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使用Python以及flask框架实现区块链的创建、工作量证明、共识算法、生成网络节点并一步步运行挖矿检验(文末附项目完整代码)

weixin_44995023 2019-06-15 13:29 51 查看 https://blog.csdn.net/weixin_4

本篇内容对从技术角度来解释区块链,用Python实现简单的区块链系统,进一步认识区块链的结构与原理。

1、前提条件

  • 需要了解下区块链的概念。

    区块链的概念起源于比特币,其本质上是一个去中心化的数据库,是分布式数据存储、点对点传输(P2P)、共识机制、加密算法等计算机技术的新型应用模式(摘自百科)。

  • 需要了解哈希的概念。

    如果对哈希不了解,可以查看知乎的内容,网址如下:
    https://www.zhihu.com/question/26762707

  • 需要了解HTTP的工作原理。

    不懂的话,自行百度或谷歌。

  • 安装支持HTTP协议的客户端

    如Postman或者cURL,其他也可以。

  • 需要安装Python3.6+等文件

    后面的章节"5、编译Python文件"会详细讲解。

  • 源码地址

    [code]https://github.com/dvf/blockchain

2、创建一个区块链

可以用各种文本编辑器或者IDE编写Python程序,比如Subline、EditPlus、PyCharm、VSCode、Atom等。

新建一个目录,暂且命名为"py_blockchain_demo",用于存放要编写的python文件,然后新建一个名为'blockchain.py'的文件。

2.1 描述区块链

创建一个

Blockchain
类 ,构造函数创建了一个初始化的空列表(要存储我们的区块链),并且另一个存储交易。下面是我们这个类的实例:

[code]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

Blockchain
类负责管理链式数据,它会存储交易并且还有添加新的区块到链式数据的Method。让我们开始扩充更多方法。

2.2 区块结构

每个块都有一个

索引
,一个
时间戳(Unix时间戳)
,一个
事务列表
, 一个
校验(稍后详述)
前一个块的散列

下面是一个Block的例子 :

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

在这一点上,一个

区块链
的概念应该是明显的 - 每个新块都包含在其内的前一个块的
散列
。 这是至关重要的,因为这是
区块链
不可改变的原因:如果攻击者损坏
区块链
中较早的块,则所有后续块将包含不正确的哈希值。

这有道理吗? 如果你还没有想通,花点时间仔细思考一下 - 这是区块链背后的核心理念。在学习中有迷茫不知如何学习的朋友小编推荐一个学Python的学习q u n 315 -346-  913可以来了解一起进步一起学习!免费分享视频资料

2.3 添加交易到区块

我们将需要一个添加交易到区块的方式。我们的 new_transaction()方法的责任就是这个,并且它非常的简单:

[code]class Blockchain(object):
...

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

new_transaction()
方法添加了交易到列表,它返回了交易将被添加到的区块的索引---讲开采下一个这对稍后对提交交易的用户有用。

2.4 创建新的区块

当我们的

Blockchain
被实例化后,我们需要将 创世 区块(一个没有前导区块的区块)添加进去进去。我们还需要向我们的起源块添加一个 证明,这是挖矿的结果(或工作证明)。 我们稍后会详细讨论挖矿。

除了在构造函数中创建 创世 区块外,我们还会补全

new_block()
new_transaction()
hash()
函数:

[code]import hashlib
import json
from time import time

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)

def new_block(self, proof, previous_hash=None):
"""
创建一个新的区块到区块链中
:param proof: <int> 由工作证明算法生成的证明
:param previous_hash: (Optional) <str> 前一个区块的 hash 值
:return: <dict> 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):
"""
创建一笔新的交易到下一个被挖掘的区块中
:param sender: <str> 发送人的地址
:param recipient: <str> 接收人的地址
:param amount: <int> 金额
:return: <int> 持有本次交易的区块索引
"""
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):
"""
给一个区块生成 SHA-256 值
:param block: <dict> Block
:return: <str>
"""

