Let's get moving on NTS

[Ian Bruene]

On 01/06/2019 02:55 PM, Gary E. