Blockchain

Table of Contents

1. BTC: decentralized currency

1.1. 密码学原理

1.1.1. Crypto-Currency

  1. cryptographic hash function: collision resistance
  2. hidding:
  3. digital commitment : digital equivalent of a sealed envelope
  4. puzzle friendly: nonce : H(block header)<= target for all possible

input

  1. difficult to solve but easy to proof.

1.1.2. SAH256 Secure Hash Algorithm

1.1.3. Count

  1. public key : 加密
  2. private key : 解密 : asymmetric encryption algorithm

1.1.4. Merkel Tree

块内的交易以树的形状存放

1.2. 节点

1.2.1. 重节点

only block header

  1. block header

    version hash of previous block header merkel root hash target nonce

1.2.2. 轻节点：Merkel Proof : Merkel Tree

block header block body proof of membership : proof of inclusion

1.3. distributed consensus

1.3.1. FLP impossibility result

asynchronous :faulty

1.3.2. CAP theorem

consistency : Avaliability : Partition tolerance

1.4. fork

1.4.1. state fork

forking attack : 挖矿时同时挖到两个块 deliberate fork :故意制造的

1.4.2. protocd fork

hard fork : software update : block size limit :

2. ETH : decentralized contract

memory hard mining puzzle proof of work -> proof of stake SAIC resistance smart contract

2.1. Patricia Tree

3. python

3.1. part1

import hashlib
import json

class Block():
    def __init__(self, nonce,tstamp, transcation, prevhash=''):
        self.nonce = nonce
        self.tstamp = tstamp
        self.transcation = transcation
        self.prevhash = prevhash
        self.hash =self.calcHash()
    def __str__(self):
        string = 'nonce:'+str(self.nonce)+'\n'
        string += 'tstamp:'+str(self.tstamp)+'\n'
        string += 'transcation:'+str(self.transcation)+'\n'
        string += 'prevhash:'+str(self.prevhash)+'\n'
        string += 'hash:'+str(self.hash)+'\n'
        return string
    def calcHash(self):
        block_string = json.dumps({'nonce':self.nonce, 'tstamp':self.tstamp, 'transcation':self.transcation, 'prevhash':self.prevhash}, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()

class Blockchain():
    def __init__(self):
        self.chain=[self.generateGensisBlock(),]
    def generateGensisBlock(self):
        return Block(0,'Fri Oct 26 21:15:12 2018','Gensis Block')
    def getLastBlock(self):
        return self.chain[-1]
    def addBlock(self,newBlock):
        newBlock.prevhash=self.getLastBlock().hash
        newBlock.hash=newBlock.calcHash()
        self.chain.append(newBlock)
    def isChainValid(self):
        for i in range(1,len(self.chain)):
            prevb = self.chain[i-1]
            currb = self.chain[i]
            if(currb.hash != currb.calcHash()):
                print('invalid block')
                return False
            if(currb.prevhash != prevb.hash):
                print('invalid chain')
                return False
        return True


shangCoin = Blockchain()
shangCoin.addBlock(Block(1,'Fri Oct 26 21:22:51 2018',100))
shangCoin.addBlock(Block(2,'Fri Oct 26 21:23:28 2018',200))

shangCoin.chain[1].transcation = 66
print('only change transcation:'+ '\n'+str(shangCoin.chain[1].calcHash()) +'\n'+ str(shangCoin.chain[1].hash))
#如果只是改了一个transaction的值，在执行calcHash之后的结果肯定不等于之前存在hash属性里的结果一致，会报错
shangCoin.chain[1].hash =shangCoin.chain[1].calcHash()
print('after change transcation, and hash all again:'+'\n'+str(shangCoin.chain[2].prevhash)+'\n'+str(shangCoin.chain[1].hash))
#如果在改变transaction后，再hash整个块，则存在下一个块内的prevhash将不会等于这个块内hash变化后的值

for b in shangCoin.chain:
    print(b)
    print(shangCoin.isChainValid())