# 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(
4000
)

上面的代码应该是直白的 --- 为了让代码清晰,我添加了一些注释和文档说明。 我们差不多完成了我们的区块链。 但在这个时候你一定很疑惑新的块是怎么被创建、锻造或挖掘的。

3、工作量证明算法

3.1 理解工作量证明

使用工作量证明(PoW)算法,来证明是如何在区块链上创建或挖掘新的区块。PoW 的目标是计算出一个符合特定条件的数字,这个数字对于所有人而言必须在计算上非常困难,但易于验证。这是工作证明背后的核心思想。

我们将看到一个简单的例子帮助你理解:

假设一个整数 x 乘以另一个整数 y 的积的 Hash 值必须以 0 结尾,即 hash(x * y) = ac23dc...0。设 x = 5,求 y ?用 Python 实现:

[code]from hashlib import sha256
x = 5
y = 0  # We don't know what y should be yet...
while sha256(f'{x*y}'.encode()).hexdigest()[-1] != "0":
y += 1
print(f'The solution is y = {y}')

结果是: y = 21。因为,生成的 Hash 值结尾必须为 0。

[code]hash(5 * 21) = 1253e9373e...5e3600155e860

在比特币中,工作量证明算法被称为 Hashcash ,它和上面的问题很相似,只不过计算难度非常大。这就是矿工们为了争夺创建区块的权利而争相计算的问题。 通常,计算难度与目标字符串需要满足的特定字符的数量成正比,矿工算出结果后,就会获得一定数量的比特币奖励(通过交易)。

验证结果,当然非常容易。

3.2 实现工作量证明

让我们来实现一个相似 PoW 算法。规则类似上面的例子:

找到一个数字 P ,使得它与前一个区块的 proof 拼接成的字符串的 Hash 值以 4 个零开头。

[code]import hashlib
import json

from time import time
from uuid import uuid4

class Blockchain(object):
...

def proof_of_work(self, last_proof):
"""
Simple Proof of Work Algorithm:
- Find a number p' such that hash(pp') contains leading 4 zeroes, where p is the previous p'
- 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"

衡量算法复杂度的办法是修改零开头的个数。使用 4 个来用于演示,你会发现多一个零都会大大增加计算出结果所需的时间。

现在 Blockchain 类基本已经完成了,接下来使用 HTTP requests 来进行交互。

4、Blockchain 作为 API 接口

我们将使用 Python Flask 框架,这是一个轻量 Web 应用框架,它方便将网络请求映射到 Python 函数,现在我们来让 Blockchain 运行在基于 Flask web 上。

我们将创建三个接口:

  • /transactions/new : 创建一个交易并添加到区块
  • /mine :告诉服务器去挖掘新的区块
  • /chain :返回整个区块链

4.1 创建节点

我们的“Flask 服务器”将扮演区块链网络中的一个节点。我们先添加一些框架代码:

[code]import hashlib
import json
from textwrap import dedent
from time import time
from uuid import uuid4

from flask import Flask

class Blockchain(object):
...

# 实例化节点
app = Flask(__name__)

# 为此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()

# 创建 /mine 接口,GET 方式请求
@app.route('/mine', methods=['GET'])
def mine():
return "We'll mine a new Block"

# 创建 /transactions/new 接口,POST 方式请求,可以给接口发送交易数据
@app.route('/transactions/new', methods=['POST'])
def new_transaction():
return "We'll add a new transaction"

# 创建 /chain 接口,返回整个区块链
@app.route('/chain', methods=['GET'])
def full_chain():
response = {
'chain': blockchain.chain,
'length': len(blockchain.chain),
}
return jsonify(response), 200

# 服务器运行端口 5000
if __name__ == '__main__':
app.run(host='0.0.0.0', port=5000)

4.2 发送交易

发送到节点的交易数据结构如下:

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

因为我们已经有了添加交易的方法,所以基于接口来添加交易就很简单了。让我们为添加事务写函数:

[code]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

4.3 挖矿

挖矿正是神奇所在,它很简单,做了一下三件事:

1.计算工作量证明 PoW
2.通过新增一个交易授予矿工(自己)一个币
3.构造新区块并将其添加到链中

[code]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)

