Python从零开始创建区块链

pip install Flask==0.12.2 requests==2.18.4

class Blockchain(object):
 def __init__(self):
  self.chain = []
  self.current_transactions = []
  
 def new_block(self):
  # Creates a new Block and adds it to the chain
  pass
 
 def new_transaction(self):
  # Adds a new transaction to the list of transactions
  pass
 
 @staticmethod
 def hash(block):
  # Hashes a Block
  pass

 @property
 def last_block(self):
  # Returns the last Block in the chain
  pass

block = {
 'index': 1,
 'timestamp': 1506057125.900785,
 'transactions': [
  {
   'sender': "8527147fe1f5426f9dd545de4b27ee00",
   'recipient': "a77f5cdfa2934df3954a5c7c7da5df1f",
   'amount': 5,
  }
 ],
 'proof': 324984774000,
 'previous_hash': "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
}

class Blockchain(object):
 ...
 
 def new_transaction(self, sender, recipient, amount):
  """
  生成新交易信息，信息将加入到下一个待挖的区块中
  :param sender: <str> Address of the Sender
  :param recipient: <str> Address of the Recipient
  :param amount: <int> Amount
  :return: <int> The index of the Block that will hold this transaction
  """

  self.current_transactions.append({
   'sender': sender,
   'recipient': recipient,
   'amount': amount,
  })

  return self.last_block['index'] + 1

import hashlib
import json
from time import time


class Blockchain(object):
 def __init__(self):
  self.current_transactions = []
  self.chain = []

  # Create the genesis block
  self.new_block(previous_hash=1, proof=100)

 def new_block(self, proof, previous_hash=None):
  """
  生成新块
  :param proof: <int> The proof given by the Proof of Work algorithm
  :param previous_hash: (Optional) <str> Hash of previous Block
  :return: <dict> New Block
  """

  block = {
   'index': len(self.chain) + 1,
   'timestamp': time(),
   'transactions': self.current_transactions,
   'proof': proof,
   'previous_hash': previous_hash or self.hash(self.chain[-1]),
  }

  # Reset the current list of transactions
  self.current_transactions = []

  self.chain.append(block)
  return block

 def new_transaction(self, sender, recipient, amount):
  """
  生成新交易信息，信息将加入到下一个待挖的区块中
  :param sender: <str> Address of the Sender
  :param recipient: <str> Address of the Recipient
  :param amount: <int> Amount
  :return: <int> The index of the Block that will hold this transaction
  """
  self.current_transactions.append({
   'sender': sender,
   'recipient': recipient,
   'amount': amount,
  })

  return self.last_block['index'] + 1

 @property
 def last_block(self):
  return self.chain[-1]

 @staticmethod
 def hash(block):
  """
  生成块的 SHA-256 hash值
  :param block: <dict> Block
  :return: <str>
  """

  # We must make sure that the Dictionary is Ordered, or we'll have inconsistent hashes
  block_string = json.dumps(block, sort_keys=True).encode()
  return hashlib.sha256(block_string).hexdigest()

from hashlib import sha256
x = 5
y = 0 # y未知
while sha256(f'{x*y}'.encode()).hexdigest()[-1] != "0":
 y += 1
print(f'The solution is y = {y}')

hash(5 * 21) = 1253e9373e...5e3600155e860

import hashlib
import json

from time import time
from uuid import uuid4


class Blockchain(object):
 ...
  
 def proof_of_work(self, last_proof):
  """
  简单的工作量证明:
   - 查找一个 p' 使得 hash(pp') 以4个0开头
   - p 是上一个块的证明, p' 是当前的证明
  :param last_proof: <int>
  :return: <int>
  """

  proof = 0
  while self.valid_proof(last_proof, proof) is False:
   proof += 1

  return proof

 @staticmethod
 def valid_proof(last_proof, proof):
  """
  验证证明: 是否hash(last_proof, proof)以4个0开头?
  :param last_proof: <int> Previous Proof
  :param proof: <int> Current Proof
  :return: <bool> True if correct, False if not.
  """

  guess = f'{last_proof}{proof}'.encode()
  guess_hash = hashlib.sha256(guess).hexdigest()
  return guess_hash[:4] == "0000"

import hashlib
import json
from textwrap import dedent
from time import time
from uuid import uuid4

from flask import Flask


class Blockchain(object):
 ...


# Instantiate our Node
app = Flask(__name__)

# Generate a globally unique address for this node
node_identifier = str(uuid4()).replace('-', '')

# Instantiate the Blockchain
blockchain = Blockchain()


@app.route('/mine', methods=['GET'])
def mine():
 return "We'll mine a new Block"
 
@app.route('/transactions/new', methods=['POST'])
def new_transaction():
 return "We'll add a new transaction"

@app.route('/chain', methods=['GET'])
def full_chain():
 response = {
  'chain': blockchain.chain,
  'length': len(blockchain.chain),
 }
 return jsonify(response), 200

if __name__ == '__main__':
 app.run(host='0.0.0.0', port=5000)

{
 "sender": "my address",
 "recipient": "someone else's address",
 "amount": 5
}

import hashlib
import json
from textwrap import dedent
from time import time
from uuid import uuid4

from flask import Flask, jsonify, request

...

