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Re: Comparing email header fields with certificate contents...?

1997-07-07 09:33:29
From: John Gardiner Myers <jgmyers(_at_)netscape(_dot_)com>

(If email address is the most stable thing in your life,
more stable than your employer, your residence address, or your ISP,
then you as an individual could choose to make it your Certified
primary identity for personal communications.

Historically my published email address has been more stable than any of
my employer, residence address, or ISP.

Huh?  For how long have you been jgmyers(_at_)netscape(_dot_)com?  As of Dec '96
(sasl draft -07) you were jgm+(_at_)cmu(_dot_)edu(_dot_)  And if you still get 
mail sent
to the old address, is it based on the kindness of cmu maintaining an
account for you with a .forward file, or on a commercial email
forwarding service?  How, except for intuition, am I expected to know
that the person with a Netscape address is the same person that wrote
SASL?  Even if you had certificates for both the old and new email
addresses, how would they be linked together for identity purposes?

If the CA is only certifying a (one-time) association
between a key and an email address, that is a pretty weak assertion.
Certainly not something I'd pay money for :-).

I'd certainly be unwilling to pay for any messaging cert that doesn't at
least give me this assertion.  I could care less about wheter you're
"David P. Kemp" at a certain residence or "David P. Kemp, Jr." at the
same or other residence, I care whether or not a message is from or to
the same thing as was the last time I interacted with whatever
"dpkemp(_at_)missi(_dot_)ncsc(_dot_)mil" is.

What you should care about is that I wish to be known as "David P.
Kemp" in some unambiguous naming domain of my choice, regardless of
whether I send/get email from/to dpkemp(_at_)missi(_dot_)ncsc(_dot_)mil or 
or 138954,2347(_at_)compuserve(_dot_)com or 

Even "Elizabeth Taylor" is really "C=US, O=SAG, CN=Elizabeth Taylor" since
it is the business of the SAG to establish name permanency and prevent
name reuse regardless of marriage, employer, address, etc.  If a middle
name is required as a disambiguator, they require it.  If a full common
name has already been taken, the poor actor who comes along second has
to pick a different one.  Other naming authorities/domains may have
different rules :-).

If you want to use the DNS part of an RFC822 address as the naming
authority for your permanent identity, that is fine.  You can choose
to get certs with an RFC822 address as your name.  But that is a
totally separate function from the business of routing messages to a
location where your UA can find them.  Forcing the two to be linked
together in a certificate is a gross layering violation.  If S/MIME
forces the UA to use the email address in a cert, how could I send
an S/MIME message to my wife from the IETF terminal room?

There is no security benefit to requiring delivery addresses in
certificates, since if the message gets misdelivered it can't be read
anyway.  The worst that can happen if the user misconfigures the UA
is that the message won't get to it's intended recipient.  Requiring
the CA to certify message routing information will just gum up the
works when the routing is not static.


* You can already use an rfc822Name as your certificate identity 
  (subjectAltName) if you wish to do so.

* But requiring CAs to certify email delivery addresses for *all*
  S/MIME users is unworkable if *any* users change addresses,
  and certification provides *no* identity-linking benefit if the
  email delivery infrastructure does not enforce name uniqueness.