Re: draft-ietf-ipsec-ciph-aes-ctr-00.txt

["Housley, Russ" <[e-mail]>]

Hilarie:

Some people that have done implementations tell me otherwise.  Since I do 
not have firsthand experience, I will let them speak for themselves (if 
they are on this list).

Russ

At 09:55 PM 8/27/2002 -0600, The Purple Streak, Hilarie Orman wrote:
>AES decryption isn't all that different from encryption; the algorithm
>has only a minor difference and the rest is in tables.  Shouldn't
>really make any noticeable difference in code size or development time.
>
>Hilarie
>
>In due time, on Tue, 27 Aug 2002 at 16:56:59 -0400 Housley, Russ
>asserted:
>
> >  Steve:
>
> >  I disagree.  AES-CTR only uses the AES encrypt operation for both packet
> >  encryption and decryption.  Since AES encrypt and AES decrypt are quite
> >  different, unlike DES where they were nearly identical, there can be a
> >  considerable savings in code size and development time for AES-CTR since
> >  AES-CBC used both AES encrypt and decrypt operations.
>
> >  Russ
>
> >  At 08:40 AM 8/26/2002 -0400, Stephen Kent wrote:
> >  >At 3:23 PM -0400 8/24/02, Michael Richardson wrote:
> >  >>-----BEGIN PGP SIGNED MESSAGE-----
> >  >>
> >  >>
> >  >>>>>>>  "Alex" == Alex Alten <[e-mail]> writes:
> >  >>     >> Anyone who *needs* AES-CTR mode, likely needs it because 
> they have
> >  >>     >> >1Gb/s links they want to secure. As such, I think that they 
> have the
> >  >>     >> bandwidth not to care.
> >  >>
> >  >>     Alex> Micahael,
> >  >>
> >  >>     Alex> Are you implying that AES-CTR on a modern Intel CPU can 
> handle
> >  >> more
> >  >>     Alex> than 1 Gb/s Ethernet?  Is this because the IV stays in L1 
> cache?
> >  >>
> >  >>   I'm not making any claim about hardware or software implementations.
> >  >>My understanding is that AES-CTR mode is implemented more cheaply
> >  >>than AES-CBC mode. Whether this is hardware or software is simply a 
> question
> >  >>of what year it is.
> >  >
> >  >I don't think we can say that CTR mode is easier to implement in 
> software
> >  >than CBC mode. CTR mode probably isn't any faster than CBC, in 
> general, in
> >  >software, since software can't generally take advantage of the 
> pipelining
> >  >or parallelism.
> >  >
> >  >Steve