Hi, I realise this is slightly OT for the list, but there'll be a lot of people on this list with experience in cryptography, so here's as good a place as any to ask this ;). Does anyone know of a cipher that meets the following two requirements: - You cannot determine the key from the encrypted & decrypted text (by key I mean the 'session' key) - You can decrypt in a 'nested' fashion - eg, if E(M,x) means encrypting M with key x and D(M,x) means decrypt M with key x, then the algorithm should satisfy D(E(E(M,a),b),a) == E(M,b)
What I'm thinking (and I'm sure I've come across this before) is that you could exchange secret keys with someone sans public-key crypto by doing the following (Where M is the private key/message to be exchanged): Alice sends E(M, a) to Bob Bob sends E(E(M, a), b) back to Alice Alice decrypts the result: D(E(E(M, a), b), a) to get E(M, b) and sends this to Bob Bob decrypts E(M, b) to get M. Anyone know of a cipher that could do that, or if it's possible at all? Sorry for the OTness, Nick Johnson _______________________________________________ freenet-tech mailing list [EMAIL PROTECTED] http://lists.freenetproject.org/mailman/listinfo/tech
