简单区块链模型，实现了链式结构，创建区块，添加交易数据，共识算法（POW挖矿），分叉选择，工作量证明，多节点数据一致性，基于Flask框架调用
#!/usr/bin/python
# -*- coding: UTF-8 -*-
import hashlib
import hashlib
import json
from time import time
from uuid import uuid4
import requests
from flask import Flask, jsonify, request
class Blockchain(object):
def __init__(self):
self.current_transactions = []
self.chain = []
# 创建创世区块
self.new_block(previous_hash=1, proof=100)
self.nodes = set()#用于保存网络中节点，自动去除重复节点
def new_block(self, proof, previous_hash=None):#创建新区块
"""
创建一个新的区块到区块链中
:param proof: 由工作证明算法生成的证明
:param previous_hash: (Optional) 前一个区块的 hash 值
:return: 新区块
"""
block = {
'index': len(self.chain) + 1,
'timestamp': time(),
'transactions': self.current_transactions,
'proof': proof,
'previous_hash': previous_hash or self.hash(self.chain[-1]),
}
# 重置当前交易记录
self.current_transactions = []
self.chain.append(block)
return block
def new_transaction(self, sender, recipient, amount,about=''):#创建新交易数据
"""
创建一笔新的交易到下一个被挖掘的区块中
:param sender: 发送人的地址
:param recipient: 接收人的地址
:param amount: 金额
:return: 持有本次交易的区块索引
"""
self.current_transactions.append({
'sender': sender,
'recipient': recipient,
'amount': amount,
'about': about,
})
return self.last_block['index'] + 1
@property
def last_block(self):
return self.chain[-1]
@staticmethod
def hash(block):#区块到hash生成
"""
给一个区块生成 SHA-256 值
:param block: Block
:return:
"""
# 我们必须确保这个字典（区块）是经过排序的，否则我们将会得到不一致的散列
block_string = json.dumps(block, sort_keys=True).encode()
return hashlib.sha256(block_string).hexdigest()
def proof_of_work(self, last_proof):#工作量证明
proof = 0
while self.valid_proof(last_proof, proof) is False:
proof += 1
return proof
@staticmethod
def valid_proof(last_proof, proof):
guess = f'{last_proof}{proof}'.encode()
guess_hash = hashlib.sha256(guess).hexdigest()
return guess_hash[:5] == "00000"
#实现共识算法
def valid_chain(self, chain):#负责检查一个链是否有效，方法是遍历每个块并验证散列和证明
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):#是一个遍历我们所有邻居节点的方法，下载它们的链并使用上面的方法验证它们。 如果找到一个长度大于我们的有效链条，我们就取代我们的链条。
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 = Flask(__name__)
# 为这个节点生成一个全球唯一的地址
node_identifier = str(uuid4()).replace('-', '')
# 实例化 Blockchain类
blockchain = Blockchain()
@app.route('/mine', methods=['GET'])
def mine():
last_block = blockchain.last_block
last_proof = last_block['proof']
proof = blockchain.proof_of_work(last_proof)#上一个区块链的proof，难度
#添加默认交易数据
# blockchain.new_transaction(
# sender="0",
# recipient=node_identifier,
# amount=1,
# )
previous_hash = blockchain.hash(last_block)#计算上一个区块的hash
block = blockchain.new_block(proof, previous_hash)
response = {
'message': "New Block Forged",
'index': block['index'],
'transactions': block['transactions'],
'proof': block['proof'],
'previous_hash': block['previous_hash'],
}
return jsonify(response), 200
@app.route('/transactions/new', methods=['POST'])
def new_transaction():
values = request.get_json()
required = ['sender', 'recipient', 'amount','about']
if not all(k in values for k in required):
return 'Missing values', 400
index = blockchain.new_transaction(values['sender'], values['recipient'], values['amount'],values['about'])
response = {'message': f'Transaction will be added to Block {index}'}
return jsonify(response), 201
@app.route('/chain', methods=['GET'])#获取整个区块
def full_chain():
response = {
'chain': blockchain.chain,
'length': len(blockchain.chain),
}
return jsonify(response), 200
@app.route('/nodes/register', methods=['POST'])#http节点注册
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
if __name__ == '__main__':
app.run(host='0.0.0.0', port=5000)