G'day all. On Wed, Apr 23, 2003 at 06:08:11PM +1000, I wrote:
Codec.Encryption specifies what the module is for, not how it is used. Presumably there are going to be some type classes somewhere which specify whether it is a BinarySymmetricCipher like TripleDES or TextSymmetricCipher like FourWheelNavalEnigma.
My bad. DES is not even a codec. A cipher is an algorithm for turning an n-bit block into another n-bit (and back again) block using an m-bit key. It does not cover encoding messages longer or shorter than an n-bit block. At best it's a "codec" for a certain fixed-size binary object where the size depends, in general, on the algorithm. This table may help clarify the thinking: | Algorithm | Codec | Format ----------------+---------------+---------------+---------------- Cipher | DES | CBC-DES | SSL MAC | SHA-1 | HMAC-SHA-96 | SNMPv3 Text compress | LZ77 | Deflate | GZip Image compress | DCT | JPEG | JFIF My copy of OpenSSL, for example, supports at least nine "codecs" based on single-strength DES. Cheers, Andrew Bromage