Path: illuminati.io.com!nobody
From: ritter@indial1.io.com (Terry Frank Ritter)
Newsgroups: sci.crypt

Subject: DESX
Date: 6 Mar 1994 02:58:52 -0600
Organization: Illuminati Online
Lines: 42
Message-ID: <2lc60c$1u6@indial1.io.com>
NNTP-Posting-Host: indial1.io.com


 In <2ku9uc$sr8@msuinfo.cl.msu.edu> mrr@scss3.cl.msu.edu (Mark
 Riordan) writes:

>DESX is an encryption algorithm that extends the famous DES
>(Data Encryption Standard) algorithm to a keysize of 120 bits.
>It does this by simply XORing the input block with a bit pattern
>(pre-Whitening), encrypting with standard DES, and then XORing
>the result with another bit pattern (post-Whitening).


             A
             |
             v
      ka -> XOR
             |
             v
             B
             |
             v
      k1 -> DES
             |
             v
             C
             |
             v
      kb -> XOR
             |
             v
             D


 Single capital letters represent 64-bit blocks.  k1 is a 56-bit
 DES key.  ka and kb are 64-bit keys developed by hashing k1 and
 k2, a 64-bit key.  k1 and k2 total 120 bits.

 Presumably the salient issue is that the outside XOR's are
 intended to protect the internal DES from exhaustive search.

 ---
 Terry Ritter   ritter@io.com