From: Dave Emery <die@die.com>
Date: Sun, 11 Oct 1998 10:10:00 +0800
To: Anonymous <nobody@replay.com>
Subject: Re: DESX
In-Reply-To: <199810102206.AAA06060@replay.com>
Message-ID: <19981010215151.A628@die.com>
MIME-Version: 1.0
Content-Type: text/plain



On Sun, Oct 11, 1998 at 12:06:14AM +0200, Anonymous wrote:
> | So what's DESX?
> 
> DESX is a modification of DES which uses a 64+56+64 bit key, with
> what is called "pre- and post-whitening".  Specifically, break the key
> into three pieces, 64 bit K1, 56 bit K2, 64 bit K3.  Then DESX is
> defined by:
> 
> 	C = K1 xor DES (K2, K3 xor P)
> 
> where P is plaintext, C is ciphertext, and DES (K, P) is the DES
> encryption of P under key K.
> 
> The encryption then has three steps:
> 
> 	- XOR the input with K3
> 	- DES encrypt that with K2
> 	- XOR the result with K1
> 
> The first and last steps are called "whitening" because by xoring with
> a random value, any structure is destroyed.  White light is a uniform
> and unstructured mixture of all colors.
> 

	Anybody have any estimate as to how much actual strength this
adds to DES ?  How would one break it in a practical cracker machine ?





-- 
	Dave Emery N1PRE,  die@die.com  DIE Consulting, Weston, Mass. 
PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2  5D 27 BD B0 24 88 C3 18