pow.py

#!/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