Proof of work

簡易的なhash計算

import hashlib

input_text = "satoshi"

for nonce in range(20):
    input_data = input_text + str(nonce)
    hash = hashlib.sha256(input_data.encode("UTF-8")).hexdigest()
    print(input_data + " → " + hash)

ブロックヘッダのdifficulty bitsにハッシュ値の条件が書かれている
0x1e777777 のような形式で記述されている。

# difficulty_bits = 0x1e777777
# exponent = 0x1e
# coefficient = 0x777777

target = 0x777777 * 2**(8*(0x1e - 0x03))
print(target)

target_hex = hex(target)[2:].zfill(64)
print(target_hex)

import hashlib

class Block():
    def __init__(self, data, prev_hash):
        self.index = 0
        self.nonce = 0
        self.prev_hash = prev_hash
        self.data = data

    def blockhash(self):
        blockheader = str(self.index) + str(self.prev_hash) + str(self.data) + str(self.nonce)
        block_hash = hashlib.sha256(blockheader.encode()).hexdigest()
        return block_hash

    def __str__(self):
        return "Block Hash: " + self.blockhash() + "\nPrevious Hash: " + self.prev_hash + "\nindex: " + str(self.index) + "\nData: " + str(self.data) + "\nNonce: " + str(self.nonce) + "\n--------------"

class Hashchain():
    def __init__(self):
        self.chain = ["0000000000000000000000000000000000000000000000000000000000000000"]

    def add(self, hash):
        self.chain.append(hash)

hashchain = Hashchain()
target = 0x777777 * 2**(8*(0x1e - 0x03))

for i in range(30):
    block = Block("Block " + str(i+1), hashchain.chain[-1])
    block.index = block.index + i + 1
    for n in range(4294967296):
        block.nonce = block.nonce + n
        if int(block.blockhash(), 16) < target:
            print(block)
            hashchain.add(block.blockhash())
            break