I invented a very trivial sample obfuscation algorithm for low CPU usage (I was probably not the first to come up with that):
- Create a noise file that you ship with the samples. This is your public key
- Mix that noise with your sample with an offset (individual for each sample, makes it a bit harder)
- when playing back sum the negative noise with the correct offset. Summing is cheap.
Caveat: make sure that your wave file accepts values over 1.0f (since you cannot rule that out).