@app.route('/transactions/new', methods=['POST'])
def new_transaction():
 values = request.get_json()

 # Check that the required fields are in the POST'ed data
 required = ['sender', 'recipient', 'amount']
 if not all(k in values for k in required):
  return 'Missing values', 400

 # Create a new Transaction
 index = blockchain.new_transaction(values['sender'], values['recipient'], values['amount'])

 response = {'message': f'Transaction will be added to Block {index}'}
 return jsonify(response), 201

import hashlib
import json

from time import time
from uuid import uuid4

from flask import Flask, jsonify, request

...

@app.route('/mine', methods=['GET'])
def mine():
 # We run the proof of work algorithm to get the next proof...
 last_block = blockchain.last_block
 last_proof = last_block['proof']
 proof = blockchain.proof_of_work(last_proof)

 # 给工作量证明的节点提供奖励.
 # 发送者为 "0" 表明是新挖出的币
 blockchain.new_transaction(
  sender="0",
  recipient=node_identifier,
  amount=1,
 )

 # Forge the new Block by adding it to the chain
 block = blockchain.new_block(proof)

 response = {
  'message': "New Block Forged",
  'index': block['index'],
  'transactions': block['transactions'],
  'proof': block['proof'],
  'previous_hash': block['previous_hash'],
 }
 return jsonify(response), 200

$ python blockchain.py
* Runing on http://127.0.0.1:5000/ (Press CTRL+C to quit)

$ curl -X POST -H "Content-Type: application/json" -d '{
 "sender": "d4ee26eee15148ee92c6cd394edd974e",
 "recipient": "someone-other-address",
 "amount": 5
}' "http://localhost:5000/transactions/new"

{
 "chain": [
 {
  "index": 1,
  "previous_hash": 1,
  "proof": 100,
  "timestamp": 1506280650.770839,
  "transactions": []
 },
 {
  "index": 2,
  "previous_hash": "c099bc...bfb7",
  "proof": 35293,
  "timestamp": 1506280664.717925,
  "transactions": [
  {
   "amount": 1,
   "recipient": "8bbcb347e0634905b0cac7955bae152b",
   "sender": "0"
  }
  ]
 },
 {
  "index": 3,
  "previous_hash": "eff91a...10f2",
  "proof": 35089,
  "timestamp": 1506280666.1086972,
  "transactions": [
  {
   "amount": 1,
   "recipient": "8bbcb347e0634905b0cac7955bae152b",
   "sender": "0"
  }
  ]
 }
 ],
 "length": 3
}

...
from urllib.parse import urlparse
...


class Blockchain(object):
 def __init__(self):
  ...
  self.nodes = set()
  ...

 def register_node(self, address):
  """
  Add a new node to the list of nodes
  :param address: <str> Address of node. Eg. 'http://192.168.0.5:5000'
  :return: None
  """

  parsed_url = urlparse(address)
  self.nodes.add(parsed_url.netloc)

...
import requests


class Blockchain(object)
 ...
 
 def valid_chain(self, chain):
  """
  Determine if a given blockchain is valid
  :param chain: <list> A blockchain
  :return: <bool> True if valid, False if not
  """

  last_block = chain[0]
  current_index = 1

  while current_index < len(chain):
   block = chain[current_index]
   print(f'{last_block}')
   print(f'{block}')
   print("\n-----------\n")
   # Check that the hash of the block is correct
   if block['previous_hash'] != self.hash(last_block):
    return False

   # Check that the Proof of Work is correct
   if not self.valid_proof(last_block['proof'], block['proof']):
    return False

   last_block = block
   current_index += 1

  return True

 def resolve_conflicts(self):
  """
  共识算法解决冲突
  使用网络中最长的链.
  :return: <bool> True 如果链被取代, 否则为False
  """

  neighbours = self.nodes
  new_chain = None

  # We're only looking for chains longer than ours
  max_length = len(self.chain)

  # Grab and verify the chains from all the nodes in our network
  for node in neighbours:
   response = requests.get(f'http://{node}/chain')

   if response.status_code == 200:
    length = response.json()['length']
    chain = response.json()['chain']

    # Check if the length is longer and the chain is valid
    if length > max_length and self.valid_chain(chain):
     max_length = length
     new_chain = chain

  # Replace our chain if we discovered a new, valid chain longer than ours
  if new_chain:
   self.chain = new_chain
   return True

  return False

@app.route('/nodes/register', methods=['POST'])
def register_nodes():
 values = request.get_json()

 nodes = values.get('nodes')
 if nodes is None:
  return "Error: Please supply a valid list of nodes", 400

 for node in nodes:
  blockchain.register_node(node)

 response = {
  'message': 'New nodes have been added',
  'total_nodes': list(blockchain.nodes),
 }
 return jsonify(response), 201


@app.route('/nodes/resolve', methods=['GET'])
def consensus():
 replaced = blockchain.resolve_conflicts()

 if replaced:
  response = {
   'message': 'Our chain was replaced',
   'new_chain': blockchain.chain
  }
 else:
  response = {
   'message': 'Our chain is authoritative',
   'chain': blockchain.chain
  }

 return jsonify(response), 200

pipenv run python blockchain.py
pipenv run python blockchain.py -p 5001