I think Shepardofchaos way was the best, im using something similar to it. But when it comes to saving the picture i would use savepicture, then after that u need to compress the file, by either zipping it or executing a converter to make jpg's or gifs. To encrypt, try search for it here, i have seen some good ways of encrypting here. I liked that one that xors the byte array against a result of a random seed.