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Re: [kitten] SPAKE preauth: generation of SPAKE2 secret input

Benjamin Kaduk <kaduk@MIT.EDU> Thu, 14 May 2015 04:19 UTC

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Date: Thu, 14 May 2015 00:19:40 -0400
From: Benjamin Kaduk <kaduk@MIT.EDU>
To: Watson Ladd <watsonbladd@gmail.com>
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Cc: kitten@ietf.org
Subject: Re: [kitten] SPAKE preauth: generation of SPAKE2 secret input
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On Thu, 14 May 2015, Watson Ladd wrote:

> On May 13, 2015 9:05 AM, "Nico Williams" <nico@cryptonector.com> wrote:
> >
> >
> > That depends on how its salted.  For our purposes, in practice it's not.
>
> Not true: w comes from a much smaller list of values. If it was
> uniformly distributed over a wide range, we could use it as a key
> directly.

In the scheme kitten is considering, w is an existing kerberos long-term
(password-derived) key, so at least 128 bits and with no clear structure.

-Ben

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