On Mon, 22 Apr 1996, Karl A. Siil wrote:
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.
Have a look at cipher feed back mode. I have functions I call cfb64 in my DES library that give a 'single' character interface to cfb mode DES using 64bit feedback. This should be what you want. I also have a triple DES version of cfb64. In my SSL library also has cfb64 mode for IDEA. eric ftp://ftp/pub/Crypto/DES ftp://ftp/pub/Crypto/SSL http://www.psy.uq.oz.au/~ftp/Crypto -- Eric Young | Signature removed since it was generating AARNet: eay@mincom.oz.au | more followups than the message contents :-)