On Fri, 6 Dec 2002, at 13:41 [=GMT-0800], Fred Baker wrote: > I think it was Steve Bellovin that suggested a procedure for reducing the > utility of spoofing source addresses in emails; if not, it was me and I > happened to suggest something his favorite algorithm fit into, by having a > host in each mail domain (mailid.example.com) be able to assert that its > domain had or had not sent an email within a given recent time period > whose MD5 hash, when divided by <vector of prime numbers> resulted in > <vector of remainders>. I could write that up in an internet draft if folks > think it makes sense. That would be a more global procedure that didn't > require a PKI and only addressed spoofed addresses. Spammers would be the first to set up your mailid host. They will have had years of experience to find holes in the system before you've convinced everyone to adopt or accept the mailid. It might be easier to write a new protocol to succeed email, instant messaging, mobile phones (something useful in itself) with built-in abuse control from the start.