Russ Housley wrote:

Steve:
The reason for this requirement is that Ephemeral-Static Diffie-Hellman
(E-S D-H) is the mandatory to implement key management algorithm. The
output of E-S D-H is a KEK. So, the mandatory to implement key management
algorithm requires a way to wrap the CEK in the resulting pairwise KEK.
Russ
At 05:24 PM 3/31/99 +0000, Dr Stephen Henson wrote:

Is there a potential conflict with CMS 12.3.1? That is:
Any symmetric encryption algorithm that a CMS implementation includes
as a content-encryption algorithm must also be included as a key-
encryption algorithm.
As I understand this this means that a CMS implementation using IDEA
must also include a means to wrap content encryption keys with IDEA.
This would require additional information and a new OID
id-alg-CMSIDEAwrap for example.

My point is that the S/MIME IDEA draft spec specifies a way to use IDEA
as a content encryption algorithm but does not include details of how to
use IDEA as a key encryption algorithm.
My interpretation of the quoted paragraph from CMS 12.3.1 (which may
well be incorrect) in the context of the IDEA spec is that any
implementation using IDEA as a content encryption algorithm must also
support IDEA as a key encryption algorithm which the draft S/MIME IDEA
specification does not define.
Again my interpretation of this would be that IDEA cannot be used with a
conformant CMS application until an IDEA key encryption algorithm (and
associated object identifier) is defined as well.
Steve.
--
Dr Stephen N. Henson. http://www.drh-consultancy.demon.co.uk/
Personal Email: shenson(_at_)drh-consultancy(_dot_)demon(_dot_)co(_dot_)uk
Senior crypto engineer, Celo Communications: http://www.celocom.com/
Core developer of the OpenSSL project: http://www.openssl.org/
Business Email: drh(_at_)celocom(_dot_)com PGP key: via homepage.