Jeff,
Just to make sure I understand what train you're on, the change your
proposing should apply equally to PEM/MIME and RFC 1421, correct? If
this is not true, then your proposal contradicts one of our design
goals, which is to support the same functionality available in RFC 1421.
Either answer is okay, I just want to know the scope of your proposal,
since we need to know before we can call for a consensus from the
working group on whether they would like to drop the identifiers.
You propose:
Of all the identifier forms outlined in the PEM/MIME draft for use in
Originator-ID and Recipient-ID fields, we believe that the public key
identifier alone is sufficient:
You certainly present a good argument in favor of having only the public
key identifier. RFC 1421 specified two identifiers: issuer name/serial
number pairs or certificates. Based on community feedback we proposed
to augment the PEM specifications to allow 3 additional identifiers:
distinguished name/selector
email address/selector
arbitrary string selector
Conceptually, we view the public key identifier as the same as the
certificate identifier in 1421 and the issuer name/selector (serial
number) identifier is the same in both. Each of these identifiers
provides information that can be used to locate the required public key.
From an implementation point of view, it is possible to view these
identifiers as "handles" that indicate the required public key, i.e., as
an implementor you need not parse the individual values but rather you
can use the pair as single unit. Thus, conceptually, you need only
support two identifiers: the key itself and a "handle" for it.
There are several reasons why identifiers are useful.
o Public key's are large. Some folks will not want to distribute them.
Let me observe that the PGP community is in touch with this issue
since they typically only distribute key footprints.
o There is community of users who would prefer not to publish their
public keys. Rather, they will prefer to use psuedonyms that are only
useful to the recipients.
o If you remove textual information from the identifiers, users will not
be able to get any useful information out of message. In particular,
if a message fails to verify there will be no help for the user.
(Well, perhaps that's a bit strongly stated. One could argue that the
message content itself may be helpful as well as the envelope of the
message.)
Jim