Re: [Cfrg] Adoption of draft-ladd-spake2 as a RG document

Watson Ladd <watsonbladd@gmail.com> Mon, 15 December 2014 18:47 UTC

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Date: Mon, 15 Dec 2014 10:47:20 -0800
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From: Watson Ladd <watsonbladd@gmail.com>
To: Dan Harkins <dharkins@lounge.org>
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Subject: Re: [Cfrg] Adoption of draft-ladd-spake2 as a RG document
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On Mon, Dec 15, 2014 at 10:19 AM, Dan Harkins <dharkins@lounge.org>; wrote:
>
>   Hello,
>
> On Sun, December 14, 2014 8:41 am, Alexey Melnikov wrote:
>> Hi,
>> This message starts 3 weeks adoption call for draft-ladd-spake2. Please
>> reply to this message or directly to CFRG chairs, stating one of the
>> following
>>
>> 1) that you are happy to adopt the draft as a starting point
>> 2) that you are not happy to adopt this draft
>> or
>> 3) that you think the document needs more work before the RG should
>> consider adopting it
>
>   I'm in favor of another PAKE being documented but I'm not sure
> why SPAKE2 is the one.
>
>> While detailed document reviews are generally welcome, this not a call to
>> provide detailed comments on the document.
>
>   SPAKE2 seems to be the Dual_EC_DRBG of PAKEs (and I'm very surprised
> the author isn't being accused by a bunch of people on twitter, and some
> hack tech blogger, of being an NSA plant out to subvert the Internet). There
> are 2 constant elements used in the calculation and knowledge of the scalar
> used to generate either of them would allow an attacker to break the
> exchange. This draft will need to go through a rigorous NUMS procedure in
> order to populate (the currently empty) section 3, a contentious step that
> other PAKEs would not need to go through.

Google has deployed this protocol with parameters generated by the
following code:
http://src.chromium.org/viewvc/chrome/trunk/src/crypto/p224_spake.cc

Do you see any way in which the discrete logarithm could be determined
from this or any other substantially similar procedure? If so, please
provide the procedure to this list, give us a week or two to think
about it, and then reveal the logarithm of the generated points.

>
>   There are other PAKEs out there so it would be nice to know why SPAKE2
> is the one that should be pursued.

I understand there is an AugPAKE draft already. But AugPAKE is
patented. There are alternatives, and I'm not committed to the
particular choice of PAKE: I've been informed of a few others to look
at and am examining them to see if they offer any advantages to
switch. I do think we need a PAKE with a solid security proof, and
several people have placed augmentation on the list of desiderata.

Sincerely,
Watson Ladd

>
>   regards,
>
>   Dan.
>
>
>
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