Re: Review of draft-manral-ipsec-rfc4305-bis-errata-02.txt

On Mon, 11 Dec 2006 09:55:33 -0600
Nicolas Williams <Nicolas.Williams@sun.com> wrote:

> Also, I'm not sure that the use of "MUST-" and "SHOULD+" is actually
> useful.  In this update no algorithms previously classified as MUST-
> have been downgraded, and no algorithms previously classified as
> SHOULD+ have been upgraded.  It seems likely to me some AES cipher
> mode will eventually become a MUST, but it's not clear to me that
> AES-CBC, for example, which is marked SHOULD+, will be it.  Therefore
> I would argue that these designations should be changed to MUST and
> SHOULD, respectively.  Or perhaps this I-D is a good opportunity to
> downgrade TripleDES-CBC to SHOULD or MAY and upgrade either AES-CBC
> and/or AES-CTR to MUST?
> 

I'm not sure it's feasible yet to make 3DES a SHOULD; it's quite clear
to me that AES-CBC should become a MUST.  We can't make AES-CTR the
only MUST unless we abolish manual keying.  I could probably deal with
AES-CTR and AES-CBC both being mandated, but I'm really not a fan of
counter mode; it's just too easy to make bad mistakes.

		--Steve Bellovin, http://www.cs.columbia.edu/~smb

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