Re: [DNSOP] New Version of draft-ietf-dnsop-algorithm-update-00: Algorithm Implementation Requirements and Usage Guidance for DNSSEC

Michael Sinatra <michael@brokendns.net> Tue, 27 March 2018 17:03 UTC

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To: Paul Hoffman <paul.hoffman@vpnc.org>
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From: Michael Sinatra <michael@brokendns.net>
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Date: Tue, 27 Mar 2018 10:21:59 -0700
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Subject: Re: [DNSOP] New Version of draft-ietf-dnsop-algorithm-update-00: Algorithm Implementation Requirements and Usage Guidance for DNSSEC
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On 03/27/18 05:43, Paul Hoffman wrote:
> On 26 Mar 2018, at 17:30, Michael Sinatra wrote:
> 
>> I am a bit uncomfortable with the document's disrecommendation of SHA384
>> and ECDSAP384SHA384.  The main reason for this is that for crypto
>> recommendations here in the USG,
> 
> Note that those are for encryption, where they want to keep some things
> secret for 40 or more years. DNSSEC is an authentication mechanism. If
> it takes two decades to break an P256 key that is used for encryption,
> the attacker gets much (much!) more value than breaking one that is used
> for authentication.

Agree, and I would even add that the limited signature validity interval
of DNSSEC makes ECDSAP256SHA256 more than "good enough" for DNSSEC.
However, my motivation is based on your next point...

> The fact that the NSA document is unclear on this point has been causing
> problems for many people, including for people inside the NSA.

My goal is to basically avoid confusion and just tell people to use the
strongest algorithm they can reasonably use.  I.e. follow the CNSA
recommendations and don't spend a lot of time thinking about the
application.

I'll try to come up with some wording for the draft (i.e. the sentence
that I was uncomfortable with) that captures the notion that
P-384/SHA384 doesn't add much in the way of security, but that there's
nothing wrong with "crypto maximalism" in this case, and see what the WG
thinks.

michael