Regarding the suitability of embedding email addresses in certificates,
would it be fair to say that domains willing to live with permanent email
identities and narrowly defined delivery patterns could have a standardized
means of describing equivalent email addresses?
Hard to say. The PKIX crowd put in case folded addreses without, as
far as I know, asking anyone in the SMTP community whether that's a
good idea. While nobody thinks it's likely that Fred@example,
FRED@example, and fred@example would correspond to different people,
once you get past case folding you quickly run out of popular
techniques, and even case folding is hard in EAI since the folding
rules are specific to each language.
It's hard to say because the entire idea of defining a general
"canonicalization" operation for email address as a solution for various
problems is, as I have previously pointed out, nonsensical.
There are problems, such as the address equivalence tests mailing list managers
are obliged to perform, where a single canonicalization operation is both
necessary and sufficient. And there are problems, such as looking up
the certificate/private key to use for an address, where anything based on
canicalization will at best be a partial solution only applicable to
administrative domains that meet some very specific criteria, and a better
solution won't use canonicalization at all.
More generally, this entire discussion has taken on the characteristics of an
antipattern we see regularly in customer support: The customer has a
problem, settles on a particular solution and then asks us how to implement it.
Sounds fine, right? Except the solution they've settled on is either
unworkable, impractical, unimplementable, fails to solve the problem, or
some combination of the four.
And then we invariably spend a bunch of time wandering around before we're
able to back things up to the actual problem. Which at least we might have
a chance of solving.
And it's the same here. Painful though it may be, it's becoming increasingly
clear that we need to back up to the original set of problems that started
this discussion.
I originally thought that backing up to the problem of how to determine various
properties of an address was sufficient. But although I believe all of the
motivating problems here do reduce to property lookup, I now see that we're
going to have to go back further than that.
Ned
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