Re: draft-ietf-impp-cpim-03.txt (faster crypto)

I'm resending this message because I haven't seen it show up on
the list.  Apologies if it has and I missed it.

draft-ietf-impp-cpim-03.txt states:
 
    A version of these specifications, which permitted re-use
    of the public key across multiple messages, would greatly reduce
    instant messaging overhead.
 
First, I'm guessing this was supposed to read "symmetric key"
instead of "public key".

Second, at least in the case of S/MIME, there's an easy way to
re-use the content encryption key that doesn't require any changes
to the S/MIME specification.  This comes from SET, but the idea is
that peers can re-use the same symmetric encryption for a series
of messages, and the sender merely generates the encrypted
symmetric key blob once, populating each PKCS#7 with that same
blob.  The recipient, if they've implemented this optimization,
can use a cached symmetric encryption key if they notice the
same encrypted key blob in the PKCS#7.

-brian
[email protected]




  [reminder: [email protected] for non-technical discussions, please]