Mining the nonce for a take home exam at NYU Stern

blockchain.py

import hashlib
import time
import re
from datetime import date

# Block information
block = 1
data = 'German gets a PD'
prevHash = '0000000000000000000000000000000000000000000000000000000000000000'

# Number of leading zeros
difficulty = 10
targetHash = ''.zfill(difficulty)


def leading_zeros(s):
    return len(re.match('^0*', s).group())


start = time.time()

print('EMBA A21 - Digital Currency - German Attanasio')
print('Start time: {}'.format(date.today()))
print('Block: {}, Data: {}, difficulty: {}, prevHash: {}'.format(
      block, data, difficulty, prevHash))

nonce = 0
bestNonce = nonce
bestDifficulty = 0
foundNonce = False
while not foundNonce:
    blockStr = "{}{}{}{}".format(block, nonce, data, prevHash)
    hash = hashlib.sha256(blockStr.encode()).hexdigest()
    currDiff = leading_zeros(hash)

    if currDiff > bestDifficulty or currDiff == difficulty:
        end = time.time()
        print('Leading zeros: {}, time: {:.2f} sec, nonce: {}, hash: {}'.format(
              currDiff,  end - start, nonce, hash))
        bestDifficulty = currDiff
        bestNonce = nonce

        if currDiff == difficulty:
            foundNonce = True
    nonce += 1