Fun with one time pads!

cypher.py

#!/usr/bin/env python
import Image
import os, sys
if __name__ == "__main__":
	if len(sys.argv) != 4:
		print("Usage: %s secret pad output"%(sys.argv[0],))
		sys.exit(0);
	secret = Image.open(sys.argv[1])
	secret.convert("RGB");
	secretPixels = secret.load();
	pad = Image.open(sys.argv[2])
	pad.convert("RGB");
	padPixels = pad.load();
	if secret.size != pad.size:
		print("Both images need to be the same size!");
		sys.exit(0)

	w, h = secret.size

	output = Image.new("RGB", (w,h))
	pixels = output.load()
	for x in range(w):
		for y in range(h):
			s = list(secretPixels[x,y])
			p = list(padPixels[x,y])
			#if len(p) != 4:
			#	p+=[0]
			#if len(s) != 4:
			#	s+=[255]
			try:
				pixels[x,y] = tuple([s[i] ^ p[i] for i in range(min(len(s),len(p)))]) #(s[0]^p[0],s[1]^p[1],s[2]^p[2],s[3]^p[3])
			except IndexError:
				print("%d %d"%(len(s), len(p)));
				raise
	output.save(sys.argv[3])

generateOTP.py

#!/usr/bin/env python

import Image
import os, sys

if __name__ == "__main__":
	if len(sys.argv) != 4:
		print("Usage: %s width height output"%(sys.argv[0],))
		sys.exit(0)
	width = int(sys.argv[1])
	height = int(sys.argv[2])
	outfile = sys.argv[3]
	img = Image.new("RGBA", (width,height))
	pixels = img.load();
	w, h = img.size
	for x in range(w):
		for y in range(h):
			pad = os.urandom(4);
			pixels[x,y] = (ord(pad[0]), ord(pad[1]), ord(pad[2]), 255)#ord(pad[3]));
	img.save(outfile);
	#print(os.urandom(4).encode("hex"));