your node address. You can also select any other 32 digit hexadezimal number, for now. Furthermore replace `another-node-address` with a random 32 digit hexadezimal number for now, as we currently don't have any other nodes. Adjust the `amount` to your liking. And voilà! You have registered your first transaction! ## Step 15: The Chain... So let's inspect our chain! If you're using ### Postman Click on the _get whole blockchain_ request in the left sidebar and simply enter `http://localhost:5000/blockchain` in the `Enter request URL` text field, as _GET_ should be preselected. If not, please change it to the _GET_ option. ### cURL just execute `curl -i -H "Content-Type: application/json" -X GET http://localhost:5000/blockchain` in a terminal window. ### Either way you should get your whole blockchain in form of a JSON-Object. In my case, my blockchain looks like this, after mining 2 times, adding 3 transactions and mining another block: ```json { "chain": [ { "index": 1, "previous_hash": "1", "proof": 100, "timestamp": 1515156902.4502413, "transactions": [] }, { "index": 2, "previous_hash": "0f9cb2f06100899cb31b85fef221e243d1088c0aa6840a568e58d4a27dbd186a", "proof": 888273, "timestamp": 1515156913.2686973, "transactions": [ { "amount": 1, "recipient": "491002ea048a42609d967027cc46a07b", "sender": "0" } ] }, { "index": 3, "previous_hash": "1d2ae4a41f4a82ce6f04944e8227bf9c4d951d560f8763b910d7314634dfe09c", "proof": 1156297, "timestamp": 1515158367.3596537, "transactions": [ { "amount": 212, "recipient": "d4ee26eee15148ee92c6cd394edd974e", "sender": "491002ea048a42609d967027cc46a07b" }, { "amount": 212, "recipient": "5654c5654e1b551a65e15f5e4651c156", "sender": "491002ea048a42609d967027cc46a07b" }, { "amount": 111, "recipient": "491002ea048a42609d967027cc46a07b", "sender": "5654c5654e1b551a65e15f5e4651c156" }, { "amount": 1, "recipient": "491002ea048a42609d967027cc46a07b", "sender": "0" } ] } ], "length": 3 } ``` # Decentralizing it Ok, so we got a blockchain, that's working fine and we can interact with it. But one very important thing is still missing: Decentralization. This is a core element of the blockchain idea. First off by decentralizing the whole thing, safety and integrity of the blockchain is guaranteed, as a change in the blockchain will be recognized, by the other nodes, as they also have a copy of the blockchain, and discarded. The second reason is that we somehow have to make sense of our transactions. For this we need other nodes and why shouldn't they contribute to our network, by being a part of the blockchain system?! But we still have a conflict there: What if a node has a blockchain that differs from all the others? For our simple blockchain we will always make the longest valid blockchain authorative. ## Step 16: Someone out there?! But first things first. To get started, we first have to implement other nodes into our system. To accomplish this task, we have to adjust a few things in our API. First off, we are going to implement some new endpoints: 1. `/nodes/add` to add new nodes in form of a list of URLs 2. `/nodes/resolve` to resolve the conflict we discussed previously by using a consensus algorithm. To do this, we have to modify our Blockchain class first: ```python [...] from urllib.parse import urlparse class MyBlockChain(object): def __init__(self): [...] self.nodes = set() def add_node(self, address): """ Register a new node :param address: <str> This is the new node's address, for example 'http://192.168.1.112:5000' :return: None """ node_url = urlparse(address) self.nodes.add(node_url.netloc) ``` ## Step 17: We need Consensus To resolve the conflict of differing blockchains between the nodes, we are going to implement a consensus algorithm. As we discussed earlier, we are always utilizing the longest valid blockchain. First we are implementing a function that validates a blockchain: ```python [...] import requests class MyBlockChain(object) [...] def validate_blockchain(self, test_chain): """ Evaluate, whether a blockchain is valid :param chain: <list> The blockchain that shall be tested :return: <bool> Returns true if the blockchain is valid """ last_block = test_chain[0] current_index = 1 while current_index < len(test_chain): block = test_chain[current_index] # Determine, whether the hash is correct if block['previous_hash'] != self.hash(last_block): return False # Determine, wheter the proof of work is correct if not self.validate_proof(last_block['proof'], block['proof']): return False last_block = block current_index += 1 return True ``` Now we just have to run every blockchain in our surrounding network through this consensus algorithm: ```python [...] class MyBlockChain(object) [...] def resolve(self): """ This algorithm resolves conflicts between our nodes. It is the consensus algorithm which I mentioned previously. :return: <bool> Returns true, if our chain was substituted with an updated version """ surrounding_nodes = self.nodes updated_chain = None # If we follow our consensus algorithm description, we only want blockchains that are longer, than our current chain max_length = len(self.blockchain) # Iterate every surrounding nodes in our network through the consensus algorithm, which means checking if the node's blockchain is longer than our current blockchain and valid and set it as our new blockchain and continue checking, as there could be an even longer and valid blockchain. for node_iterator in surrounding_nodes: response = requests.get(f'http://{node_iterator}/blockchain') if response.status_code == 200: length = response.json()['length'] chain_iterator = response.json()['chain'] if length > max_length and self.validate_blockchain(chain_iterator): max_length = length updated_chain = chain_iterator # If we found a new blockchain, replace our current blockchain with the new one if updated_chain: self.blockchain = updated_chain return True return False ``` Now we just have to register our new functions as new endpoints in the API: ```python @app.route('/nodes/add', methods=['POST']) def add_nodes(): values = request.get_json() nodes = values.get('nodes') if nodes is None: return "You didn't post a valid list of nodes. Please double check your input!", 400 for node in nodes: myblockchain.add_node(node) response = { 'message': 'All of your specified nodes have been added to the network!', 'total_nodes': list(myblockchain.nodes), } return jsonify(response), 201 @app.route('/nodes/resolve', methods=['GET']) def consensus(): replaced = myblockchain.resolve() if replaced: response = { 'message': 'There was a longer valid chain within the network. The blockchain of this node has been replaced.', 'new_chain': myblockchain.blockchain } else: response = { 'message': 'The blockchain of this node is already the longest valid chain within the network.', 'chain': myblockchain.blockchain } return jsonify(response), 200 ``` ## Step 18: Friends are great. Even if they're virtual... To test our decentralization algorithms, either grab some friends, to run some nodes for you, or just run the same program on different ports, so you would have to start up an instance of our blockchain-program, then change to port to 5001 for example, save, fire up an instance of this _modified_ program, change the port to 5002, etc. ## Step 19: Add them to your friends list If you got some instances, you just have to register them. To do this, simply send a `POST` request with the following content ```json { "nodes": ["http://[ip-of-another-node-or-127.0.0.1-for-your-local-machine]:[the-port-number]"] } ``` to `http://[the-node-ip-you-want-to-register-it-to]:[port]/nodes/add` ## Step 20: Consensus check After that try to mine some blocks and even add some transactions on let's say node 2 and then run `http://[a-node-ip]:[port]/nodes/resolve` on let's say node 1. The consensus algorithm should step into action and update the blockchain of node 1. # The whole thang I keep my promises ```python import hashlib import json import requests from time import time from uuid import uuid4 from textwrap import dedent from flask import Flask, jsonify, request from urllib.parse import urlparse class MyBlockChain(object): def __init__(self): self.blockchain = [] self.transactions = [] # Creation of the mentioned genesis block self.create_new_block(previous_hash=1, proof=100) self.nodes = set() def create_new_block(self, proof, previous_hash=None): """ Creates a new block and adds it to the blockchain :param proof: <int> This is generated by the proof of work algorithm :param previous_hash: (Optional) <str> Hash of the preleading Block :return: <dict> Return the new block """ new_block = { 'index': len(self.blockchain) + 1, 'timestamp': time(), 'transactions': self.transactions, 'proof': proof, 'previous_hash': previous_hash or self.hash(self.blockchain[-1]), } # As all pending transactions have been processed and added to the block, the list can be resetted self.transactions = [] # Add the new block to the blockchain self.blockchain.append(new_block) return new_block def create_new_transaction(self, sender, recipient, amount): """ This function creates a new transaction that will then be placed in a new block, alone or bundled together with other transactions. :param sender: <str> Sender's address :param recipient: <str> Recipient's address :param amount: <int> Amount to be transferred :return: <int> This is the index of the block that will contain this transaction """ self.transactions.append({ 'sender': sender, 'recipient': recipient, 'amount': amount, }) return self.last_block['index'] + 1 @staticmethod def hash(block): """ This function hashes the block using the SHA-256 hash algorithm The function is given a block and returns a string, consisting of the hash :param block: <dict> Block :return: <str> """ # As every change in an item changes the hash, we first have to do a little sort operation, or else we would get inconsistent hashes block_sorted = json.dumps(block, sort_keys=True).encode() return hashlib.sha256(block_sorted).hexdigest() @property def last_block(self): return self.blockchain[-1] def pow(self, last_proof): """ Simple PoW Algorithm: - Find a number y, so that hash(xy) starts with 5 zeroes. x is the last y aka last_proof. y is then the new proof. :param last_proof: <int> :return: <int> """ current_proof = 0 while self.validate_proof(last_proof, current_proof) is False: current_proof += 1 return current_proof @staticmethod def validate_proof(last_proof, current_proof): """ Returns, whether the hash of the lastproof and the current_proof contains 5 leading zeroes. :param last_proof: <int> Previous Proof Number :param current_proof: <int> Current Proof Number :return: <bool> """ possible_hash = hashlib.sha256(f'{last_proof}{current_proof}'.encode()).hexdigest() return possible_hash[:5] == "00000" def add_node(self, address): """ Register a new node :param address: <str> This is the new node's address, for example 'http://192.168.1.112:5000' :return: None """ node_url = urlparse(address) self.nodes.add(node_url.netloc) def validate_blockchain(self, test_chain): """ Evaluate, whether a blockchain is valid :param chain: <list> The blockchain that shall be tested :return: <bool> Returns true if the blockchain is valid """ last_block = test_chain[0] current_index = 1 while current_index < len(test_chain): block = test_chain[current_index] # Determine, whether the hash is correct if block['previous_hash'] != self.hash(last_block): return False # Determine, wheter the proof of work is correct if not self.validate_proof(last_block['proof'], block['proof']): return False last_block = block current_index += 1 return True def resolve(self): """ This algorithm resolves conflicts between our nodes. It is the consensus algorithm which I mentioned previously. :return: <bool> Returns true, if our chain was substituted with an updated version """ surrounding_nodes = self.nodes updated_chain = None # If we follow our consensus algorithm description, we only want blockchains that are longer, than our current chain max_length = len(self.blockchain) # Iterate every surrounding nodes in our network through the consensus algorithm, which means checking if the node's blockchain is longer than our current blockchain and valid and set it as our new blockchain and continue checking, as there could be an even longer and valid blockchain. for node_iterator in surrounding_nodes: response = requests.get(f'http://{node_iterator}/blockchain') if response.status_code == 200: length = response.json()['length'] chain_iterator = response.json()['chain'] if length > max_length and self.validate_blockchain(chain_iterator): max_length = length updated_chain = chain_iterator # If we found a new blockchain, replace our current blockchain with the new one if updated_chain: self.blockchain = updated_chain return True return False app = Flask(__name__) node_identifier = str(uuid4()).replace('-', '') myblockchain = MyBlockChain() @app.route('/blockchain', methods=['GET']) def get_full_chain(): output = { 'chain': myblockchain.blockchain, 'length': len(myblockchain.blockchain), } return jsonify(output), 200 @app.route('/mining', methods=['GET']) def mining(): # Calculate the new proof by using our PoW algorithm last_block = myblockchain.last_block last_proof = last_block['proof'] proof = myblockchain.pow(last_proof) # For finding/mining the proof, the miner is granted a reward # The sender is nobody, as this coin is coming out of the void myblockchain.create_new_transaction( sender="0", recipient=node_identifier, amount=1, ) # Add the new created block to the chain previous_hash = myblockchain.hash(last_block) newblock = myblockchain.create_new_block(proof, previous_hash) output = { 'message': "A new block was mined", 'index': newblock['index'], 'transactions': newblock['transactions'], 'proof': newblock['proof'], 'previous_hash': newblock['previous_hash'], } return jsonify(output), 200 @app.route('/transactions/add', methods=['POST']) def add_transaction(): values = request.get_json() # The POST request has to have the following required fields required = ['sender', 'recipient', 'amount'] if not all(k in values for k in required): return 'There are values missing', 400 # Adds a new transaction by utilizing our function index = myblockchain.create_new_transaction(values['sender'], values['recipient'], values['amount']) output = {'message': f'Your registered Transaction is going to be a part of the block with the index of {index}'} return jsonify(output), 201 @app.route('/nodes/add', methods=['POST']) def add_nodes(): values = request.get_json() nodes = values.get('nodes') if nodes is None: return "You didn't post a valid list of nodes. Please double check your input!", 400 for node in nodes: myblockchain.add_node(node) response = { 'message': 'All of your specified nodes have been added to the network!', 'total_nodes': list(myblockchain.nodes), } return jsonify(response), 201 @app.route('/nodes/resolve', methods=['GET']) def consensus(): replaced = myblockchain.resolve() if replaced: response = { 'message': 'There was a longer valid chain within the network. The blockchain of this node has been replaced.', 'new_chain': myblockchain.blockchain } else: response = { 'message': 'The blockchain of this node is already the longest valid chain within the network.', 'chain': myblockchain.blockchain } return jsonify(response), 200 if __name__ == '__main__': app.run(host='0.0.0.0', port=5000) ``` # Final thoughts And there you have it! Your very own blockchain. Wasn't very hard, was it? I sincerely hope you had fun thorughout this tutorial and were able to understand the concept and system behind it better. If you have any questions, please ask them in the comments and I'll try my best to answer them. # The obligatory begging As this whole tutorial took me over 2 days to finish, I would love to see a lot of comments and feedback under this post. Also if you find any typos, grammar mistakes, etc. and care to tell me, i would be mor than happy about it, as English is not my native language. So please excuse any mistakes I made. I tried my very best. Of course please upvote, if you worship my effort to enrich the community, and if you want to see more such content, consider following me. I wish you only the best - See ya!
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parent author
parent permlink	steemit
permlink	create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
title	Create your own blockchain & cryptocurrency! - understand blockchains by creating one in python - no knowledge required
Transaction Info	Block #18742267/Trx 0db3d5121f95452bf55e53ad31c21e9b92ec940b

