Re: preliminary version of counter mode draft

[Jack Lloyd <lloyd%acm.jhu.edu@localhost>]

On Wed, 19 Mar 2003, Bill Sommerfeld wrote:

Just a comment from a non-implementor lurker.

>    3) Which ciphers do people want to use (AES, 3DES, Twofish, etc.)?

I'm curious why all of these were here:

>      twofish128-ctr   RECOMMENDED       Twofish in SDCTR mode,
>                                         with 128-bit key
>      twofish192-ctr   OPTIONAL          Twofish with 192-bit key
>      twofish256-ctr   OPTIONAL          Twofish with 256-bit key
>      serpent128-ctr   RECOMMENDED       Serpent in SDCTR mode, with
>                                         with 128-bit key
>      serpent192-ctr   OPTIONAL          Serpent with 192-bit key
>      serpent256-ctr   OPTIONAL          Serpent with 256-bit key

Serpent and Twofish treat 128, 192 and 256 bit keys basically the same
anyway (unlike AES, where all three different versions might be useful).
Obviously there is no reason _not to have them all (besides a fairly small
amount of extra work for implementors), but it seems pointless, given that
serpent256-ctr and twofish256-ctr would do the job of all six of these just
fine.

-Jack