Oh .. actually I just thought about it .. I suppose that XORing with a pseudorandom sequence would probably just add a lot of noise but still allow the voice to be heard if it was loud enough ... I guess a better way would be to group the samples into windows and shuffle the samples within each window by the pseudorandom function. Unfortunately the window size would have to be substantial (enough for 1/100 second or so) to garble the lower frequencies in human voice .. this would use a large amount of registers in even the largest PICs. I suspect that smaller windows would suffice since most of the frequencies that allow us to distinguish syllables from one another are towards the higher end of the spectrum. In any case, I would be interested in hearing your results if you pursue a scrambling algorithm like this. Sounds fun! Good luck, Ken