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      "author": "dustvoice",
      "body": "# What exactly is a blockchain?\n- How does a blockchain work?\n- What is Bitcoin or STEEM exactly?\n- How does a blockchain make sure of its correctness\n- What is **mining** exactly?\n\n**These are only some questions, probably many of you are asking yourselves. \nI'm here to provide you with kind of an unusual answer.\nMy goal is to help you undestand the whole system behind blockchains, by actually creating a small blockchain yourself!**\n\nWith the rise of cryptocurrencies and decentralized systems like Bitcoin or STEEM, many people want to really undestand, what this is all about. I will show you how the system works, by coding a blockchain from scratch in python with you. The guide will be mainly for Windows, but I will also add comments regarding Linux. You don't know a whole of python, to follow this guide, but it is advised to know the most basic basics.\n\n# Get ready\n## Setup Python and pip\nFirst off, we need to install Python 3.6+ along with pip, with which you can install python packages. \n- On **Linux**, you can install python, by simply typing `sudo apt-get install python3.6` into the terminal. If you encounter errors, please try `sudo apt-get update` and then try to execute the command again. If it still doesn't work, please search for installation instructions for your specific system on your preferred search engine.\n- On **Windows**,\n  1. first download the binary, that suits your system best, under the [official python download page for windows.](https://www.python.org/downloads/windows/). Make sure you grab at least the _version 3.6_ or higher.\n  2. Install the file you just downloaded. Make sure you check the option to install pip, when provided with an option to do so. If not, don't worry, it probably is enabled by default.\n\n## IDE or not?\nAs a next step, you want to decide, whether to utilize an [IDE](https://en.wikipedia.org/wiki/Integrated_development_environment) or not. An IDE is an environment, which supports you in the creation process of your application, by providing many features, with for example syntax highlighting, or code completion, to name just 2 possible features. My favorite IDE for Python development is probably PyCharm, which you can fetch from [this link.](https://www.jetbrains.com/pycharm) Setting up PyCharm on Windows is as simple, as downloading the executable installer and installing it with the provided setup utility. PyCharm is free tu use, as long as you use the Community Edition.\nYou can also use your coding notepad of choice. We will only work in one file, which you have to execute, so as long as your text-editing software is able to produce files with the ending `.py`, it will work fine.\n\n## Setup your workspace (PyCharm)\nIf you decided to use PyCharm, simply open it up and click on _Create Project_ in the popup dialogue. In the next dialogue you want to specify your project's name. I chose to use _MyBlockChain_ as my project name. Finally click on _create_ in the bottom right corner. On your left hand side, you're now provided with a file tree. \n1. Right-Click on the folder which consists of your project's name, in my case _MyBlockChain_\n2. Go to _new_ \n3. Finally click on _Python File_ and\n4. Define a Filename. I chose `MyBlockChain.py` as my filename.\n\n## Create your file (Simple Text Editor)\nIf you use a simple text editor, just create a file anywhere you like with the file extension `.py`. In my case I chose to use the filename `MyBlockChain.py`.\n\n## Install the needed packages\n### PyCharm\nIn PyCharm you can install packages very easily and add them to your project:\n1. Make sure, you have your project open\n2. Go to _File_ -> _Settings_ -> _Project: [your project name]_ -> _Project Interpreter_\n3. Then click on the green plus symbol.\n4. In the search field type in _Flask_ first. Select the first entry, which simply says _Flask_. Then click on Install Package in the bottom left corner.\n5. Do the same thing for _Requests_.\n### Pip\nIf you chose not to use PyCharm, you simply need to open up the terminal on linux or the command prompt, or PowerShell on Windows _(simply press **Windows+R** and type in cmd)_ and then execute `pip install Flask==0.12.2 requests==2.18.4 `. If this gives you an error, please double check that you have _pip_ installed. If the problem still occurs, please troubleshoot the error message using google, as there are too many possibilities, what the error could be caused by, for me to discuss every one of them here.\n\n## Getting a HTTP-Client\nYou will also need a HTTP-Client, as we need to make `GET` and `POST` requests to our Flask instance, at some Point in time. Mainly, there are two options - [_Postman_](https://www.getpostman.com/) or [_cURL_](https://curl.haxx.se/). I highly recommend _Postman_, as it is easy and intuitive to use, but if you just want a simple and quick solution, without having to register for an account, just use _cURL_. Online solutions, probably won't work, as the webserver you are going to be trying to access, is just on your local machine. \n\n## Just gimme the source code!\nIf you just want the source code and don't want to follow my instructions, please scroll down, to the very end of this post, where I will add the source code in its complete beauty.\n\n# The Blockchain - Your Blockchain\n## Step 1: Creating a simplistic Blockchain\nA block chain is basically a chain of blocks that are linked together in some way, as you have already figured. In this case, every block contains a hash of the previous block. A hash is a hexadecimal number that is determined by a specific algorithm. Imagine a hash being a digital fingerprint of an item. A good hash algorithm will never return the same hash for two different items, so every hash is individual. In our case we will be using the [_SHA-256_](https://en.wikipedia.org/wiki/SHA-2) algorithm. Furthermore the hash algorithm is not reversible, so you can't determine the object, by having its hash, but you can always apply the hash algorithm on the object, to get its hash. As every item has the hash of its previous item, the blockchain is protected against violation, as one would have to change every following block, as the hash changes with every change, as two different items can't have the same hash.\n### The Blockchain class\nOur Blockchain class basically consists of a constructor and some functions. In the constructor, we will create two empty lists - one to store our blockchain in and another, for our transactions. As for now, our class will have several functions:\n- A function to create new blocks\n- A function to create new transactions\n- A function, which hashes a block\n- A function to fetch the last block\nThe python template looks like this:\n```python\nclass MyBlockChain(object):\n    def __init__(self):\n        self.blockchain = []\n        self.transactions = []\n        \n    def create_new_block(self):\n        # This function creates a new block and appends it to the chain\n        pass\n    \n    def create_new_transaction(self):\n        # This function creates a new transaction and adds it to the list of transactions\n        pass\n    \n    @staticmethod\n    def hash(block):\n        # This method hashes the passed block\n        pass\n\n    @property\n    def last_block(self):\n        # This function returns the last block in the chain\n        pass\n```\n## Step 2: The blocks\nAs described earlier, a blockchain consists of blocks. So I will cover them first.