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Re: [openpgp] Deprecate legacy hash algorithms

Jon Callas <joncallas@icloud.com> Fri, 17 March 2017 18:10 UTC

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From: Jon Callas <joncallas@icloud.com>
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Date: Fri, 17 Mar 2017 11:09:57 -0700
Cc: Jon Callas <joncallas@icloud.com>, openpgp@ietf.org
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To: Werner Koch <wk@gnupg.org>
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Subject: Re: [openpgp] Deprecate legacy hash algorithms
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> On Mar 17, 2017, at 2:00 AM, Werner Koch <wk@gnupg.org> wrote:
> 
> Hi,
> 
> Here is my suggestion on how to deprecate hash algorithms.  The new text
> is:
> 
>  Implementations MUST implement SHA-256.  Implementations MAY implement
>  other algorithms.  Implementations MUST NOT create messages which
>  require the use of SHA-1 with the exception of computing version 4 key
>  fingerprints and for purposes of the MDC packet.  Implementations MUST
>  NOT use MD5 or RIPE-MD/160.

My only comment is that if you're going to "deprecate" as opposed to "ban" then the term needs to be SHOULD NOT rather than MUST NOT. MUST NOT is a ban, not deprecation.

I prefer deprecation (SHOULD NOT) over banning (MUST NOT)  because a ban leads either to people being silly about a lack of backwards compatibility or they just defiantly ignore the ban. 

	Jon

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