shanty.py

import sha
import sys

f = open("/dev/urandom", "rb")
while 1:
    sys.stderr.write(".")
    message0 = f.read(256)
    cs0 = sha.new(message0).digest()[:2]

    flip_bit = 1 << (ord(f.read(1)) % 8)
    flip_byte = ord(f.read(1))
    message1 = message0[:flip_byte] + chr(ord(message0[flip_byte]) ^ flip_bit) + message0[flip_byte+1:]
    cs1 = sha.new(message1).digest()[:2]
    if cs0 == cs1:
        print cs0.encode("hex"), flip_bit, flip_byte                                                                           
        print message0.encode("hex")
        print message1.encode("hex")
        break