\nEach Block has 5 fields:\n- An index,\n- an Unix timestamp,\n- a list of transactions,\n- a proof,\n- and finally the hash of the previous block.\nJust to clarify things, here is an example of a block\n```json\nexample_block = {\n    'index': 5,\n    'timestamp': 1515110045.123456,\n    'transactions': \n    [\n        {\n            'sender': \"154d8554f9541e12354e1234f512a001\",\n            'recipient': \"8654e21254c6512a51bce156542d1e5c\",\n            'amount': 212,\n        }\n    ],\n    'proof': 488612354568,\n    'previous_hash': \"c7be1ed902fb8dd4d48997c6452f5d7e509fbcdbe2808b16bcf4edce4c07d14e\"\n}\n```\n## Step 3: Hashing it\nAs every block needs the hash of the previous block, we need a function, that calculates the hash of a block. To accomplish this, we simply modify our empty `hash` function\n```python\nimport hashlib\nimport json\n\nclass MyBlockChain(object):\n    [...]\n    @staticmethod\n    def hash(block):\n        \"\"\"\n        This function hashes the block using the SHA-256 hash algorithm\n        The function is given a block and returns a string, consisting of the hash\n        :param block: <dict> Block\n        :return: <str>\n        \"\"\"\n\n        # As every change in an item changes the hash, we first have to do a little sort operation, or else we would get inconsistent hashes\n        block_sorted = json.dumps(block, sort_keys=True).encode()\n        return hashlib.sha256(block_sorted).hexdigest()\n```\n## Step 4: Transactions\nOur `create_new_transaction` method is responsible for adding new transactions to the `transactions` list, which will then be stored inside a block. The whole function is pretty self explanatory. But first we need a function to return the last block of the chain, as we will calculate the new index, at which the transaction will be stored, by increasing the index of the last block by 1\n```python\nclass MyBlockChain(object):\n    [...]\n    @property\n    def last_block(self):\n        return self.blockchain[-1]\n```\nNow we can fill out the `create_new_transaction` function\n```python\nclass MyBlockChain(object):\n    [...]\n    def create_new_transaction(self, sender, recipient, amount):\n        \"\"\"\n        This function creates a new transaction that will then be placed in a new block, alone or bundled together with other transactions.\n        \n        :param sender: <str> Sender's address\n        :param recipient: <str> Recipient's address\n        :param amount: <int> Amount to be transferred\n        :return: <int> This is the index of the block that will contain this transaction\n        \"\"\"\n\n        self.transactions.append({\n            'sender': sender,\n            'recipient': recipient,\n            'amount': amount,\n        })\n\n        return self.last_block['index'] + 1\n```\n## Step 5: Creating new Blocks\nBy now we almost have everything at our hands, what we need in order to make a new block. The only thing missing is the _proof_ field. As this is a little harder to understand, I will explain it later. \nBut we still have one problem - if every block has the hash of the previous block, what shall we do with our first block, as there is no previous block for us to hash. \nThis first block is called the _genesis_ block.\n```python\nimport hashlib\nimport json\nfrom time import time\n\nclass MyBlockChain(object):\n    def __init__(self):\n        self.blockchain = []\n        self.transactions = []\n\n        # Creation of the mentioned genesis block\n        self.create_new_block(previous_hash=1, proof=100)\n\n    def create_new_block(self, proof, previous_hash=None):\n        \"\"\"\n        Creates a new block and adds it to the blockchain\n        :param proof: <int> This is generated by the proof of work algorithm\n        :param previous_hash: (Optional) <str> Hash of the preleading Block\n        :return: <dict> Return the new block\n        \"\"\"\n\n        new_block = {\n            'index': len(self.blockchain) + 1,\n            'timestamp': time(),\n            'transactions': self.transactions,\n            'proof': proof,\n            'previous_hash': previous_hash or self.hash(self.blockchain[-1]),\n        }\n\n        # As all pending transactions have been processed and added to the block, the list can be resetted\n        self.transactions = []\n        \n        # Add the new block to the blockchain\n        self.blockchain.append(new_block)\n        return new_block\n```\n##  Step 6: What's up with the proof?!\n### The [Proof of Work (PoW) algorithm](https://en.wikipedia.org/wiki/Proof-of-work_system)\nThis system wants to **proof** that work has been done. Now a little bit less abstract. Basically we are searching for a number that matches a specific criteria. The thing is, for the system to work, the process of finding a number matching the criteria has to be **difficult**, but the verification process has to be **quick and easy**. This is how new blocks are created, or expressed in another, more commonly used term, _mined_.\n#### Still too abstract? Ok here is an example:\nWe are looking for a hash of a product of two integers that ends with a 1.\nSo the result of the multiplication of `a` and `b` gets hashed and has to end with a 1. If we set a to `a` static value, our algorithm will determine a value for `b`, for which this criteria is matched. \n```python\nfrom hashlib import sha256\na = 12\nb = 0  # We don't know what b has to be. It will be determined by the algorithm\nwhile sha256(f'{a*b}'.encode()).hexdigest()[-1] != \"1\":\n    b += 1\nprint(f'The solution is b = {b}')\n```\nThis example outputs\n```\nThe solution is b = 4\n```\nThis means that the hash of `12*4` ends with a 1\n```\nhash(48) = 98010bd9270f9b100b6214a21754fd33bdc8d41b2bc9f9dd16ff54d3c34ffd71\n```\nAs you can tell, the verification process doesn't need countless loops, until it finds a matching pair. You just have to run the hash algorithm once on the numbers and you can easily determine, whether the numbers match the criteria, or not.\n## Step 7: Implementing PoW\nFirstoff, we need a criteria, or commonly referred to as a rule. For now, our rule is that the hash has to have 5 leading zeroes, so `000005bc845e...` would be a valid result, but `000019ea76c4` would not. As the difficulty rises extremely, if we would require 6 leading zeros, the difficulty of our simple algorithm can be adjusted by changing the amount of leading zeroes required. This is the implementation in python:\n```python\n[...]\nfrom uuid import uuid4\n\nclass MyBlockChain(object):\n    [...]\n        \n    def pow(self, last_proof):\n        \"\"\"\n        Simple PoW Algorithm:\n         - Find a number y, so that hash(xy) starts with 5 zeroes. x is the last y aka last_proof. y is then the new proof.\n        :param last_proof: <int>\n        :return: <int>\n        \"\"\"\n        \n        current_proof = 0\n        while self.validate_proof(last_proof, current_proof) is False:\n            current_proof += 1\n\n        return current_proof\n\n    @staticmethod\n    def validate_proof(last_proof, current_proof):\n        \"\"\"\n        Returns, whether the hash of the lastproof and the current_proof contains 5 leading zeroes.\n        :param last_proof: <int> Previous Proof Number\n        :param current_proof: <int> Current Proof Number\n        :return: <bool>\n        \"\"\"\n\n        possible_hash = hashlib.sha256(f'{last_proof}{current_proof}'.encode()).hexdigest()\n        return possible_hash[:5] == \"00000\"\n```\n## Step 8: Interacting with our class\nNow we are able to create a blockchain. But we can't really interact with it, as we have only interacted with the functions and variables of our class.