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bitcoinbook/code/proof-of-work-example.py
David A. Harding 2f0d7d8c3a Revert CC-BY-SA material added since the second edition
The commit ab5ae32bae is the last commit
for the second edition, so all changes since then are dropped except for
several commits for the third edition authored by Andreas Antonopoulos.

No attempt is made to remove CC-BY-SA or other licensed content present
in the already-published first or second editions.

This revert may itself be reverted for versions of the book published
under CC-BY-SA.
2023-02-01 06:31:10 -10:00

65 lines
1.8 KiB
Python
Executable File

#!/usr/bin/env python
# example of proof-of-work algorithm
import hashlib
import time
try:
long # Python 2
xrange
except NameError:
long = int # Python 3
xrange = range
max_nonce = 2 ** 32 # 4 billion
def proof_of_work(header, difficulty_bits):
# calculate the difficulty target
target = 2 ** (256 - difficulty_bits)
for nonce in xrange(max_nonce):
hash_result = hashlib.sha256(str(header) + str(nonce)).hexdigest()
# check if this is a valid result, below the target
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 = ''
# difficulty from 0 to 31 bits
for difficulty_bits in xrange(32):
difficulty = 2 ** difficulty_bits
print("Difficulty: %ld (%d bits)" % (difficulty, difficulty_bits))
print("Starting search...")
# checkpoint the current time
start_time = time.time()
# make a new block which includes the hash from the previous block
# we fake a block of transactions - just a string
new_block = 'test block with transactions' + hash_result
# find a valid nonce for the new block
(hash_result, nonce) = proof_of_work(new_block, difficulty_bits)
# checkpoint how long it took to find a result
end_time = time.time()
elapsed_time = end_time - start_time
print("Elapsed Time: %.4f seconds" % elapsed_time)
if elapsed_time > 0:
# estimate the hashes per second
hash_power = float(long(nonce) / elapsed_time)
print("Hashing Power: %ld hashes per second" % hash_power)