Re: [TLS] SHA-3 in SignatureScheme

Eric Rescorla <ekr@rtfm.com> Fri, 02 September 2016 19:02 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Fri, 2 Sep 2016 12:01:56 -0700
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To: Yoav Nir <ynir.ietf@gmail.com>
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Subject: Re: [TLS] SHA-3 in SignatureScheme
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On Fri, Sep 2, 2016 at 11:38 AM, Yoav Nir <ynir.ietf@gmail.com> wrote:

>
> > On 2 Sep 2016, at 8:27 PM, Hubert Kario <hkario@redhat.com> wrote:
> >
> > On Friday, 2 September 2016 12:06:55 CEST Benjamin Kaduk wrote:
> >> On 09/02/2016 12:04 PM, Eric Rescorla wrote:
> >>> On Fri, Sep 2, 2016 at 8:25 AM, Dave Garrett <davemgarrett@gmail.com
> >>>
> >>> <mailto:davemgarrett@gmail.com>> wrote:
> >>>    On Friday, September 02, 2016 07:32:06 am Eric Rescorla wrote:
> >>>> On Fri, Sep 2, 2016 at 3:42 AM, Ilari Liusvaara
> >>>
> >>>    <ilariliusvaara@welho.com <mailto:ilariliusvaara@welho.com>> wrote:
> >>>>> I also don't see why this should be in TLS 1.3 spec, instead of
> >>>>> being
> >>>>> its own spec (I looked up how much process BS it would be to
> >>>
> >>>    get the
> >>>
> >>>>> needed registrations: informative RFC would do).
> >>>>
> >>>> I also am not following why we need to do this now. The reason
> >>>
> >>>    we defined SHA-2 in
> >>>
> >>>> a new RFC was because (a) SHA-1 was looking weak and (b) we had
> >>>
> >>>    to make significant
> >>>
> >>>> changes to TLS to allow the use of SHA-2. This does not seem to
> >>>
> >>>    be that case.
> >>>
> >>>    I don't think we strictly _need_ to do this now, however I think
> >>>    it's a good idea given that we'll need to do it eventually
> >>>
> >>> I'm not sure that that's true.
> >>
> >> Predicting future needs is not always reliable, yes.
> >>
> >>> From a release-engineering (standards-engineering?) perspective, I
> still
> >>
> >> don't see any reasons to add it now, and do see reasons to not add it
> now.
> >
> > what would be the reasons not to add it now?
>
> Several reasons:
>  - This is a core spec. Those don’t traditionally specify new algorithms
> unless they’re MTI (like SHA-256 is TLS 1.2 and RSAPSS here)
>  - For now, SHA-3 is yet another national algorithm. Why add this and not
> Streebog? [1]
>

I'm 100% in favor of adding any algorithm called Streebog. Also, perhaps
Orcslayer.

-Ekr


>  - Who’s to tell whether SHA-2 breaks earlier than SHA-3?
>
> So absent a desire to change MTI algorithms, I think publishing a “SHA-3
> and its use in TLS/IPsec/SSH/other” document is a fine idea, but not as
> part of any core protocol.
>
> Yoav
>
> [1] I’m sure there are excellent reasons why SHA-3 is better. We don’t
> just add any national standard unless we think we need it.
>
>
>
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