Steve:
CMS-12, Section 12.3.1 says:
For key agreement of RC2 key-encryption keys, 128 bits must be
generated as input to the key expansion process used to compute the
RC2 effective key [RC2].
X942-07, Section 2.1.3 says:
... For RC2-128, which
requires 128 bits of keying material, the algorithm is run once, with
a counter value of 1, and the left-most 128 bits are directly con-
verted to an RC2 key. Similarly, for RC2-40, which requires 40 bits
of keying material, the algorithm is run once, with a counter value
of 1, and the leftmost 40 bits are used as the key.
X942-07, Section 2.1.4 says:
RC2 effective key lengths are equal to RC2 real key lengths.
I think that we are consistent. CMS-12 is simply mandating that RC2 KEKs
be 128-bit keys, and X942-07 says that the effective key length cannot be
used to weaken the key.
Okay?
Russ
Return-Path: <owner-ietf-smime(_at_)imc(_dot_)org>
Date: Wed, 31 Mar 1999 21:24:42 +0000
From: Dr Stephen Henson <drh(_at_)celocom(_dot_)com>
Organization: Dr S N Henson
To: "ietf-smime(_at_)imc(_dot_)org" <ietf-smime(_at_)imc(_dot_)org>
Subject: RC2 keylength in CMS.
In CMS there are still a couple of references to the RC2 key length
being always 128 bits. Specifically 12.3.1 and 12.6.
Whereas X9.42 refelects the change and that RC2 effective and real key
lengths are equal.
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/
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