From: Bill Frantz <frantz@netcom.com>
Date: Thu, 25 Jun 1998 23:32:36 -0700 (PDT)
To: cypherpunks@toad.com
Subject: Re: Skipjack extensibility
In-Reply-To: <199806250705.JAA31711@basement.replay.com>
Message-ID: <v0311077bb1b8f7dc3b54@[207.94.249.99]>
MIME-Version: 1.0
Content-Type: text/plain


At 11:05 PM -0800 6/24/98, Anonymous wrote:
>NSA made a claim that Skipjack couldn't be extended past 80 bits of key. Most
>plausible explanation to my mind is that they're lying. Second is that
>there is
>an attack against a class of Skipjack-like ciphers that requires only a few
>plaintexts and 2^80 operations. Third is that some common key-lengthening
>tricks like those for 2-key-3DES, DES-X, and DEAL fail when applied to
>Skipjack. I can hardly fathom one resistant to all three, but I guess it's
>possible with NSA.

3DES is useful because DES does not form a group.  To the best of my
knowledge, Skipjack has not been analysed in this area (outside of Never
Say Anything).


-------------------------------------------------------------------------
Bill Frantz       | If hate must be my prison  | Periwinkle -- Consulting
(408)356-8506     | lock, then love must be    | 16345 Englewood Ave.
frantz@netcom.com | the key.     - Phil Ochs   | Los Gatos, CA 95032, USA