Phil Smiley writes:
Basically, including yet another algorithm identifier provides yet
another opportunity for two users to fail to interoperate. Although
it's probably true that we'll just recommend exactly one (e.g., MD5),
there's always the possibility that it will need to be changed.
If the digest algorithm used is the same as is used for digital signatures,
is the opportunity for non-interoperability really increased by digesting
the public key also?
Hiding the public key will probably be of more interest to people who
are making encrypted, not signed, messages. And for an encrypted
message, there is no digest algorithm to re-use in this way.
- Jeff