Subject: RE: key usage - key encipherment or data encipherment

From: "Hallam-Baker, Phillip" <[email-masked]>
Date: Thu, 19 May 2005 11:33:04 -0700

I have been following the thread, I think the cures proposed may be
worse than the problem.

I think that the sentences can be adequately clarified by stating that
dataEncipherment is to be set if the key is to be used to directly
encipher data, i.e. without the use of an intermediate session key.

I accept that this is not a particularly interesting use of
dataEncipherment, the only protocols I can think of in which data is
directly enciphered with a public key is Chaumian cash schemes and
similar where blinding is used. Everywhere else you want to use a
packaging scheme because the strength of bit 0 in RSA is pretty good but
the strength of bit 1024 with a 1024 bit key is pretty bad.

---

From: Eric Norman <[email-masked]>
Date: Thu, 19 May 2005 16:16:28 -0500

> encipher data, i.e. without the use of an intermediate session key.

I might as well chime in with my take, which is different yet.  And 
since
those two bits have already appeared in standards documents, probably
not worth anything.

I think that from a user's point of view, all the user cares about is 
that
the data is protected in transit and perhaps at rest.  The user doesn't
really care or even want to know whether an intermediate symmetric key
in involved or not.  From that point of view, the distinction seems 
rather silly.

Now, if someone came up with a key escrow scheme that would escrow
the symmetric key, then that might be interesting.  But that's yet 
another
thread.

Eric Norman
University of WIsconsin