Don't think I will bore the list with it, But a slightly more complex version of this scheme was one of the major tactical medium security voice scrambling systems used by the US in the 70's and 80's and even to a slight extent into the 90's on military radio circuits. The military version is called Parkhill and the crypto gear is the KY-65 and KY-75. At one time (in the 70's) it was used for at least secret traffic. It was downgraded a couple of times since and is now considered obselete and compromised. A Parkhill crypto box can be seen in the NSA museum... The NSA version used time inversion (playing voice samples backwards) and faster shuffling than this one does, and possibly a more secure key generator. But it is rumored to have been broken by more than one opponent, perhaps including drug cartels. Its appeal and why it was so extensively used for a while is that it interfaces to normal voice radio gear at the audio input and output level rather than requiring different modulations and complex digital modems integrated into the radio. It also gives pretty good speech quality and speaker recognition. Its primary replacement is the ANDVT digital voice terminal which takes advantage of modern DSP technology to implement modems usable over radio links and vocoders which can produce acceptable speech at 1200 or 2400 baud. Dave Emery die@die.com