3.2. part2

import hashlib
import json

class Block():
    def __init__(self, nonce,tstamp, transcation, prevhash=''):
        self.nonce = nonce
        self.tstamp = tstamp
        self.transcation = transcation
        self.prevhash = prevhash
        self.hash =self.calcHash()
    def __str__(self):
        string = 'nonce:'+str(self.nonce)+'\n'
        string += 'tstamp:'+str(self.tstamp)+'\n'
        string += 'transcation:'+str(self.transcation)+'\n'
        string += 'prevhash:'+str(self.prevhash)+'\n'
        string += 'hash:'+str(self.hash)+'\n'
        return string
    def calcHash(self):
        block_string = json.dumps({'nonce':self.nonce, 'tstamp':self.tstamp, 'transcation':self.transcation, 'prevhash':self.prevhash}, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()
    def mineBlock(self,difficult):
        while(self.hash[:difficult] != str('').zfill(difficult)):
            self.nonce += 1
            self.hash = self.calcHash()
            print('the mineBlock is:',self.hash)

class Blockchain():
    def __init__(self):
        self.chain=[self.generateGensisBlock(),]
        self.difficult = 3
    def generateGensisBlock(self):
        return Block(0,'Fri Oct 26 21:15:12 2018','Gensis Block')
    def getLastBlock(self):
        return self.chain[-1]
    def addBlock(self,newBlock):
        newBlock.prevhash=self.getLastBlock().hash
        newBlock.hash=newBlock.calcHash()
        newBlock.mineBlock(self.difficult)
        self.chain.append(newBlock)
    def isChainValid(self):
        for i in range(1,len(self.chain)):
            prevb = self.chain[i-1]
            currb = self.chain[i]
            if(currb.hash != currb.calcHash()):
                print('invalid block')
                return False
            if(currb.prevhash != prevb.hash):
                print('invalid chain')
                return False
        return True


shangCoin = Blockchain()
print('Adding the first block')
shangCoin.addBlock(Block(1,'Fri Oct 26 21:22:51 2018',100))
print('Adding the second block')
shangCoin.addBlock(Block(2,'Fri Oct 26 21:23:28 2018',200))

# shangCoin.chain[1].transcation = 66
# print('only change transcation:'+ '\n'+str(shangCoin.chain[1].calcHash()) +'\n'+ str(shangCoin.chain[1].hash))
# #如果只是改了一个transaction的值，在执行calcHash之后的结果肯定不等于之前存在hash属性里的结果一致，会报错
# shangCoin.chain[1].hash =shangCoin.chain[1].calcHash()
# print('after change transcation, and hash all again:'+'\n'+str(shangCoin.chain[2].prevhash)+'\n'+str(shangCoin.chain[1].hash))
# #如果在改变transaction后，再hash整个块，则存在下一个块内的prevhash将不会等于这个块内hash变化后的值

for b in shangCoin.chain:
    print(b)

if(shangCoin.isChainValid()):

    print('valid blockchain')
else:
    print('hacked blockchain')

3.3. part3

import hashlib
import json
from datetime import datetime 
class Transaction():
    def __init__(self, from_address,to_address, amount):
        self.from_address = from_address
        self.to_address = to_address
        self.amount = amount

class Block():
    def __init__(self,tstamp, transcationList, prevhash=''):
        self.nonce = 0
        self.tstamp = tstamp
        self.transcationList = transcationList
        self.prevhash = prevhash
        self.hash =self.calcHash()
    def __str__(self):
        string = 'nonce:'+str(self.nonce)+'\n'
        string += 'tstamp:'+str(self.tstamp)+'\n'
        string += 'transcation:'+str(self.transcation)+'\n'
        string += 'prevhash:'+str(self.prevhash)+'\n'
        string += 'hash:'+str(self.hash)+'\n'
        return string
    def calcHash(self):
        block_string = json.dumps({'nonce':self.nonce, 'tstamp':str(self.tstamp), 'transcation':self.transcationList[0].amount, 'prevhash':self.prevhash}, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()
    def mineBlock(self,difficult):
        while(self.hash[:difficult] != str('').zfill(difficult)):
            self.nonce += 1
            self.hash = self.calcHash()
            print('the mineBlock is:',self.hash)

class Blockchain():
    def __init__(self):
        self.chain=[self.generateGensisBlock(),]
        self.difficult = 3
        self.pendingTransactions = []
        self.mining_reward = 100

    def generateGensisBlock(self):
        return Block('Fri Oct 26 21:15:12 2018', [Transaction(None,None,0),])

    def getLastBlock(self):
        return self.chain[-1]

