stega_lsb.py

import binascii
import sys

def byteFromBitstring(bitstring):
    return int(bitstring, 2)

def bitstringFromByte(byte):
    return ''.join([str((byte >> i) & 0x01) for i in range(7, -1, -1)])

def reveal(image, offset, localoffset):
    message = ''
    bitstring = ''
    pixel = offset
    while pixel < len(image):
        bit = bitstringFromByte(int(binascii.hexlify(image[pixel]),16))[-1]
        bitstring += bit
        if len(bitstring) > 7:
            message += chr(byteFromBitstring(bitstring))
            bitstring = ''
        pixel += localoffset
    return message

if __name__ == '__main__':
    if len(sys.argv) < 4:
        print "Dad LSB Tool"
        print "Usage: %s <file> <offset> <local offset>" % sys.argv[0]
        print "- offset      : from start of <file>"
        print "- local offset: between each LSB"
    else:
        print reveal(open(sys.argv[1], 'rb').read(), int(sys.argv[2], 16), int(sys.argv[3]))