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Re: Question: DSA and S/MIME v2? v3?

1998-01-27 17:39:37
Chris:

No.  Use of DSA does not determine wheteher or not authenticated attributes
are used.  DSA may be used with authenticated attributes, and DSA may be
used without authenticated attributes.

As far as I know, DSA is always used with SHA-1.  The DSA requires a
160-bit message digest input.  SHA-1 is the only message digest that I know
of that generates a 160-bit value.

Russ


At 02:04 PM 1/23/98 -0500, Bonatti, Chris wrote:
Russ,

   Is the converse of this statement true?  If using DSA, does that
essentially mean that authenticated attributes cannot be used?

   I would assume that you could specify DSA as the signature algorithm, and
specify an arbitrary hash algorithm to address the messageDigest attribute.

Chris


___________________

Russ Housley wrote:

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.






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