That's pretty much what I was talking about when I said that it may be possible to clone an arbitrarily large proportion of photons - and that Quantum Cryptography may not actually be secure.

A key point is the probability that the measurement/cloning operation has of disturbing the original state. Errors at the receiver are assumed to be the result of eavesdropping. The current canoncial paper on how to calculate the number of bits that must be hashed away due to detected eavesdropping and the inferred amount of undetected eavesdropping is "Defense frontier analysis of quantum cryptographic systems" by Slutsky et al: http://topaz.ucsd.edu/papers/defense.pdf (I don't want to take a position on whether cloning is or isn't possible - that's way out of my area of expertise!) --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]