The Internet Draft for the message format to be used in S/MIME 3 is now
available; please see <http://www.imc.org/draft-housley-smime-cms>. This is
the replacement for PKCS #7 1.5, and is only slightly different. Strap on
your ASN.1 goggles and enjoy!
Two other parts of S/MIME 3 (the message spec and the optional security
enhancements) will be appearing shortly. The certs spec will appear in a
few weeks, once we finish with the v2 certs definition.
--Paul Hoffman, Director
--Internet Mail Consortium