Re: [Curdle] Kathleen Moriarty's Yes on draft-ietf-curdle-ssh-dh-group-exchange-05: (with COMMENT)

[Spencer Dawkins at IETF <[e-mail]>]

So, Kathleen's ballot thread, but since she and I share this curiosity ...

On Fri, Sep 15, 2017 at 6:01 AM, Loganaden Velvindron <[e-mail]>
wrote:

> On Wed, Sep 13, 2017 at 10:08 PM, Kathleen Moriarty
> <[e-mail]> wrote:
> > Kathleen Moriarty has entered the following ballot position for
> > draft-ietf-curdle-ssh-dh-group-exchange-05: Yes
> >
> > When responding, please keep the subject line intact and reply to all
> > email addresses included in the To and CC lines. (Feel free to cut this
> > introductory paragraph, however.)
> >
> >
> > Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.
> html
> > for more information about IESG DISCUSS and COMMENT positions.
> >
> >
> > The document, along with other ballot positions, can be found here:
> > https://datatracker.ietf.org/doc/draft-ietf-curdle-ssh-dh-
> group-exchange/
> >
> >
> >
> > ----------------------------------------------------------------------
> > COMMENT:
> > ----------------------------------------------------------------------
> >
> > I do agree with Spencer, the text that is non-normative reads as if this
> is
> > fully deprecating any recommendation below 2048, but then the normative
> text
> > just says SHOULD.  Is there a reason this is not MUST?  I know
> deprecating
> > things takes a long time.
>
> Yes, it takes a long time, and also because of backward compatibility.
> We felt that "SHOULD" was sufficient at the time.


That doesn't surprise me (speaking only for myself).

It might be helpful to add a sentence explaining that the SHOULD is for
backward compatibility.

That changes the incentives a bit - implementers have more incentive to
implement a SHOULD if it's not a MUST *yet*, but when the community stops
worrying about backward compatibility, it could be, and then other
implementations won't interop with yours.

And, for extra credit, that could happen suddenly, if someone posts a
clever attack on 1024-bit keys that requires minimal computing resources
and includes an implementation that anyone can pick up ... so everyone else
stops accepting shorter keys, like, today.

But do the right thing, of course.

Spencer