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Re: [TLS] The PAKE question and PSK

Nico Williams <nico@cryptonector.com> Wed, 02 April 2014 16:13 UTC

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Date: Wed, 02 Apr 2014 11:12:11 -0500
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From: Nico Williams <nico@cryptonector.com>
To: Watson Ladd <watsonbladd@gmail.com>
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Subject: Re: [TLS] The PAKE question and PSK
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On Tue, Apr 1, 2014 at 11:28 PM, Watson Ladd <watsonbladd@gmail.com> wrote:
> The intended usecase is provisioning of constrained devices. While one
> could include a 128 bit key on each device and have users type it in
> (as they do for Xbox Live and Windows verification: 25 letters and
> numbers from a 32 bit alphabet) it was felt that this was a bit much.
> PSK will not work with anything that isn't a key, because offline
> attack works beautifully. Nico's concerns about key database
> compromise, etc, are ignoring the realities of this setting: the
> password is the least valuable thing on the device, and since it was
> not entered by the user (as the device has no user interaction
> capability) unlikely to be reused.

Ah, thanks for clarifying the context.  I agree that in this context a
ZKPP, unaugmented, is just fine.  If I had to build one today I'd use
EKE with a DJB cuve and Elligator: no patents apply and none are
likely to apply (EKE's patent is expired, and it seems exceedingly
unlikely that any patent covers the rest).

Nico
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