May 20, 2003
Email whitelists, p2p and webs of trust
I commented on Julian's site.
Doubtless you know this already, but the problem lies in just how well you 'trust' the other resources. It would be rather easy for a system with a membership to accept inquiries from it's members about other members.
As in, if you belong to group A then you could ask it whether user X also belonged to the group. One safe way to do this would be with SHA1 hashes. You don't ask if the address is known, you only ask if the hash is known. That way you're not feeding the group server with fresh addresses. You're passing it a hash that it can't decode. It can only see if it already knows of an address with that hash.
The downside, of course, is that someone that knows the hashes (and they're not likely to be randomly guessed) would be able to 'tell' if a given user 'belonged' to it. This would allow the opportunity for such services to act as intermediaries between different services. I could ask service A if it knows about user X. Service A would, in turn inquire (unbeknowst to me) of service B. I'd only be getting an answer back from service A. This presumes that I'd trust service A to make such proxies for me. Service A could likewise proxy such requests anonymously. As in, service B only sees the request coming from service A, not from me directly. The assumption there is that the services would likewise trust each other for such things.
What's needed is a web of trust. One that allows checks and balances to be applied, but only as needed. As it stands now there's very little available in regard to decent user interfaces for managing this sort of thing. Much like PKI, I'd want a system like this to be able to invalidate or otherwise require renewals of such look ups. At some point it may come to pass that service A is compromised (marketing droids have taken over) and should no longer be trusted. I'd want this to be something my other services would be capable to providing to me.
Trouble is, how to make this a process that doesn't torment the users?
