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To: spock(_at_)RSA(_dot_)COM, ietf-smime(_at_)imc(_dot_)org,
Date: Tue Apr 15 22:44:56 1997
In the world of peer-to-peer store-and-forward communications (e.g.
email) there really is no negotiation possible at "start of
communications". This is especially evident in the case of a multicast
message, i.e. sending a message to a bunch of recipients.
In such an environment, negotiation can be done either out of band
beforehand (e.g. by looking up some entries in a directory) or via
exchange of email by the end users who are not always savvy enough to
effectively negotiate encryption algorithms and key sizes. It was our
intent when creating S/MIME to provide some base level of
interoperability possible among all S/MIME-enabled user agents (i.e.
the "MUSTS") and an easy path to negotiating the use of the strongest
possible encryption where both ends are capable (i.e. the "SHOULDS").
Since certificates are in any case a prerequisit, supported/prefered
algorithms could be published as extended properties of an X509.
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