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Re: [DNSOP] RSASHA512 SHOULD-

Paul Wouters <paul@nohats.ca> Fri, 08 April 2016 14:18 UTC

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Date: Fri, 08 Apr 2016 10:18:06 -0400
From: Paul Wouters <paul@nohats.ca>
To: Francis Dupont <Francis.Dupont@fdupont.fr>
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Subject: Re: [DNSOP] RSASHA512 SHOULD-
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On Fri, 8 Apr 2016, Francis Dupont wrote:

> In draft-wouters-sury-dnsop-algorithm-update-01.txt the RSASHA512
> (code 10) DNSKEY/RRSIG algo got a SHOULD- for DNSSEC signing.
> The argument is it is not currently heavily used but I am afraid
> it is not a very good argument.
> I have a question for cryptographers in the list: as far as I know
> there is a relationship with the RSA key size and the output length
> of the hash algorithm. So perhaps we should not plan to move
> RSASHA512 to MAY (or worse to MUST NOT) as the SHOULD- means,
> i.e., put a SHOULD (vs SHOULD-) for RSASHA512?
> Note the time the I-D will be published and applicable we likely
> get a clearer view about this issue (:-)!

The reason behind our initial population of SHOULD- for RSASHA512 was
that:

- It is not used widely
- It causes much larger signatures for the same signature strength
   compared to the existing ECDSA algos and the imminent new EDDSA algos.

Paul

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