Re: [kitten] SPAKE Preauth

Nico Williams <nico@cryptonector.com> Sat, 02 May 2015 23:08 UTC

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Date: Sat, 2 May 2015 18:08:57 -0500
From: Nico Williams <nico@cryptonector.com>
To: Nathaniel McCallum <npmccallum@redhat.com>
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Subject: Re: [kitten] SPAKE Preauth
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On Fri, May 01, 2015 at 10:24:58PM -0400, Nathaniel McCallum wrote:
> On Fri, 2015-05-01 at 17:22 -0500, Nico Williams wrote:
> > Is there any reason that a generic one couldn't be specified here?
> 
> Speaking for myself, I want to create a high-quality integrated
> experience, not a generic one. I would prefer picking one open
> standard (such as OATH) and getting the details right. This is
> somewhat hard for me to quantify, but it arises from my experience
> implementing RFC 6560.

I don't buy this.  I understand and agree about how a dependency on
_FAST_ made RFC6560 difficult to deploy, and also how RFC6560's
incomplete/missing handling of *multiple* factors made it less useful
than expected.  I don't think that means "generality -> bad".

Also, I don't think a generic OTP 2nd factor here would necessarily lead
to a low-quality user experience.  For all user-input OTPs, all the user
needs is a prompt, which can be sent in UTF-8 and already localized to
a language of the user's preference (since the AS ought to know what
that might be).  I don't see how the user-input OTP experience can get
much better than that.

I suppose one could add media (a vine showing the act of pulling the OTP
out of one's pocket or purse, reading the OTP, then entering it on a
keyboard?  an audio description of the same?), but text is quite
accessible.

Nico
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