[RFC PATCH 4/7] crypto: remove ARC4 support from the skcipher API

[Eric Biggers]

[+linux-wireless, Marcel Holtmann, and Denis Kenzior]

On Thu, Jul 02, 2020 at 12:19:44PM +0200, Ard Biesheuvel wrote:
> Remove the generic ecb(arc4) skcipher, which is slightly cumbersome from
> a maintenance perspective, since it does not quite behave like other
> skciphers do in terms of key vs IV lifetime. Since we are leaving the
> library interface in place, which is used by the various WEP and TKIP
> implementations we have in the tree, we can safely drop this code now
> it no longer has any users.
> 
> Signed-off-by: Ard Biesheuvel <ardb at kernel.org>

Last year there was a discussion where it was mentioned that iwd uses
"ecb(arc4)" via AF_ALG.  So can we really remove it yet?
See https://lkml.kernel.org/r/97BB95F6-4A4C-4984-9EAB-6069E19B4A4F@holtmann.org
Note that the code isn't in "iwd" itself but rather in "libell" which iwd
depends on: https://git.kernel.org/pub/scm/libs/ell/ell.git/

Apparently it also uses md4 and ecb(des) too.

Marcel and Denis, what's your deprecation plan for these obsolete and insecure
algorithms?

- Eric