# 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

注意交易的接收者是我们自己的服务器节点,我们做的大部分工作都只是围绕 Blockchain 类方法进行交互。到此,我们的区块链就算完成了,我们来实际运行下。

5、编译Python文件

在Mac上编译Python3这里有点麻烦,特别说明一下。

5.1 Mac安装Python3

Python之所以强大,其中一个原因是其丰富的第三方库。pip则是python第三方库的包管理工具。
由于在Mac上python2和python3是共存的。因而python3对应的包管理工具的命令就是pip3。

如果通过Homebrew安装python3,那么pip3会同时安装。所以建议直接通过homebrew安装python3。

[code]# 安装Python3
brew install python3
# 检查Python3版本(即检查是否安装成功)
python3 -V

5.2 安装Pipenv

Python版本众多,在开发中经常需要使用不同版本的Python,不同项目也可能会使用不同版本的第三方库,这是我们就需要搭建多个Python虚拟环境。pipenv为官方推荐工具,使Python虚拟环境更加方便。

[code]# 安装pipenv
pip3 install pipenv

5.3 创建Python虚拟环境

进入到Python文件所在目录,依次执行如下命令

[code]# 创建Python虚拟环境,并指定Python版本
pipenv --python=python3.6
# 安装Flask、requests模块
pipenv install Flask==0.12.2 requests==2.18.4

6、运行区块链

可以使用 cURL 或 Postman 去和 API 进行交互。
用pipenv指定端口号(代码中默认端口为5000,可以省略后面的"-p 5000"),并启动Sever:

[code]pipenv run python blockchain.py -p 5000

终端显示如下:

[code]wenzildeiMac:py_blockchain_demo wenzil$ pipenv run python blockchain.py -p 5000
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

让我们通过请求 http://localhost:5000/mine (GET)来进行挖矿:

挖矿

 

用 Postman 发起一个 GET 请求。

创建一个交易请求,请求 http://localhost:5000/transactions/new (POST),如图:

创建一个请求交易

"Headers"中添加这样的Key-Value,返回会报服务器错误"500 Internal Server Error"。

[code]'content-type':'application/json'

如果不是使用 Postman,则用一下的 cURL 语句也是一样的:

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

提交了两次请求后,需要挖矿(也就是请求"mine"接口)使交易生效。

 

再次挖矿使交易生效

这时,再通过请求 http://localhost:5000/chain 可以得到所有的块信息。

[code]{
"chain": [
{
"index": 1,
"previous_hash": "1",
"proof": 100,
"timestamp": 1528705939.274652,
"transactions": []
},
{
"index": 2,
"previous_hash": "22efcab1c2990f7d371e5159fe9f753ea4f5b0f9b173f0e41004eb1b6efcd1f7",
"proof": 24960,
"timestamp": 1528705943.739656,
"transactions": [
{
"amount": 1,
"recipient": "2aaa370d7d604b708678a510f11da5d7",
"sender": "0"
}
]
},
{
"index": 3,
"previous_hash": "0cfdac7a19302f5d3af7d20ebf7997afadd88b5f4f937ade867c24701fc21158",
"proof": 9425,
"timestamp": 1528706168.36694,
"transactions": [
{
"amount": 5,
"recipient": "someone-other-address",
"sender": "d4ee26eee15148ee92c6cd394edd974e"
},
{
"amount": 5,
"recipient": "someone-other-address",
"sender": "d4ee26eee15148ee92c6cd394edd974e"
},
{
"amount": 1,
"recipient": "2aaa370d7d604b708678a510f11da5d7",
"sender": "0"
}
]
}
],
"length": 3
}

7、一致性(共识)

我们已经有了一个基本的区块链可以接受交易和挖矿。但是区块链系统应该是分布式的。既然是分布式的,那么我们究竟拿什么保证所有节点有同样的链呢?这就是一致性问题,我们要想在网络上有多个节点,就必须实现一个一致性的算法

