Quote:
Originally posted by jaan
i think tankgirl just described one: all users are identified by their public key.
so whenever you communicate with a user in your hotlist, the software will issue a cryptographic challenge based on his/her public key. this way you can be 100% sure that the user you are chatting with really is the one you added to your hotlist in the first place (assuming that his/her private key hasn't leaked out).
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OK, well, that's all fine. I though were talking about user authentication. Identification is a pretty trivial issue by comparison. You can implement a P2P hotlist by performing a user search in the background. You can even ensure no one steals your identity by using public/private keys. However, this is VERY bandwidth intensive. I'm sure you've seen keys before, they're not exactly small. If everyone's running these searches on an ongoing basis, there will be some people with larger than expected bandwidth bills. (I think WinMX does not have a permanent hotlist because users are not identified uniquely enough, just by a small username.)
I mean authoritative authentication. As in, user A logs in, and everyone agrees that it is, indeed, user A, and he has access to so and so, not just because he says he's user A, but because everyone can authoritatively verify this. This problem is not a problem at all if you can have servers you trust do this for you. Who does this authentication on a free-for-all P2P network?