\nWe are going to use HTTP requests to interact with our blockchain. So let's set it up!\n# HTTP in the house!\nTo talk to our blockchain using Http requests, we need some help - which comes in the form of the _Flask Framework_. We will create and implement 3 basic methods for now:\n- `/blockchain` to retrieve the full blockchain\n- `/mining` to make our simple server mine a block\n- `/transactions/add` to add a new transaction to the blockchain.\n## Step 9: Flask\nFirst we need to implement Flask. Here is the code:\n```python\n[...]\nfrom textwrap import dedent\nfrom flask import Flask, jsonify, request\n\nclass MyBlockChain(object):\n    [...]\n    \napp = Flask(__name__)\nnode_identifier = str(uuid4()).replace('-', '')\n\nmyblockchain = MyBlockChain()\n\[email protected]('/blockchain', methods=['GET'])\ndef get_full_chain():\n    output = {\n        'chain': myblockchain.blockchain,\n        'length': len(myblockchain.blockchain),\n    }\n    return jsonify(output), 200\n\[email protected]('/mining', methods=['GET'])\ndef mining():\n    pass\[email protected]('/transactions/add', methods=['POST'])\ndef add_transaction():\n    pass\nif __name__ == '__main__':\n    app.run(host='0.0.0.0', port=5000)\n```\n## Step 10: Adding Transactions\nAs this is commonly the main task of a block chain and also required for a new block, I will cover this first. The user sends a _POST request_ to `/transactions/add` with a JSON object, containing all required fields. This is an example, for a possible, valid request:\n```json\n{\n \"sender\": \"154d8554f9541e12354e1234f512a001\",\n \"recipient\": \"8654e21254c6512a51bce156542d1e5c\",\n \"amount\": 212\n}\n```\nAs you can see, a request has three fields:\n- A _sender_ field, with the sender id,\n- a _recipient_ field, with the recipient id\n- and an amount, which defines how many units are to be transferred\nNow we just need to implement this function\n```python\n[...]\n\[email protected]('/transactions/add', methods=['POST'])\ndef add_transaction():\n    values = request.get_json()\n\n    # The POST request has to have the following required fields\n    required = ['sender', 'recipient', 'amount']\n    if not all(k in values for k in required):\n        return 'There are values missing', 400\n\n    # Adds a new transaction by utilizing our function\n    index = myblockchain.create_new_transaction(values['sender'], values['recipient'], values['amount'])\n\n    output = {'message': f'Your registered Transaction is going to be a part of the block with the index of {index}'}\n    return jsonify(output), 201\n```\nThis function simply calls the `create_new_transaction` method with the parameters of the POST request\n## Step 11: Setup your mines\nAs discussed earlier, future blocks have to be mined. If a new block is found/mined, all pending transactions are added to this block. To 'mine' a new block, our function hast to do three things\n1. Calculate the proof\n2. Reward the miner with a specific amount of coins (in our example 1 coin)\n3. Add the new mined block to the blockchain\n_(The fact that the recipient is our current node, will make more sense, as we will talk about decentralization later on.)_\n```python\[email protected]('/mining', methods=['GET'])\ndef mining():\n    # Calculate the new proof by using our PoW algorithm\n    last_block = myblockchain.last_block\n    last_proof = last_block['proof']\n    proof = myblockchain.pow(last_proof)\n\n    # For finding/mining the proof, the miner is granted a reward\n    # The sender is nobody, as this coin is coming out of the void\n    myblockchain.create_new_transaction(\n        sender=\"0\",\n        recipient=node_identifier,\n        amount=1,\n    )\n\n    # Add the new created block to the chain\n    previous_hash = myblockchain.hash(last_block)\n    newblock = myblockchain.create_new_block(proof, previous_hash)\n\n    output = {\n        'message': \"A new block was mined\",\n        'index': newblock['index'],\n        'transactions': newblock['transactions'],\n        'proof': newblock['proof'],\n        'previous_hash': newblock['previous_hash'],\n    }\n    return jsonify(output), 200\n```\n# Hello World!\nNow, **finally** we will be interacting with our blockchain API. Grab your HTTP client of choice and get going! I will explain the procedure for Postman and cURL.\n## Step 12: Start up the chain\nFirst off fire up your server. \nIn PyCharm simply click on _Run_ -> _Run..._ and select _[your filename].py_ as the file to run, in my case _myblockchain.py_.\nIf you chose to use a simple python file without an IDE, fire up a terminal or command prompt window inside the directory your file is located in and execute the following command\n```\npython blockchain.py\n```\nas a result you will see something similar to this\n```\n$ python blockchain.py\n* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)\n```\n**Note that you may be prompted with a dialogue of your firewall. Just accept it.**\n## Step 13: Mining it all!\nOk let's try the most exciting thing first, **mining**. I'm sure you can't wait to mine your first block, so let's do it!\nAs you can see in the code\n```python\n[...]\[email protected]('/mining', methods=['GET'])\ndef mining():\n    [...]\n```\nwe will be interacting with the `mining` part of our API through `GET` requests. This makes sense, as our only goal with this part of the API is, to mine a new block. We don't have to pass anything to the function at all, so a `GET` request is the way to go.\n### Postman\nIf you chose to use Postman, here is a quick tutorial on how to make a post request. \n1. First you have to register for an account, if you haven't already done that\n2. and login after that. \n3. If you are logged in, you shoudl be provided with several options such as _Request_, _Collection_, _Environment_.\n4. You could simply use the option _Request_, but to keep things organized, we are going to select the _Collection_ option. \n5. After that simply choose a name for your collection, in my case I'm using _MyBlockChain_ as my name.\n6. Now click on the _New_ Button, located in the top left corner and select _Request_ this time. We are now going to be creating 3 requests.\n7. The first request is going to be our _mining_ request, second is a _new transaction_ request and finally we will have a _get whole blockchain_ request. Of course you can customize the request names as you like. \n8. **Make sure, as you create these 3 requests, that you select our newly created Collection in the bottom section of the dialogue!**\n9. Now click on our Collection's folder in the left sidebar. You should see your 3 newly created requests. Select the _mining_ request first.\n10. On the right you are now provided with an interface. As you can see by the selected item from the dropdown box, left to the text field, a `GET` request is the standard request type, so we don't have to change that yet. \n11. In the text field `Enter request URL` we are now going to enter the `mining` URL of our API, so enter `http://localhost:5000/mining` as the request URL.\n### cURL\nIf you chose to use cURL as your HTTP client, simply type `curl -i -H \"Content-Type: application/json\" -X GET http://localhost:5000/mining` in a terminal window\n### Either way\nWith both methods you should see something similar to this as a result\n```json\n{\n    \"index\": 2,\n    \"message\": \"New Block Forged\",\n    \"previous_hash\": \"0f9cb2f06100899cb31b85fef221e243d1088c0aa6840a568e58d4a27dbd186a\",\n    \"proof\": 888273,\n    \"transactions\": [\n        {\n            \"amount\": 1,\n            \"recipient\": \"491002ea048a42609d967027cc46a07b\",\n            \"sender\": \"0\"\n        }\n    ]\n}\n```\n## Step 14: Transactions are great!