7.1 注册节点

在实现一致性算法之前,我们需要找到一种方式让一个节点知道它相邻的节点。每个节点都需要保存一份包含网络中其它节点的记录。因此让我们新增几个接口:

1、/nodes/register : 接收 URL 形式的新节点列表.
2、/nodes/resolve :执行一致性算法,解决任何冲突,确保节点拥有正确的链.
我们修改下 Blockchain 的 init 函数并提供一个注册节点方法:

[code]...
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)

我们用 set 来储存节点,这是一种避免重复添加节点的简单方法。

7.2 实现共识算法

就像先前讲的那样,当一个节点与另一个节点有不同的链时,就会产生冲突。 为了解决这个问题,我们将制定最长的有效链条是最权威的规则。换句话说就是:在这个网络里最长的链就是最权威的。 我们将使用这个算法,在网络中的节点之间达成共识。

[code]...
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):
"""
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, v
1b023
alid chain longer than ours
if new_chain:
self.chain = new_chain
return True

return False

第一个方法

valid_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。

resolve_conflicts()
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。

我们将两个端点注册到我们的API中,一个用于添加相邻节点,另一个用于解决冲突:

[code]@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

在这一点上,如果你喜欢,你可以使用一台不同的机器,并在你的网络上启动不同的节点。 或者使用同一台机器上的不同端口启动进程。 我在我的机器上,不同的端口上创建了另一个节点,并将其注册到当前节点。 因此,我有两个节点:

http://localhost:5000
http://localhost:5001

注册一个新节点

 

然后我在节点 2 上挖掘了一些新的块,以确保链条更长。 之后,我在节点1上调用 GET /nodes/resolve,其中区块链数据由一致性算法取代(注:这一步运行结果跟原文有点出入,可以查看原文的结果):

 

验证节点

这是一个包,去找一些朋友一起,以帮助测试你的区块链。

最终完整Python源代码如下:

[code]import hashlib
import json
from time import time
from urllib.parse import urlparse
from uuid import uuid4

import requests
from flask import Flask, jsonify, request

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

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

def register_node(self, address):
"""
Add a new node to the list of nodes
:param address: Address of node. Eg. 'http://192.168.0.5:5000'
"""

parsed_url = urlparse(address)
if parsed_url.netloc:
self.nodes.add(parsed_url.netloc)
elif parsed_url.path:
# Accepts an URL without scheme like '192.168.0.5:5000'.
self.nodes.add(parsed_url.path)
else:
raise ValueError('Invalid URL')

def valid_chain(self, chain):
"""
Determine if a given blockchain is valid
:param chain: A blockchain
:return: 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
last_block_hash = self.hash(last_block)
if block['previous_hash'] != last_block_hash:
return False

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

def new_block(self, proof, previous_hash):
"""
Create a new Block in the Blockchain
:param proof: The proof given by the Proof of Work algorithm
:param previous_hash: Hash of previous Block
:return: 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: Address of the Sender
:param recipient: Address of the Recipient
:param amount: Amount
:return: 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: Block
"""

# 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_block):
"""
Simple Proof of Work Algorithm:
- Find a number p' such that hash(pp') contains leading 4 zeroes
- Where p is the previous proof, and p' is the new proof

:param last_block: <dict> last Block
:return: <int>
"""

last_proof = last_block['proof']
last_hash = self.hash(last_block)

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

return proof

@staticmethod
def valid_proof(last_proof, proof, last_hash):
"""
Validates the Proof
:param last_proof: <int> Previous Proof
:param proof: <int> Current Proof
:param last_hash: <str> The hash of the Previous Block
:return: <bool> True if correct, False if not.
"""

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

# Instantiate the 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():
# We run the proof of work algorithm to get the next proof...
last_block = blockchain.last_block
proof = blockchain.proof_of_work(last_block)

# 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('/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

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

@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

if __name__ == '__main__':
from argparse import ArgumentParser

parser = ArgumentParser()
parser.add_argument('-p', '--port', default=5000, type=int, help='port to listen on')
args = parser.parse_args()
port = args.port

app.run(host='0.0.0.0', port=port)



 

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