使用Python创建简单的区块链
区块链是带有时间戳的分散式固定记录系列，其中包含任何大小的数据，由分散在全球各地且不属于单个组织的大型计算机网络控制。每个块都使用散列技术进行保护并相互连接，以防止未经授权的人对其进行篡改。
使用Python创建区块链，挖掘新区块，并展示整个区块链：
- 数据将以 JSON 格式存储，该格式非常易于实现且易于阅读。数据存储在一个块中，该块包含多个数据。每分钟都会添加多个块，为了区分一个块，我们将使用指纹识别。
- 指纹是通过使用散列完成的，特别是我们将使用 SHA256 散列算法。每个块都将包含自己的哈希以及前一个函数的哈希，因此它不会被篡改。
- 该指纹将用于将块链接在一起。每个块都将附加到具有其散列的前一个块，并通过提供其散列附加到下一个块。
- 新区块的挖掘是通过成功找到工作证明的答案来完成的。为了使采矿变得困难，工作证明必须足够困难才能被利用。
- 成功挖掘区块后，该区块将被添加到链中。
- 在挖掘多个区块后，必须检查链的有效性，以防止对区块链进行任何形式的篡改。
- 然后将使用Flask制作 Web 应用程序，并根据用户的需要在本地或公开部署。
Python3
# Python program to create Blockchain
# For timestamp
import datetime
# Calculating the hash
# in order to add digital
# fingerprints to the blocks
import hashlib
# To store data
# in our blockchain
import JSON
# Flask is for creating the web
# app and jsonify is for
# displaying the blockchain
from flask import Flask, jsonify
class Blockchain:
# This function is created
# to create the very first
# block and set its hash to "0"
def __init__(self):
self.chain = []
self.create_block(proof=1, previous_hash='0')
# This function is created
# to add further blocks
# into the chain
def create_block(self, proof, previous_hash):
block = {'index': len(self.chain) + 1,
'timestamp': str(datetime.datetime.now()),
'proof': proof,
'previous_hash': previous_hash}
self.chain.append(block)
return block
# This function is created
# to display the previous block
def print_previous_block(self):
return self.chain[-1]
# This is the function for proof of work
# and used to successfully mine the block
def proof_of_work(self, previous_proof):
new_proof = 1
check_proof = False
while check_proof is False:
hash_operation = hashlib.sha256(
str(new_proof**2 - previous_proof**2).encode()).hexdigest()
if hash_operation[:5] == '00000':
check_proof = True
else:
new_proof += 1
return new_proof
def hash(self, block):
encoded_block = json.dumps(block, sort_keys=True).encode()
return hashlib.sha256(encoded_block).hexdigest()
def chain_valid(self, chain):
previous_block = chain[0]
block_index = 1
while block_index < len(chain):
block = chain[block_index]
if block['previous_hash'] != self.hash(previous_block):
return False
previous_proof = previous_block['proof']
proof = block['proof']
hash_operation = hashlib.sha256(
str(proof**2 - previous_proof**2).encode()).hexdigest()
if hash_operation[:5] != '00000':
return False
previous_block = block
block_index += 1
return True
# Creating the Web
# App using flask
app = Flask(__name__)
# Create the object
# of the class blockchain
blockchain = Blockchain()
# Mining a new block
@app.route('/mine_block', methods=['GET'])
def mine_block():
previous_block = blockchain.print_previous_block()
previous_proof = previous_block['proof']
proof = blockchain.proof_of_work(previous_proof)
previous_hash = blockchain.hash(previous_block)
block = blockchain.create_block(proof, previous_hash)
response = {'message': 'A block is MINED',
'index': block['index'],
'timestamp': block['timestamp'],
'proof': block['proof'],
'previous_hash': block['previous_hash']}
return jsonify(response), 200
# Display blockchain in json format
@app.route('/get_chain', methods=['GET'])
def display_chain():
response = {'chain': blockchain.chain,
'length': len(blockchain.chain)}
return jsonify(response), 200
# Check validity of blockchain
@app.route('/valid', methods=['GET'])
def valid():
valid = blockchain.chain_valid(blockchain.chain)
if valid:
response = {'message': 'The Blockchain is valid.'}
else:
response = {'message': 'The Blockchain is not valid.'}
return jsonify(response), 200
# Run the flask server locally
app.run(host='127.0.0.1', port=5000)输出（mine_block）：
{
"index":2,
"message":"A block is MINED",
"previous_hash":"2d83a826f87415edb31b7e12b35949b9dbf702aee7e383cbab119456847b957c",
"proof":533,
"timestamp":"2020-06-01 22:47:59.309000"
}输出（get_chain）：
{
"chain":[{"index":1,
"previous_hash":"0",
"proof":1,
"timestamp":"2020-06-01 22:47:05.915000"},{"index":2,
"previous_hash":"2d83a826f87415edb31b7e12b35949b9dbf702aee7e383cbab119456847b957c",
"proof":533,
"timestamp":"2020-06-01 22:47:59.309000"}],
"length":2
}输出（有效）：
{"message":"The Blockchain is valid."}