[ksk-change] Keeping two KSK keys long term

Michael StJohns msj at nthpermutation.com
Wed Oct 1 21:00:21 UTC 2014

On 10/1/2014 4:20 PM, Jakob Schlyter wrote:
> On 1 okt 2014, at 21:45, Paul Hoffman <paul.hoffman at vpnc.org> wrote:
>> It is my impression that having two (or more) KSK keys long term makes 5011 rollovers a bit less problematic, but I could be misunderstanding some of the subtleties of 5011 when mixed with draft-ietf-dnsop-dnssec-key-timing.
> Have two keys, and replacing one with another will keep the response sizes about the same over time (given that the key algorithm and size are the same), but other than that I haven't heard this.
> Perhaps Mike can clarify?

The contents of the root DNSKEY RRSet do not have to include all the 
trust anchors.  One of the things that struck me during the recent 
discussion is "why didn't they generate multiple trust anchor key pairs 
and provide that data during the initial bootstrap process (e.g. on the 
ICANN website) even if they only used one to sign"?

A new trust anchor can be added simply by being present in the root 
DNSKEY RRSet  (RDR!) signed by any existing trust anchor key for at 
least the Add Holddown time.  Once present in the trust anchor key set, 
it need not be present in the RDR unless its actually being used to sign 

Having two keys - in the trust anchor set -  should be the minimum 
steady state.  It means that you can compromise one of them and still 
recover without needing to do a full trust reboot.  It's not that the 
presence of multiple keys makes rollover less problematic exactly, but 
that it makes recovery from emergency revocations due to compromise 
possible as well as automated scheduled routine key changes.  Of course, 
this all depends on assumptions and operating procedures.  For example, 
If  its possible compromise both keys by breaking into the same box 
once, you obviously don't gain the protection.


> 	jakob
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