From: "Karl A. Siil" <karl@geoplex.com>
Date: Tue, 23 Apr 1996 13:13:12 +0800
To: cypherpunks@toad.com
Subject: DES as a stream cipher
Message-ID: <2.2.32.19960422214547.006b636c@geoplex.com>
MIME-Version: 1.0
Content-Type: text/plain


Folks,

As this sounds like a previously solved problem, I wanted to find out about
using DES (or any block cipher) as a stream cipher, i.e., in a manner that
keeps input and output data length equal. I don't want to use a true stream
cipher, as I want to use the same key for multiple messages and stream
ciphers tend to place the bulk of their overhead in the re-key. Since stream
ciphers have "memory," I would have to "re-key" to the same key for each of
my messages. I would rather key something like DES once and run it in CBC
mode or use some other form of IV.

Help or pointers to help are greatly appreciated.

                                        Karl