Contempt of court

I wouldn't want to encourage anyone to contempt of court, but, strictly hypothetically, there is a very simple way to answer the request to hand over keys to encrypted data. Simply assure that you have a copy of the encrypted data available, then construct one-time-pad data of the same length as the encrypted data, such that when the two are XORed, you get your choice of plaintext. Hand over the "one time pad." This argues powerfully that one might want such one time pads available and in use even if you are really using a more convenient encryption technology. Kids: don't do this at home.