Dave writes:
Disregarding the "quantum properties of light" issue, if Eve can listen in on every communication between Alice and Bob about their keys, then doesn't she have enough information to reconstruct the key herself?
By "disregarding the quantum properties", I assume you are asking about deterministic cryptosystems. Eve does not have sufficient information if Alice and Bob use, say, Diffie-Hellman key exchange (DH). As I said, that's why DH is so clever. :) (cf. any good crypto text) But that's patented (for now), and we were asked about a patent-free solution. -Futplex <futplex@pseudonym.com> "We live in a time when...individual rights are constantly expanded" -Sen. Orrin Hatch (R-UT), speaking in support of an anti-flag-desecration Constitutional amendment