    # def addBlock(self,newBlock):
    #     newBlock.prevhash=self.getLastBlock().hash
    #     newBlock.hash=newBlock.calcHash()
    #     newBlock.mineBlock(self.difficult)
    #     self.chain.append(newBlock)
    def minePendingTranaction(self,mining_reward_address):
        block = Block(datetime.now(), self.pendingTransactions)
        block.mineBlock(self.difficult)
        print('Block is mined to get reward:',self.mining_reward)
        self.chain.append(block)
        self.pendingTransactions = [Transaction(None,mining_reward_address, self.mining_reward)]

    def createTransaction(self,T):
        self.pendingTransactions.append(T)

    def getBalence(self,address):
        balance = 0
        for b in self.chain:
            for t in b.transcationList:
                if t.to_address==address:
                    balance += t.amount
                if t.from_address==address:
                    balance -= t.amount
        return balance

    def isChainValid(self):
        for i in range(1,len(self.chain)):
            prevb = self.chain[i-1]
            currb = self.chain[i]
            if(currb.hash != currb.calcHash()):
                print('invalid block')
                return False
            if(currb.prevhash != prevb.hash):
                print('invalid chain')
                return False
        return True


shangCoin = Blockchain()
shangCoin.createTransaction(Transaction('address1', 'address2',100))
shangCoin.createTransaction(Transaction('address2', 'address1',50))
print('starting mining:')
shangCoin.minePendingTranaction('shangaddress')
print('shangCoin miner balance is:', shangCoin.getBalence('shangaddress'))

shangCoin.createTransaction(Transaction('address1', 'address2',200))
shangCoin.createTransaction(Transaction('address2', 'address1',150))
print('starting mining again:')
shangCoin.minePendingTranaction('shangaddress')
print('shangCoin miner balance is:', shangCoin.getBalence('shangaddress'))

3.4. part4 (has error)

import hashlib
import json
from datetime import datetime 
from flask import Flask
from flask import jsonify
from time import time

class Block():
    def __init__(self, nonce, tstamp, transationList, prevhash='', hash =''):
        self.nonce = nonce
        self.tstamp = tstamp
        self.transationList = transationList
        self.prevhash = prevhash
        if hash == '':
            self.hash = self.calcHash
        else:
            self.hash =hash

    def toDict(self):
        return {'nonce':self.nonce, 'tstamp':str(self.tstamp), 'transation':self.transationList, 'prevhash':self.prevhash, 'hash':self.hash}

    def calcHash(self):
        block_string = json.dumps({'nonce':self.nonce, 'tstamp':str(self.tstamp), 'transation':self.transationList, 'prevhash':self.prevhash}, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()
    def mineBlock(self, difficult):
        while(self.hash[:difficult] != str('').zfill(difficult)):
            self.nonce += 1
            self.hash = self.calcHash()
            print('the mineBlock is:',self.hash)

class Blockchain():
    def __init__(self):
        self.chain=[]
        self.difficult=3
        self.pendingTransations = []
        self.mining_reward = 100
        self.generateGensisBlock()
    def generateGensisBlock(self):
        dect = {'nonce':0, 'tstamp':'Sun Oct 28 12:54:03 2018', 'transationList':[{'from_address':None, 'to_address':None, 'amount':0},],'hash':''}
        b = Block(**dect)
        self.chain.append(b.toDict())

    def getLastBlock(self):
        return Block(**self.chain[-1])

    def minePendingTransation(self, mining_reward_address):
        self.pendingTransations = [{'from_address':None,'to_address':mining_reward_address,'amount':self.mining_reward},]
        block = Block(0, str(datetime.now()),self.pendingTransations)
        block.prevhash = self.getLastBlock().hash
        block.mineBlock(self.difficult)
        print('Block is mined to get reward:',self.mining_reward)
        self.chain.append(block.toDict())

    def createTransation(self, from_address, to_address,amount):
        self.pendingTransations.append({'from_adress':from_address,'to_address':to_address, 'amount':amount})

    def getBalence(self,address):
        balance = 0
        for index in range(len(self.chain)):
            dictList=self.chain[index]['transationList']
            for dic in dictList:
                if dic['to_address']==address:
                    balance += dic['amount']
                if dic['from_address']==address:
                    balance -= dic['amount']
        return balance

    def isChainValid(self):
        for i in range(1,len(self.chain)):
            prevb =Block(**self.chain[i-1])
            currb =Block(**self.chain[i])
            if(currb.hash != currb.calcHash()):
                print('invalid block')
                return False
            if(currb.prevhash != prevb.hash):
                print('invalid chain')
                return False
        return True


shangCoin = Blockchain()
shangCoin.createTransation('address1', 'address2',100)
shangCoin.createTransation('address2', 'address1',50)
print('starting mining:')
shangCoin.minePendingTransation("shangaddress")
print('shangCoin miner balance is:', shangCoin.getBalence("shangaddress"))
print(shangCoin.isChainValid())

Author: si

Created: 2025-01-24 Fr 15:34

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