On Wed, 08 Jan 2003 09:26:04 -1000, Jason Coombs said: > Aloha, > > The public key is derived from the private key. Anyone in possession of the > private key is by definition also in possession of the public key. The same > is not true in reverse, a party can possess the public key without the > ability to (reasonably) discover the matching private key. Actually, it's quite possible for the same private key to match with two or more different public keys. So for instance, you could have: public, private = 37, 13 public, private = 53, 13 These are of course 2 different key *PAIRS*. What you may be misunderstanding is that the key *pair* is derived from one number, which is usually the product of two primes. I'd have to do a quick UTSL, but I believe that in addition to the "private" key, PGP also stores enough other info (like the modulus used, etc) to allow regenerating the public key, and anybody who compromises the system gets *all* the different data items saved. But strictly speaking, having the private key *only* doesn't get you the public key... Schneier's "Applied Cryptography" has a good chapter on RSA that explains how this all works... -- Valdis Kletnieks Computer Systems Senior Engineer Virginia Tech
This archive was generated by hypermail 2b30 : Wed Jan 08 2003 - 17:54:00 PST