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Is there a way to take published public keys and combine them with your own in such a way that your identity is not compromised, but it is clear beyond a doubt that you control one of a set of public keys?
An obvious solution would be a shared public key/private key pair between a number of users then use them for digital signatures and route the messages through an anonymous server. You could also have an arbitrated blind signature protocol whereby trent shares a keypair with all users. bob encrypts his comment, M with the key he shares with trent. On recieving it trent carries out a blind signature on it and publishes it, as trent knows only bob has the shared key, K he knows bob said M but as it is a blind sigature and he is likely to be signing a lot of messages (trent is of course a computer program) he doesn`t know which message came from bob. Also Chaums group signatures could be used but unfortunately the arbitrator can find out who said what, but does not normally know. Also trent can forge digital signatures with this protocol. Chaum further mentions protocols for this sort of thing that do not even need an arbitrator but I don`t have the papers on this. -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia Charset: cp850 iQCVAwUBMoyPCr5OPIRbv66xAQE6pQQAvs/NVY8s6Uid186CAQf8Q+iZucYtzRM7 iNjR0RkiNMnYACgHG0NO9UfkPgKGdomMQrGJFubH9O2/fnbMAIGZh8gv+k9P7iYl 5lMfCtCQe4AgeCyS2YRLMEYQiI6MAqWn4HoTzA58gWRbtOHeIZNpw/vc/hTqBbA7 3sDsOGYqqCk= =kiS8 -----END PGP SIGNATURE----- Datacomms Technologies web authoring and data security Paul Bradley, Paul@fatmans.demon.co.uk Paul@crypto.uk.eu.org, Paul@cryptography.uk.eu.org Http://www.cryptography.home.ml.org/ Email for PGP public key, ID: 5BBFAEB1 "Don`t forget to mount a scratch monkey"