\nAs our mining algorithm seems to be working fine, let's create a new transaction, to be stored in a fresh mined block. To do that in\n### Postman\n1. Click on the _new transaction_ request in the left sidebar.\n2. Click on the _GET_ button with the small arrow pointing down.\n3. Select _POST_ from the drop-down list.\n4. In the navbar below the text field, select _Body_ \n5. and then mark the _raw_ option.\n6. You should now be provided with an editor like text area, and another drop-down menu next to the _binary_ option, where _Text_ is currently selected. Select _JSON (application/json)_ from this list.\n7. Now type in the following into the text area.\n```json\n{\n \"sender\": \"your-node-address\",\n \"recipient\": \"another-node-address\",\n \"amount\": 212\n}\n```\n### cURL\nJust execute `curl -X POST -H \"Content-Type: application/json\" -d '{\"sender\": \"your-node-address\", \"recipient\": \"another-node-address\", \"amount\": 212}' \"http://localhost:5000/transactions/add\"` in a terminal window.\n### In both cases\nReplace `your-node-address` with the _recipient_ address from you mining request, as this is your node address. You can also select any other 32 digit hexadezimal number, for now. Furthermore replace `another-node-address` with a random 32 digit hexadezimal number for now, as we currently don't have any other nodes.\nAdjust the `amount` to your liking.\nAnd **voilà**! You have registered your first transaction!\n## Step 15: The Chain...\nSo let's inspect our chain! If you're using\n### Postman\nClick on the _get whole blockchain_ request in the left sidebar and simply enter `http://localhost:5000/blockchain` in the `Enter request URL` text field, as _GET_ should be preselected. If not, please change it to the _GET_ option.\n### cURL\njust execute  `curl -i -H \"Content-Type: application/json\" -X GET http://localhost:5000/blockchain` in a terminal window.\n### Either way\nyou should get your whole blockchain in form of a JSON-Object. In my case, my blockchain looks like this, after mining 2 times, adding 3 transactions and mining another block:\n```json\n{\n    \"chain\": [\n        {\n            \"index\": 1,\n            \"previous_hash\": \"1\",\n            \"proof\": 100,\n            \"timestamp\": 1515156902.4502413,\n            \"transactions\": []\n        },\n        {\n            \"index\": 2,\n            \"previous_hash\": \"0f9cb2f06100899cb31b85fef221e243d1088c0aa6840a568e58d4a27dbd186a\",\n            \"proof\": 888273,\n            \"timestamp\": 1515156913.2686973,\n            \"transactions\": [\n                {\n                    \"amount\": 1,\n                    \"recipient\": \"491002ea048a42609d967027cc46a07b\",\n                    \"sender\": \"0\"\n                }\n            ]\n        },\n        {\n            \"index\": 3,\n            \"previous_hash\": \"1d2ae4a41f4a82ce6f04944e8227bf9c4d951d560f8763b910d7314634dfe09c\",\n            \"proof\": 1156297,\n            \"timestamp\": 1515158367.3596537,\n            \"transactions\": [\n                {\n                    \"amount\": 212,\n                    \"recipient\": \"d4ee26eee15148ee92c6cd394edd974e\",\n                    \"sender\": \"491002ea048a42609d967027cc46a07b\"\n                },\n                {\n                    \"amount\": 212,\n                    \"recipient\": \"5654c5654e1b551a65e15f5e4651c156\",\n                    \"sender\": \"491002ea048a42609d967027cc46a07b\"\n                },\n                {\n                    \"amount\": 111,\n                    \"recipient\": \"491002ea048a42609d967027cc46a07b\",\n                    \"sender\": \"5654c5654e1b551a65e15f5e4651c156\"\n                },\n                {\n                    \"amount\": 1,\n                    \"recipient\": \"491002ea048a42609d967027cc46a07b\",\n                    \"sender\": \"0\"\n                }\n            ]\n        }\n    ],\n    \"length\": 3\n}\n```\n# Decentralizing it\nOk, so we got a blockchain, that's working fine and we can interact with it. But one very important thing is still missing: **Decentralization**. \nThis is a core element of the blockchain idea. \nFirst off by decentralizing the whole thing, safety and integrity of the blockchain is guaranteed, as a change in the blockchain will be recognized, by the other nodes, as they also have a copy of the blockchain, and discarded. \nThe second reason is that we somehow have to make sense of our transactions. For this we need other nodes and why shouldn't they contribute to our network, by being a part of the blockchain system?! \nBut we still have a conflict there: What if a node has a blockchain that differs from all the others? \nFor our simple blockchain we will always make the **longest valid** blockchain authorative.\n## Step 16: Someone out there?!\nBut first things first. \nTo get started, we first have to implement other nodes into our system.\nTo accomplish this task, we have to adjust a few things in our API. First off, we are going to implement some new endpoints:\n1. `/nodes/add` to add new nodes in form of a list of URLs\n2. `/nodes/resolve` to resolve the conflict we discussed previously by using a consensus algorithm.\nTo do this, we have to modify our Blockchain class first:\n```python\n[...]\nfrom urllib.parse import urlparse\n\nclass MyBlockChain(object):\n    def __init__(self):\n        [...]\n        self.nodes = set()\n\n    def add_node(self, address):\n        \"\"\"\n        Register a new node\n        :param address: <str> This is the new node's address, for example 'http://192.168.1.112:5000'\n        :return: None\n        \"\"\"\n\n        node_url = urlparse(address)\n        self.nodes.add(node_url.netloc)\n```\n## Step 17: We need Consensus\nTo resolve the conflict of differing blockchains between the nodes, we are going to implement a consensus algorithm. As we discussed earlier, we are always utilizing the longest valid blockchain.\nFirst we are implementing a function that validates a blockchain:\n```python\n[...]\nimport requests\n\nclass MyBlockChain(object)\n    [...]\n    \n    def validate_blockchain(self, test_chain):\n        \"\"\"\n        Evaluate, whether a blockchain is valid\n        :param chain: <list> The blockchain that shall be tested\n        :return: <bool> Returns true if the blockchain is valid\n        \"\"\"\n\n        last_block = test_chain[0]\n        current_index = 1\n\n        while current_index < len(test_chain):\n            block = test_chain[current_index]\n            \n            # Determine, whether the hash is correct\n            if block['previous_hash'] != self.hash(last_block):\n                return False\n\n            # Determine, wheter the proof of work is correct\n            if not self.validate_proof(last_block['proof'], block['proof']):\n                return False\n\n            last_block = block\n            current_index += 1\n\n        return True\n```\nNow we just have to run every blockchain in our surrounding network through this consensus algorithm:\n```python\n [...]\n\nclass MyBlockChain(object)\n    [...]\n    def resolve(self):\n        \"\"\"\n        This algorithm resolves conflicts between our nodes. It is the consensus algorithm which I mentioned previously.