on 6/8/2003 12:47 PM Theodore Ts'o wrote: > In order for this to work, the request for the Hashcalc calculation > has to be done automatically. If it requires manual intervention > where the user sees the reject notice and then has to manually take > action --- of course, it's doomed to fail. So this is something which > would require modification to the MTA's in order for this to work. > > The easist way to automate such a scheme would be in the context of > your "replace SMTP" proposal; it's just a matter of using bare keys + > hashcash-style solution, instead of requiring a global PKI.
If a key was linked to a sender address, wouldn't that give somebody everything they'd need to send me mail (just send it as me, since I'm going to read my own mail even if nobody else does)? What's to prevent a group of blackhats in the ~Ukraine from having their farm of 3Ghz PCs generate error responses all day, just to gather keys to sell along with the associated addresses? How would I replace the key/address pair in all of the good repositories -- but not the bad ones -- after my key were compromised, especially if my own delivery server is responding to requests on my behalf? Isn't the only way out of this to require senders use certificates that can be validated, proving that the sender has access to a private key which roughly corresponds to that address? I'm in agreement that we don't need a "global PKI" to do any of this. We only (ha!) need a relatively simple and lightweight way to locate and retrieve public keys associated with specific resources (additional vouching systems would be useful but aren't immediately necessary). That particular problem isn't too tough to solve when limited to a scope that is somewhat smaller than "global PKI", and I think we'll actually get something like that relatively quickly. I also think this is mostly a chicken-and-egg problem at that level, and that we might find both the chicken and the egg at the same time if we're willing to look a bit. -- Eric A. Hall http://www.ehsco.com/ Internet Core Protocols http://www.oreilly.com/catalog/coreprot/