Compatibility between S/MIME v2 & v3 signatures

[Gwangsoo Rhee <[e-mail]>]

Hello, everybody.

Many documents including draft-ietf-smime-rfc2630bis-08.txt
claim that S/MIME v2 & v3 signatures are compatible, BUT:

Sec. 9.4 of RFC 2315 (PKCS #7 v1.5) states about the signature
generation:

   The result of the
   digest-encryption process is the encryption with the signer's private

   key of the BER encoding of a value of type DigestInfo:

   DigestInfo ::= SEQUENCE {
     digestAlgorithm DigestAlgorithmIdentifier,
     digest Digest }

And sec. 5.5 of RFC 2630 (CMS) states:

   The input to the signature generation process includes the result of
   the message digest calculation process and the signer's private key.

This RFC has no mention of DigestInfo structure.
It seems to me that DigestAlgorithmIdentifier doesn't
contribute to the signature generation, and in that case
those two signatures cannot be compatible.

Can anyone please point out where I got this wrong?

Thanks.

--

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Gwangsoo Rhee <[e-mail]>
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