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blockchain.py
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blockchain.py
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import json
import rsa
import hashlib
import time
import math
from transaction import *
from utxopool import UTXOPool
COINBASE_AMT = 25
DEFAULT_DIFFICULTY = 10
DIFFICULTY_RECALC_INTERVAL = 10
TARGET_MINE_TIME = 20
class Blockchain:
def __init__(self):
self.blocks = [Block(None, None, [], 0, DEFAULT_DIFFICULTY)]
self.pool = UTXOPool()
@staticmethod
def validate(blockchain):
# first - check previous hashes
for i in range(len(blockchain.blocks)-1):
if blockchain.blocks[i].hash() != blockchain.blocks[i+1].prevHash:
return False
# second - reconstruct blockchain with txs and coinbase recipients
dummyChain = Blockchain()
dummyChain.blocks[0].timestamp = blockchain.blocks[0].timestamp
for block in blockchain.blocks[1:]:
newBlock = Block(dummyChain.blocks[-1].hash(), [tx.clone() for tx in block.txs][0].txOuts[0].address, [tx.clone() for tx in block.txs], block.nonce, block.difficulty)
newBlock.txs.pop(0)
newBlock.timestamp = block.timestamp
try:
dummyChain.addBlockException(newBlock)
except Exception as e:
print(e)
return False
for i in range(len(blockchain.blocks)-1):
difficulty = blockchain.nextDifficulty(i)
if blockchain.blocks[i+1].satisfiedDifficulty() < difficulty:
print("Difficulty not satisfied")
return False
return True
def addBlockException(self, block):
dummyPool = self.pool.clone()
dummyPool.handleCoinbase(block.txs[0])
# check block hash < difficulty too!!
dummyPool.handleTxs(block.txs[1:])
self.pool = dummyPool
self.blocks.append(block)
@staticmethod
def fromJSON(j):
blockchain = Blockchain()
jsonChain = json.loads(j)
# copy over blocks
newBlocks = []
for block in jsonChain['blocks']:
newBlockTxs = []
for tx in block['txs']:
newBlockTxIns = []
newBlockTxOuts = []
for txIn in tx['txIns']:
newBlockTxIn = TxIn(txIn['prevTxHash'], txIn['prevTxOutIndex'])
newBlockTxIn.signature = eval(txIn['signature'])
newBlockTxIns.append(newBlockTxIn)
for txOut in tx['txOuts']:
if txOut['address'] == None:
newPubKey = None
else:
newPubKey = PubKeyWrapper(rsa.key.PublicKey(txOut['address']['n'], txOut['address']['e']))
newBlockTxOut = TxOut(newPubKey, txOut['value'])
newBlockTxOut.txHash = txOut['txHash']
newBlockTxOut.idx = txOut['idx']
newBlockTxOuts.append(newBlockTxOut)
newBlockTx = Transaction(newBlockTxIns, newBlockTxOuts)
newBlockTx.timestamp = tx['timestamp']
newBlockTxs.append(newBlockTx)
coinbaseRecipientDict = block['txs'][0]['txOuts'][0]['address']
if coinbaseRecipientDict == None:
coinbaseRecipient = None
else:
coinbaseRecipient = PubKeyWrapper(rsa.key.PublicKey(coinbaseRecipientDict['n'], coinbaseRecipientDict['e']))
prevHash = newBlocks[-1].hash() if len(newBlocks) else None
newBlock = Block(prevHash, coinbaseRecipient, newBlockTxs, block['nonce'], block['difficulty'])
# remove duplicate coinbase transaction
newBlock.txs.pop(0)
newBlock.timestamp = block['timestamp']
newBlocks.append(newBlock)
blockchain.blocks = newBlocks
# copy over pool
newPoolTxOuts = []
for txOut in jsonChain['pool']['txOuts']:
if txOut['address'] == None:
newPubKey = None
else:
newPubKey = PubKeyWrapper(rsa.key.PublicKey(txOut['address']['n'], txOut['address']['e']))
newPoolTxOut = TxOut(newPubKey, txOut['value'])
newPoolTxOut.txHash = txOut['txHash']
newPoolTxOut.idx = txOut['idx']
newPoolTxOuts.append(newPoolTxOut)
blockchain.pool.txOuts = newPoolTxOuts
# don't need to remove duplicate genesis block because everything was replaced
return blockchain
def toJSON(self):
def customEncoder(o):
if isinstance(o, bytes):
return repr(o)
return o.__dict__
return json.dumps(self, default=customEncoder, indent=2)
def addBlock(self, block):
try:
dummyPool = self.pool.clone()
dummyPool.handleCoinbase(block.txs[0])
# check block hash < difficulty too!!
dummyPool.handleTxs(block.txs[1:])
self.pool = dummyPool
self.blocks.append(block)
except Exception as e:
print(e)
def nextDifficulty(self, blockIndex = None):
if blockIndex == None:
blockIndex = len(self.blocks)-1
dummyBlocks = self.blocks[:blockIndex+1]
top = dummyBlocks[-1]
if len(dummyBlocks) % DIFFICULTY_RECALC_INTERVAL:
return top.difficulty
i = max(-1 * DIFFICULTY_RECALC_INTERVAL, -len(dummyBlocks))
mineTime = (top.timestamp - dummyBlocks[i].timestamp)/abs(i)
intendedMineTimeMultiplier = TARGET_MINE_TIME/mineTime
return round(top.difficulty + math.log(intendedMineTimeMultiplier, 2))
class Block:
def __init__(self, prevHash, coinbaseRecipient, txs, nonce, difficulty):
self.prevHash = prevHash
self.txs = [tx.clone() for tx in txs]
self.nonce = nonce
self.timestamp = time.time()
self.difficulty = difficulty
coinbase = Transaction([], [TxOut(coinbaseRecipient, COINBASE_AMT)])
self.txs.insert(0, coinbase)
def hash(self):
hasher = hashlib.sha256()
hasher.update((str(self.prevHash)+str([tx.represent() for tx in self.txs])+str(self.nonce)+str(self.difficulty)+str(self.timestamp)).encode('utf-8'))
return hasher.hexdigest()
def satisfiedDifficulty(self):
asBin = bin(int(self.hash(),16))
return 258 - len(asBin)
@staticmethod
def fromJSON():
return Block(None, None, None, None, None)
def toJSON(self):
return ""