As an addendum to the bibliography that Tim Cole posted, there are three good papers in the July 1993 edition of _Physical Review A_ (vol. 48 no. 1): "Information-theoretic limits to quantum cryptography" by Stephen M. Barnett and Simon J.D. Phoenix, "Quantum cryptography without conjugate coding" by Simon J.D. Phoenix, and "Quantum computers and intractable (NP-complete) computing problems" by Vladimir Cerny. - Mark - -- Mark Chen chen@netcom.com 415/329-6913 finger for PGP public key D4 99 54 2A 98 B1 48 0C CF 95 A5 B0 6E E0 1E 1D