Re: [Cfrg] draft-irtf-cfrg-eddsa -- one final proposal for domain separation (context labels) for ed25519

Ilari Liusvaara <ilariliusvaara@welho.com> Thu, 21 April 2016 14:38 UTC

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Date: Thu, 21 Apr 2016 17:37:53 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: David Jacobson <dmjacobson@sbcglobal.net>
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Subject: Re: [Cfrg] draft-irtf-cfrg-eddsa -- one final proposal for domain separation (context labels) for ed25519
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On Wed, Apr 20, 2016 at 10:47:04PM -0700, David Jacobson wrote:
> On 4/20/16 4:38 PM, Benjamin Kaduk wrote:
> >On Wed, 20 Apr 2016, Daniel Kahn Gillmor wrote:
> 
> If you want to include a NUL byte to separate the context from the following
> stuff, then to avoid ambiguity you need to require that the context not
> contain any NUL bytes.   And this rules out general binary blobs as context
> values, including general ASN.1 objects.

You really don't want ASN.1 objects, JSON serializations or anything like
that as context values.

Those values are supposed to be at most name of the protocol and possibly
version thereof (if one decides to use those at all).


-Ilari