RE: Two AES encryption modes?

[Paul Koning <pkoning@equallogic.com>]

Excerpt of message (sent 24 July 2002) by Gregory Lebovitz:
> If AES-CTR comes to fruition quickly, can someone put forth an argument for
> continuing to use AES-CBC? 
> 
> (To clarify, I am not challenging us to drop AES-CBC, I just want to hear
> cryptographers explain why we would/would not need both).

Several possible reasons:

1. You have hardware that implements AES-CBC but not AES-CTR.
2. You want to use manual keying and therefore may send more than one
   packet with the same IV.  With CBC that doesn't compromise the
   confidentiality of the data; with counter mode it does.

In my view, #1 is a sufficient reason.

   paul