Denis Pinkas wrote:
I do have a strong preference. :-)
In the pkix WG we are discussing the OCSP protocol, where basically
giving the reference of a certificate it should be possible to know
*on-line* from an OCSP whether this certificate is or is not revoked.
If this is done in the context of S/MIME then we would extract that
reference and then send it to the OCSP. Ideally a COPY and PASTE
operation would be nice: the same data structure should be used for both
the SMIME WG and the PKIX WG.
The proposal of using simply the hash of the certificate does not work
... because of the minimum assumption we are making in the PKIX WG: the
OCSP has only access to the newest CRL but no access to the individual
certificates themselves. Under such assumption the OCSP is thus UNABLE
to verify the hash of the certificate and therefore to make sure it is
pointing to the right certificate. For solving the case Ambarish
proposed to replace the hash of the certificate by the hash of the
public key of the CA, which is a technically adequate solution.
I may be missing something here but why can't the standard "outer"
issuerAndSerialNumber be used? Under the proposal (at least how I meant
it) it would still be there.
The extra binding caused by the SigningCertificate attribute crucially
relies on the fact that the authenticated attributes are signed. If the
signature on the authenticated attributes cannot be checked (e.g. if the
senders certificate is not available) then checking the
IssuerAndSerialNumber of the SigningCertificate (assuming it is present)
is no better than checking the outer unsigned issuerAndSerialNumber.
If there is a situation where an agent would have access to enough
information to verify the signature on the authenticated attributes
(which would as a bare minimum require the senders public key) but not
have access to the senders certificate then yes I agree this would be a
problem.
Steve.
--
Dr Stephen N. Henson.
UK based freelance Cryptographic Consultant. For info see homepage.
Homepage: http://www.drh-consultancy.demon.co.uk/
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