Stephen:
I understand that S/MIME v1 can't support DSA keys because it requires
the messageDigest, which DSA does not provide. And if authenticated
attributes are present, the messageDigest attribute (among others) MUST
be present.
This is not correct. If you look at the signed-data syntax in PKCS#7
version 1.5, you can see that encryptedDigest can easily carry a DSA
signature value. The syntax works fine, although the english desciption of
the process is RSA specific. I do not think that any implementation would
be confused is the appropriate OIDs are used.
DSA is not one of the algorithms supported by any S/MIME v2 implementation
that I know about. I am sure that someone on the list will correct me if I
am unaware of one.
Would some kind soul please tell me if S/MIME v2 gets away from this
somehow and therefore allows DSA keys, or do we have to wait for S/MIME
v3?
The CMS specification fixes the wording so that any signature algorithm can
be used. The syntax does not change.
I can't really tell much difference between S/MIME v1 and v2 in terms of
ASN.1 except for the application/mime types. Do I have this right
[broad strokes]:
v1 - RSA developed this
v2 - continuation of v1, only under IETF
v3 - DSA, signed receipts, security clearance, MLA's
No. S/MIME v2 was developed by RSA. It is in the process of being
documented in Informational RFCs. S/MIME v3 is being developed in the
IETF. S/MIME v3 is building on S/MIME v2, and it adds additional features
(including key management algorithm independence, signed receipts, security
labels, and support for mail lists).
Mainly what I'm jonesin' for is DSA; the other stuff can wait for my
purposes, for the moment.
Enjoy,
Russ