While the pseudo-random bit sequence algorithm used in the Computer Shopper article is weak, it is important to note that the article is on the right track. However, a one time pad based on PRBS is only as secure as the PRBS itself. If the author did not state this, he was remiss. There *are* cryptographically strong pseudo-random bit generators. A one time pad based on a CSPRBS would be as secure as the underlying 'hard' problem. For example, Blum and Micali's paper "How to Generate Cryptographically Strong Sequences of Pseudo-Random Bits" (Nov. 84 SIAM), details a scheme based on the discrete log problem. Essentially, this system is based on selecting bits from successive exponentiations of a seed. If you could guess the next bit to be selected, without knowing the seed, you could reverse this into an algorithm to solve the discrete log problem. The Blum and Micali paper also references a paper by Shamir (which I have not read) called "On the generation of cryptographically strong pseudo-random sequences" 8th International Colloquium on Automata, Languages and Programming, Lecture Notes in Coputer Science, 62, Spring-Verlag, New York, 1981. The difference being that the Shamir scheme generates *numbers* while the Blum/Micali scheme generates *bits*. I try never to label anyone a moron until I am sure their stupidity is not just my failure to communicate. Scott Collins | "Few people realize what tremendous power | there is in one of these things." | -- Willy Wonka ...................................................................... Apple Computer, Inc. | phone: 408 862-0540(v), 974-6094(f) 1 Infinite Loop, MS 301-2C | AppleLink: SCOTTCOLLINS Cupertino, CA 95014 | internet: collins@newton.apple.com