Re: [TLS] (selection criteria for crypto primitives) Re: sect571r1

Johannes Merkle <johannes.merkle@secunet.com> Tue, 21 July 2015 14:39 UTC

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Date: Tue, 21 Jul 2015 16:39:17 +0200
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Subject: Re: [TLS] (selection criteria for crypto primitives) Re: sect571r1
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Rene Struik schrieb am 16.07.2015 um 03:42:
> Dear colleagues:
> 
> It seems prudent to keep some diversity of the gene pool and not only have curves defined over prime curves. Similarly,
> one should perhaps have some diversity of gene pool criteria within the set of recommend curves and not only include
> special primes. Should some problem with a particular subclass show up over time, one then at least has other classes
> available.
> 
> On a general note, I do not understand what is wrong with having a dictionary of curves that is well-specified, but
> whose members are not all widely used. To my knowledge, having a dictionary does not force everyone to use every term in
> this (mandatory vs. optional to implement vs. mandatory to use, etc.).
> 
> If one follows the line of reasoning of some people on the mailing list earlier today, doesn't this also call into
> question Brainpool curves, or, e.g., the Misty cipher, etc.? Moreover, this certainly calls into question why one would
> have a whole set of new DLP groups (which certainly cannot be widely used yet, since the ink to write the parameters
> down is still wet). What about RSA-1024, etc.?
> 

I absolutely back up this position. Currently, the TLS 1.3 draft only permits curves over special primes. It has become
quite clear in the discussions in CFRG and at the NIST ECC workshop that some parties (major hardware manufacturers,
certification bodies) prefer curves over random primes. And as Rene has pointed out, allowing both would also give more
agility w.r.t potential future attacks on certain sub-classes.

Why can't the draft just specify the curves that are MTI but allow (at least some) alternative options, instead of
putting all our eggs in one basket?

Johannes