\n        :return: <bool> Returns true, if our chain was substituted with an updated version\n        \"\"\"\n\n        surrounding_nodes = self.nodes\n        updated_chain = None\n\n        # If we follow our consensus algorithm description, we only want blockchains that are longer, than our current chain\n        max_length = len(self.blockchain)\n\n        # Iterate every surrounding nodes in our network through the consensus algorithm, which means checking if the node's blockchain is longer than our current blockchain and valid and set it as our new blockchain and continue checking, as there could be an even longer and valid blockchain.\n        for node_iterator in surrounding_nodes:\n            response = requests.get(f'http://{node_iterator}/blockchain')\n\n            if response.status_code == 200:\n                length = response.json()['length']\n                chain_iterator = response.json()['chain']\n\n                if length > max_length and self.validate_blockchain(chain_iterator):\n                    max_length = length\n                    updated_chain = chain_iterator\n\n        # If we found a new blockchain, replace our current blockchain with the new one\n        if updated_chain:\n            self.blockchain = updated_chain\n            return True\n\n        return False\n```\nNow we just have to register our new functions as new endpoints in the API:\n```python\[email protected]('/nodes/add', methods=['POST'])\ndef add_nodes():\n    values = request.get_json()\n\n    nodes = values.get('nodes')\n    if nodes is None:\n        return \"You didn't post a valid list of nodes. Please double check your input!\", 400\n\n    for node in nodes:\n        myblockchain.add_node(node)\n\n    response = {\n        'message': 'All of your specified nodes have been added to the network!',\n        'total_nodes': list(myblockchain.nodes),\n    }\n    return jsonify(response), 201\n\n\[email protected]('/nodes/resolve', methods=['GET'])\ndef consensus():\n    replaced = myblockchain.resolve()\n\n    if replaced:\n        response = {\n            'message': 'There was a longer valid chain within the network. The blockchain of this node has been replaced.',\n            'new_chain': myblockchain.blockchain\n        }\n    else:\n        response = {\n            'message': 'The blockchain of this node is already the longest valid chain within the network.',\n            'chain': myblockchain.blockchain\n        }\n\n    return jsonify(response), 200\n```\n## Step 18: Friends are great. Even if they're virtual...\nTo test our decentralization algorithms, either grab some friends, to run some nodes for you, or just run the same program on different ports, so you would have to start up an instance of our blockchain-program, then change to port to 5001 for example, save, fire up an instance of this _modified_ program, change the port to 5002, etc. \n## Step 19: Add them to your friends list\nIf you got some instances, you just have to register them. To do this, simply send a `POST` request with the following content\n```json\n{\n    \"nodes\": [\"http://[ip-of-another-node-or-127.0.0.1-for-your-local-machine]:[the-port-number]\"]\n}\n```\nto `http://[the-node-ip-you-want-to-register-it-to]:[port]/nodes/add`\n## Step 20: Consensus check\nAfter that try to mine some blocks and even add some transactions on let's say node 2 and then run `http://[a-node-ip]:[port]/nodes/resolve` on let's say node 1. The consensus algorithm should step into action and update the blockchain of node 1.\n# The whole thang\nI keep my promises\n```python\nimport hashlib\nimport json\nimport requests\nfrom time import time\nfrom uuid import uuid4\nfrom textwrap import dedent\nfrom flask import Flask, jsonify, request\nfrom urllib.parse import urlparse\n\nclass MyBlockChain(object):\n    def __init__(self):\n        self.blockchain = []\n        self.transactions = []\n        \n        # Creation of the mentioned genesis block\n        self.create_new_block(previous_hash=1, proof=100)\n        \n        self.nodes = set()\n        \n    def create_new_block(self, proof, previous_hash=None):\n        \"\"\"\n        Creates a new block and adds it to the blockchain\n        :param proof: <int> This is generated by the proof of work algorithm\n        :param previous_hash: (Optional) <str> Hash of the preleading Block\n        :return: <dict> Return the new block\n        \"\"\"\n\n        new_block = {\n            'index': len(self.blockchain) + 1,\n            'timestamp': time(),\n            'transactions': self.transactions,\n            'proof': proof,\n            'previous_hash': previous_hash or self.hash(self.blockchain[-1]),\n        }\n\n        # As all pending transactions have been processed and added to the block, the list can be resetted\n        self.transactions = []\n        \n        # Add the new block to the blockchain\n        self.blockchain.append(new_block)\n        return new_block\n    \n    def create_new_transaction(self, sender, recipient, amount):\n        \"\"\"\n        This function creates a new transaction that will then be placed in a new block, alone or bundled together with other transactions.\n        \n        :param sender: <str> Sender's address\n        :param recipient: <str> Recipient's address\n        :param amount: <int> Amount to be transferred\n        :return: <int> This is the index of the block that will contain this transaction\n        \"\"\"\n\n        self.transactions.append({\n            'sender': sender,\n            'recipient': recipient,\n            'amount': amount,\n        })\n\n        return self.last_block['index'] + 1\n    \n    @staticmethod\n    def hash(block):\n        \"\"\"\n        This function hashes the block using the SHA-256 hash algorithm\n        The function is given a block and returns a string, consisting of the hash\n        :param block: <dict> Block\n        :return: <str>\n        \"\"\"\n\n        # As every change in an item changes the hash, we first have to do a little sort operation, or else we would get inconsistent hashes\n        block_sorted = json.dumps(block, sort_keys=True).encode()\n        return hashlib.sha256(block_sorted).hexdigest()\n\n    @property\n    def last_block(self):\n        return self.blockchain[-1]\n        \n    def pow(self, last_proof):\n        \"\"\"\n        Simple PoW Algorithm:\n         - Find a number y, so that hash(xy) starts with 5 zeroes. x is the last y aka last_proof. y is then the new proof.\n        :param last_proof: <int>\n        :return: <int>\n        \"\"\"\n        \n        current_proof = 0\n        while self.validate_proof(last_proof, current_proof) is False:\n            current_proof += 1\n\n        return current_proof\n\n    @staticmethod\n    def validate_proof(last_proof, current_proof):\n        \"\"\"\n        Returns, whether the hash of the lastproof and the current_proof contains 5 leading zeroes.\n        :param last_proof: <int> Previous Proof Number\n        :param current_proof: <int> Current Proof Number\n        :return: <bool>\n        \"\"\"\n\n        possible_hash = hashlib.sha256(f'{last_proof}{current_proof}'.encode()).hexdigest()\n        return possible_hash[:5] == \"00000\"\n        \n    def add_node(self, address):\n        \"\"\"\n        Register a new node\n        :param address: <str> This is the new node's address, for example 'http://192.168.1.112:5000'\n        :return: None\n        \"\"\"\n\n        node_url = urlparse(address)\n        self.nodes.add(node_url.netloc)\n        \n    def validate_blockchain(self, test_chain):\n        \"\"\"\n        Evaluate, whether a blockchain is valid\n        :param chain: <list> The blockchain that shall be tested\n        :return: <bool> Returns true if the blockchain is valid\n        \"\"\"\n\n        last_block = test_chain[0]\n        current_index = 1\n\n        while current_index < len(test_chain):\n            block = test_chain[current_index]\n            \n            # Determine, whether the hash is correct\n            if block['previous_hash'] != self.hash(last_block):\n                return False\n\n            # Determine, wheter the proof of work is correct\n            if not self.validate_proof(last_block['proof'], block['proof']):\n                return False\n\n            last_block = block\n            current_index += 1\n\n        return True\n        \n    def resolve(self):\n        \"\"\"\n        This algorithm resolves conflicts between our nodes. It is the consensus algorithm which I mentioned previously.