目錄

背景

比特幣從誕生到現(xiàn)在已經(jīng)10年了,最近一段時(shí)間因?yàn)楣ぷ髟蚪佑|到了區(qū)塊鏈相關(guān)的技術(shù),為了揭開其背后的神秘面紗,我們就從頭開始構(gòu)建一個(gè)簡(jiǎn)單的區(qū)塊鏈。在行動(dòng)之前我們先看一下比特幣的整體結(jié)構(gòu).

比特幣內(nèi)部結(jié)構(gòu)

可以看到比特幣主要有四個(gè)部分

previous hash(前一個(gè)區(qū)塊的hash)

merkle root(默克爾樹根節(jié)點(diǎn),內(nèi)部存儲(chǔ)交易數(shù)據(jù))

timestamp(當(dāng)前區(qū)塊生成的時(shí)間)

nonce(曠工計(jì)算hash值次數(shù))

transaction_structure.png

我們實(shí)現(xiàn)的區(qū)塊鏈數(shù)據(jù)結(jié)構(gòu)(簡(jiǎn)單實(shí)現(xiàn)并不完整)

index 當(dāng)前第幾個(gè)區(qū)塊

timestamp 該區(qū)塊創(chuàng)建時(shí)的時(shí)間戳

data 交易信息

previousHash 前一個(gè)區(qū)塊的hash

hash 當(dāng)前區(qū)塊的hash

注意點(diǎn)

第一個(gè)區(qū)塊叫做創(chuàng)世區(qū)塊(genesis block),區(qū)塊鏈創(chuàng)建的時(shí)候默認(rèn)生產(chǎn)的

這里用的是單純的鏈表,不是用默克爾樹存儲(chǔ)

coding

from hashlib import sha256

//區(qū)塊schema

class Block:

def __init__(self,index,timestamp,data,previousHash=""):

self.index = index

self.timestamp = timestamp

self.data = data

self.previousHash = previousHash

self.hash = self.calculateHash()

//計(jì)算當(dāng)前區(qū)塊的hash值

def calculateHash(self):

plainData = str(self.index)+str(self.timestamp)+str(self.data)

return sha256(plainData.encode('utf-8')).hexdigest()

def __str__(self):

return str(self.__dict__)

//區(qū)塊鏈schema

class BlockChain:

//初始化的時(shí)候 創(chuàng)建 創(chuàng)世區(qū)塊

def __init__(self):

self.chain = [self.createGenesisBlock()]

//構(gòu)建創(chuàng)世區(qū)塊

def createGenesisBlock(self):

return Block(0,"01/01/2018","genesis block","0")

//獲取最后一個(gè)區(qū)塊

def getLatestBlock(self):

return self.chain[len(self.chain)-1]

//往區(qū)塊鏈里面添加區(qū)塊

def addBlock(self,newBlock):

newBlock.previousHash = self.getLatestBlock().hash

newBlock.hash = newBlock.calculateHash()

self.chain.append(newBlock)

def __str__(self):

return str(self.__dict__)

//校驗(yàn)區(qū)塊鏈?zhǔn)遣皇怯行У?有沒有人被篡改

def chainIsValid(self):

for index in range(1,len(self.chain)):

currentBlock = self.chain[index]

previousBlock = self.chain[index-1]

if (currentBlock.hash != currentBlock.calculateHash()):

return False

if previousBlock.hash != currentBlock.previousHash:

return False

return True

myCoin = BlockChain()

myCoin.addBlock(Block(1,"02/01/2018","{amount:4}"))

myCoin.addBlock(Block(2,"03/01/2018","{amount:5}"))

#print block info 打印區(qū)塊鏈信息

print("print block info ####:")

for block in myCoin.chain:

print(block)

#check blockchain is valid 檢查區(qū)塊鏈?zhǔn)遣皇怯行У?/p>

print("before tamper block,blockchain is valid ###")

print(myCoin.chainIsValid())

#tamper the blockinfo 篡改區(qū)塊2的數(shù)據(jù)

myCoin.chain[1].data = "{amount:1002}"

print("after tamper block,blockchain is valid ###")

print(myCoin.chainIsValid())

輸出結(jié)果

print block info ####:

{'index': 0, 'timestamp': '01/01/2018', 'data': 'genesis block', 'previousHash': '0', 'hash': 'd8d21e5ba33780d5eb77d09d3b407ceb8ade4e5545ef951de1997b209d91e264'}

{'index': 1, 'timestamp': '02/01/2018', 'data': '{amount:4}', 'previousHash': 'd8d21e5ba33780d5eb77d09d3b407ceb8ade4e5545ef951de1997b209d91e264', 'hash': '15426e32db30f4b26aa719ba5e573f372f41e27e4728eb9e9ab0bea8eae63a9d'}

{'index': 2, 'timestamp': '03/01/2018', 'data': '{amount:5}', 'previousHash': '15426e32db30f4b26aa719ba5e573f372f41e27e4728eb9e9ab0bea8eae63a9d', 'hash': '75119e897f21c769acee6e32abcefc5e88e250a1f35cc95946379436050ac2f0'}

before tamper block,blockchain is valid ###

True

after tamper block,blockchain is valid ###

False

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