程式語言：Python3.6+
功能：簡單實現區塊鏈
簡單來說
這幾乎是不可能的，除非計算力超過整體網路的 50%，但與其這麼辛苦倒不如乖乖的挖礦獲利
- Package：
- requests
- flask
- json
- time
- uuid
- urllib
功能：簡單實現區塊鏈
簡單來說
- 區塊鏈就是由無數的區塊(帳本)所組成的，而區塊(帳本)中有著一定數目的交易
- 區塊(帳本)之間則是由 hash 所串連起來
每一個區塊(帳本)都會記錄著前一個區塊(帳本)的 hash 值，並依此產生該區塊(帳本)的 hash 值 - hash 值有指定格式，俗稱挖礦
例如：再加上某個值後，hash 的前四位需為零，也就是 0000...，隨著 0 的數量上升，所需的計算量會大增 - 最正確的區塊鏈則是最長的那個，因為耗費的計算力最大
這幾乎是不可能的，除非計算力超過整體網路的 50%，但與其這麼辛苦倒不如乖乖的挖礦獲利
使用方法
建立節點
目前的區塊鏈
新增交易(POST)，在此用 curl 實現 POST
新增區塊
註冊節點(POST)，在此用 curl 實現 POST
同步區塊鏈
# 可看到相關參數 python web.py -h # 建立指令 python web.py python web.py -P 5000 python web.py -H 127.0.0.1 -P 5000
目前的區塊鏈
http://127.0.0.1:5000/chain
新增交易(POST)，在此用 curl 實現 POST
curl http://127.0.0.1:5000/transactions/new -X POST -H "Content-Type: application/json" -d '{"sender": "d4ee26eee15148ee92c6cd394edd974e", "recipient": "someone-other-address", "amount": 5}'
# windows 需改為
curl http://127.0.0.1:5000/transactions/new -X POST -H "Content-Type: application/json" -d "{\"sender\": \"d4ee26eee15148ee92c6cd394edd974e\", \"recipient\": \"someone-other-address\", \"amount\": 5}"
新增區塊
http://127.0.0.1:5000/mine
註冊節點(POST)，在此用 curl 實現 POST
curl http://127.0.0.1:5000/nodes/register -X POST -H "Content-Type: application/json" -d '{"nodes": ["http://127.0.0.1:5001"]}'
# windows 需改為
curl http://127.0.0.1:5000/nodes/register -X POST -H "Content-Type: application/json" -d "{\"nodes\": [\"http://127.0.0.1:5001\"]}"
同步區塊鏈
# 先建立新的節點
python web.py -H 127.0.0.1 -P 5001
# 觀看目前的狀況
http://127.0.0.1:5001/chain
# 註冊已存在節點
curl http://127.0.0.1:5001/nodes/register -X POST -H "Content-Type: application/json" -d "{\"nodes\": [\"http://127.0.0.1:5000\"]}"
# 同步
http://127.0.0.1:5001/nodes/resolve
程式碼
web.py
from flask import Flask, jsonify, request
from uuid import uuid4
from blockchain import Blockchain
# 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('/chain', methods=['GET'])
def full_chain():
"""
目前的區塊鏈
"""
response = {
'chain': blockchain.chain,
'length': len(blockchain.chain),
}
return jsonify(response), 200
@app.route('/transactions/new', methods=['POST'])
def new_transaction():
"""
新增交易
"""
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
@app.route('/mine', methods=['GET'])
def mine():
"""
產生新的 block
"""
# 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)
# We must receive a reward for finding the proof.
# The sender is "0" to signify that this node has mined a new coin.
blockchain.new_transaction(
sender="0",
recipient=node_identifier,
amount=1,
)
# Forge the new Block by adding it to the chain
previous_hash = blockchain.hash(last_block)
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('/nodes/register', methods=['POST'])
def register_nodes():
"""
註冊節點，別註冊到自己的
"""
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():
"""
更新成最長的區塊鏈
"""
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__':
from argparse import ArgumentParser
parser = ArgumentParser()
parser.add_argument('-P', '--port', default=5000, type=int, help='port to listen on')
parser.add_argument('-H', '--host', default='127.0.0.1', type=str, help='host to listen on')
args = parser.parse_args()
port = args.port
host = args.host
app.run(host=host, port=port)
blockchain.py
import hashlib
import json
from time import time
import requests
from urllib.parse import urlparse
class Blockchain(object):
def __init__(self):
self.current_transactions = []
self.chain = []
self.nodes = set()
# Create the genesis block
self.new_block(previous_hash=1, proof=100)
def new_block(self, proof, previous_hash=None):
"""
Create a new Block in the Blockchain
: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):
"""
Creates a new transaction to go into the next mined Block
: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):
"""
Creates a SHA-256 hash of a Block
: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()
def proof_of_work(self, last_proof):
"""
Simple Proof of Work Algorithm:
- Find a number p' such that hash(pp') contains leading 4 zeroes
- p is the previous proof, and p' is the new proof
: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):
"""
Validates the Proof: Does hash(last_proof, proof) contain 4 leading zeroes?
: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"
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)
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):
"""
This is our Consensus Algorithm, it resolves conflicts
by replacing our chain with the longest one in the network.
:return: <bool> True if our chain was replaced, False if not
"""
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
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