I don't know much about his "optical noise" encryption, but Scientific American ran an article in the Amatuer Scientist column outlining an encryption scheme involved much the same ideas. Their scheme was to find, and digitize a chaotic source as a carrier signal and then add the information to the signal. Decryption involved subracting the source signal from the encoded one. Information encrypted this way would be positively unbreakable by anyone without the chaotic source, as the whole scheme is entirely random. The biggest problem is of course, transmitting the source in a secure manner. It is not enough to know the configuration of the generator of the source, unless you also the _exact_ initial conditions (which are, of course, impossible). One solution to this problem might be to use a recursive equation to generate a source from a small (one-hundred+ digit) seed, and the number of iterations necessary to reproduce the source. The nice thing about this is that the equation could also be customized, something like: x= (k)(x^2)+a, where "a" and "k" are constants that may be altered, thus providing two methods of encryption. This scheme would also be a solution to the problem of the source being corrupted during transmission (which would ruin any attempts to use it). But the equation and the seed would still have to be transmitted somehow. Hmmm.... you could openly send the seed and the encoded information, and then call the reciever to tell them to convert a given sentence into decimal equivalent...etc