match_hash.py

from Crypto.Hash import SHA256
import struct, random, yaml, time

# hash to match
h = SHA256.new(b"123456")
ref = int(h.hexdigest(),16)

# config
treshhold, timeout = 20, 120 # require AT LEAST 20 matching initial bits!

# run till keyboard interrupt and then save file
while True:
    matches, start_value, max_match, max_value = [], 0, 0, 0
    end_time = time.time() + timeout

    # generate a random start value
    for i in range(32):
        start_value = (start_value << 8) + random.randint(0, 2^8-1)

    try:
        value = start_value
        while time.time() < end_time:
            # update hash
            h = SHA256.new(str.encode("%d" % value))
            # extract infomation into int
            new = int(h.hexdigest(), 16)

            # compare bits
            v, i = format(ref ^ new, '0256b'), 0
            while i < 256 and int(v[i], 2) == 0:
                i += 1

            # write to file if enough similarity
            if i >= treshhold:
                matches.append([value, i])
                print("Match of %03d bits" % i)
                if max_match < i:
                    print("NEW MAX MATCH FOUND! %d" % i)
                    max_match = i
                    max_value = value

            # update value
            value += 1
    finally:
        print("Stopped at: %d" % value)
        with open("hash-file-%f.yml" % time.time(), 'w') as f:
            data = {"matches": matches, "start": start_value, "end": value}
            f.write(yaml.dump(data))
        print("Max (%d): %d" % (max_match, max_value))

Assignment for Information Security course: try to match as many first bits as possible to a certain reference SHA-256 hash value. This small script executes a simple brute-force matching by means of the PyCryptodome suite.