\n        :return: <bool> Returns true, if our chain was substituted with an updated version\n        \"\"\"\n\n        surrounding_nodes = self.nodes\n        updated_chain = None\n\n        # If we follow our consensus algorithm description, we only want blockchains that are longer, than our current chain\n        max_length = len(self.blockchain)\n\n        # Iterate every surrounding nodes in our network through the consensus algorithm, which means checking if the node's blockchain is longer than our current blockchain and valid and set it as our new blockchain and continue checking, as there could be an even longer and valid blockchain.\n        for node_iterator in surrounding_nodes:\n            response = requests.get(f'http://{node_iterator}/blockchain')\n\n            if response.status_code == 200:\n                length = response.json()['length']\n                chain_iterator = response.json()['chain']\n\n                if length > max_length and self.validate_blockchain(chain_iterator):\n                    max_length = length\n                    updated_chain = chain_iterator\n\n        # If we found a new blockchain, replace our current blockchain with the new one\n        if updated_chain:\n            self.blockchain = updated_chain\n            return True\n\n        return False\n\napp = Flask(__name__)\nnode_identifier = str(uuid4()).replace('-', '')\n\nmyblockchain = MyBlockChain()\n\[email protected]('/blockchain', methods=['GET'])\ndef get_full_chain():\n    output = {\n        'chain': myblockchain.blockchain,\n        'length': len(myblockchain.blockchain),\n    }\n    return jsonify(output), 200\n\[email protected]('/mining', methods=['GET'])\ndef mining():\n    # Calculate the new proof by using our PoW algorithm\n    last_block = myblockchain.last_block\n    last_proof = last_block['proof']\n    proof = myblockchain.pow(last_proof)\n\n    # For finding/mining the proof, the miner is granted a reward\n    # The sender is nobody, as this coin is coming out of the void\n    myblockchain.create_new_transaction(\n        sender=\"0\",\n        recipient=node_identifier,\n        amount=1,\n    )\n\n    # Add the new created block to the chain\n    previous_hash = myblockchain.hash(last_block)\n    newblock = myblockchain.create_new_block(proof, previous_hash)\n\n    output = {\n        'message': \"A new block was mined\",\n        'index': newblock['index'],\n        'transactions': newblock['transactions'],\n        'proof': newblock['proof'],\n        'previous_hash': newblock['previous_hash'],\n    }\n    return jsonify(output), 200\n    \[email protected]('/transactions/add', methods=['POST'])\ndef add_transaction():\n    values = request.get_json()\n\n    # The POST request has to have the following required fields\n    required = ['sender', 'recipient', 'amount']\n    if not all(k in values for k in required):\n        return 'There are values missing', 400\n\n    # Adds a new transaction by utilizing our function\n    index = myblockchain.create_new_transaction(values['sender'], values['recipient'], values['amount'])\n\n    output = {'message': f'Your registered Transaction is going to be a part of the block with the index of {index}'}\n    return jsonify(output), 201\n    \[email protected]('/nodes/add', methods=['POST'])\ndef add_nodes():\n    values = request.get_json()\n\n    nodes = values.get('nodes')\n    if nodes is None:\n        return \"You didn't post a valid list of nodes. Please double check your input!\", 400\n\n    for node in nodes:\n        myblockchain.add_node(node)\n\n    response = {\n        'message': 'All of your specified nodes have been added to the network!',\n        'total_nodes': list(myblockchain.nodes),\n    }\n    return jsonify(response), 201\n\n\[email protected]('/nodes/resolve', methods=['GET'])\ndef consensus():\n    replaced = myblockchain.resolve()\n\n    if replaced:\n        response = {\n            'message': 'There was a longer valid chain within the network. The blockchain of this node has been replaced.',\n            'new_chain': myblockchain.blockchain\n        }\n    else:\n        response = {\n            'message': 'The blockchain of this node is already the longest valid chain within the network.',\n            'chain': myblockchain.blockchain\n        }\n\n    return jsonify(response), 200\n\nif __name__ == '__main__':\n    app.run(host='0.0.0.0', port=5000)\n```\n# Final thoughts\nAnd there you have it!\nYour very own blockchain. Wasn't very hard, was it?\nI sincerely hope you had fun thorughout this tutorial and were able to understand the concept and system behind it better. If you have any questions, please ask them in the comments and I'll try my best to answer them.\n# The obligatory begging\nAs this whole tutorial took me over 2 days to finish, I would love to see a lot of comments and feedback under this post. Also if you find any typos, grammar mistakes, etc. and care to tell me, i would be mor than happy about it, as English is not my native language. So please excuse any mistakes I made. I tried my very best.\nOf course please upvote, if you worship my effort to enrich the community, and if you want to see more such content, consider following me. \nI wish you only the best - See ya!",
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dustvoicereplied to @hursh / re-hursh-7hpiuf-free-re-steem-to-all-my-steemit-friends-20180106t140259089z

2018/01/06 14:03:00 UTC

18,742,169|49d8a6c

author	dustvoice
body	Mine is an interesting article too: https://steemit.com/steemit/@dustvoice/create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required
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fitinfunupvoted (3.00%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 13:10:48 UTC

18,741,125|f9e3d11

author	dustvoice
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mittymartzupvoted (100.00%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 10:58:36 UTC

18,738,481|d7b153b

author	dustvoice
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voter	mittymartz
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paraalttiredoksupvoted (100.00%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 10:39:09 UTC

18,738,093|ff9e309

author	dustvoice
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voter	paraalttiredoks
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vijaynag6upvoted (100.00%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 08:44:24 UTC

18,735,798|8b4ece4

author	dustvoice
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amit-negiupvoted (100.00%) @dustvoice / create-your-own-blockchain-and-cryptocurrency-understand-blockchains-by-creating-one-in-python-no-knowledge-required

2018/01/06 07:18:36 UTC

18,734,084|008ed48

author	dustvoice
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voter	amit-negi
weight	10000 (100.00%)
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Voting Power100.00%

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