Blockchainの魚と熊掌シリーズ(20)のpow簡単なテスト

#!/usr/bin/env python
# example of proof of work algorithm

import hashlib
import time

max_nonce = 2 ** 32 # 4 billion

def proof_of_work(header, difficulty_bits):

    target = 2 ** (256-difficulty_bits)
    for nonce in xrange(max_nonce):
        hash_result = hashlib.sha256(str(header)+str(nonce)).hexdigest()

        if long(hash_result, 16) < target:
            print "Success with nonce %d" % nonce
            print "Hash is %s" % hash_result
            return (hash_result, nonce)

    print "Failed after %d (max_nonce) tries" % nonce
    return nonce

if __name__ == '__main__':

    nonce = 0
    hash_result = ''

    for difficulty_bits in xrange(32):

        difficulty = 2 ** difficulty_bits

        print ""
        print "Difficulty: %ld (%d bits)" % (difficulty, difficulty_bits)

        print "Starting search..."

        start_time = time.time()

        new_block = 'test block with transactions' + hash_result

        (hash_result, nonce) = proof_of_work(new_block, difficulty_bits)

        end_time = time.time()

        elapsed_time = end_time - start_time

        print "Elapsed time: %.4f seconds" % elapsed_time

        if elapsed_time > 0: 

            hash_power = float(long(nonce)/elapsed_time)
            print "Hashing power: %ld hashes per second" % hash_power

python pow.py