Denis Pinkas wrote:
This is an answer to an E-mail from Francois Rousseau posted some time ago
about countersignatures.
As you will see the issue is more complex than it looks.
Indeed it is. There is also the issue of trust. A trusted countersigner
is a different beast from a trusted signer and likewise a trusted
countersigning CA is different from a normal end user CA.
I might trust an end user to sign a message (via a chain to a trusted
root) but I certainly wouldn't trust them to countersign a message
purporting to contain trusted timestamps and verifying chains in the
original SignerInfo.
This might be handled by some certificate extensions in the
countersigning certificate and the issuer certificate. This could either
be done either in a simple way (e.g. "certificate key approved for
countersigning" and "CA certificate can sign countersigning
certificates") or in a more intricate fashion ("trusted to countersign
with a trusted timestamp" etc etc).
Steve.
--
Dr Stephen N. Henson. UK based freelance Cryptographic Consultant.
For info see homepage at http://www.drh-consultancy.demon.co.uk/
Email: shenson(_at_)drh-consultancy(_dot_)demon(_dot_)co(_dot_)uk
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