John R Levine wrote: >> I have a lot more trouble understanding why t= needs to be kept than why >> x= needs to be kept. >> > > Without t= we have no idea when a message was signed, since there's no > particular reason that the Date: header has to contain the current date, > or even that there be one. > Sure; I haven't been clear on why we care when the message was signed, except as it affects the expiration of the signature (which x= expresses more directly). > >> As a signer, I would much rather specify an expiration time for the >> signature than to specify the time at which it was signed than to >> have the verifier add a fudge factor to the signing time and use >> that as the expiration. On this list, I have already heard numbers >> between 1 and 2 weeks for the fudge factor, so the signer would >> really have no idea how long the signatures are valid. >> > > But the signer is likely to have little idea of what the transit time > to the recipient will be. The basic justification for x= is that the > sender knows the transit time and the recipient doesn't. I've never > seen any justification for that, and it's easy to think of scenarios > where it's just wrong. > I don't see why the recipient would have any better idea than the sender on whether the transit time is acceptable.
I prefer x= over extrapolation of t= because it gives the verifier a simple, objective test to see whether the signature is "stale". -Jim _______________________________________________ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
