Re: [DNSOP] New draft: Algorithm Negotiation in DNSSEC

Stephane Bortzmeyer <bortzmeyer@nic.fr> Thu, 20 July 2017 07:57 UTC

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Date: Thu, 20 Jul 2017 09:51:45 +0200
From: Stephane Bortzmeyer <bortzmeyer@nic.fr>
To: Shumon Huque <shuque@gmail.com>
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Subject: Re: [DNSOP] New draft: Algorithm Negotiation in DNSSEC
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On Wed, Jul 19, 2017 at 02:28:37PM +0200,
 Shumon Huque <shuque@gmail.com> wrote 
 a message of 153 lines which said:

> > Suppose I send the list ECDSA;RSA, and I receive only ECDSA
> > signatures. How the resolver/cache would now if it was a complete
> > list?
> 
> The response contains the EDNS0 option if the responder executed
> this protocol. In which case, the cache would tag this response as a
> subset.

Sorry, I still do not understand. The EDNS0 option does not indicate
if the set is a subset or not. Or do you assume that, if the response
indicates that the responder executes this protocol, an answer is
always a subset (even if it's not)?

> When the resolver queries the DNSKEY RRset for the zone, it knows
> which algorithms are supported for the zone.

You can have keys which are not used for signing (such as in the root
today).