Re: [IPsec] review of draft-ietf-ipsecme-aes-ctr-ikev2-02

[Sean Shen <[e-mail]>]

Section 2.2 says that "AES MUST use different rounds for each of the key
sizes: ...".
The draft is not trying to say that IKEv2 requires 10/12/14 rounds for
128/192/256 key lengths. The draft is not trying to say that AES-CTR
requires 10/12/14 rounds for 128/192/256 key lengths.

Sean


2009/10/22 Paul Koning <[e-mail]>

>  AES is an algorithm with one parameter: the key length.  Based on that
> parameter various things change inside the algorithm.  It so happens that
> AES has rounds, and the number of rounds is a function of the key length.
> But as Tero says, that’s irrelevant to users of AES.  Any mention of rounds
> and other internal stuff belongs in exactly one place, the AES
> specification.  It does NOT belong in any specs that are merely users of AES
> – such as the AES-CTR spec.  It isn’t a characteristic of aes-ctr.
>
>
>
> Are you saying that people were arguing otherwise, that rounds need to be
> mentioned in the aes-ctr spec?  I strongly disagree; I can’t imagine any
> reason why that would be a good idea.
>
>
>
>                 paul
>
>
>
> *From:* [e-mail] [mailto:[e-mail]] *On Behalf
> Of *Shen Sean
> *Sent:* Wednesday, October 21, 2009 9:23 PM
> *To:* Tero Kivinen
> *Cc:* [e-mail]; Alfred HÎnes;
> [e-mail]
> *Subject:* Re: [IPsec] review of draft-ietf-ipsecme-aes-ctr-ikev2-02
>
> …
>
>  [Sean] I have no doubt that most users or vendors won't bother to choose
> or change what's already in crypto lib. But, a standard related document is
> responsible to clearly state what are necessary for a product, in this case,
> the basic characteristics of AES-CTR, even though some of these seems
> obvious. I remmeber the very early version of this document does not include
> rounds stuff, but eventually we added it based on reviewers' comments and
> requests.
>
>
>
>
>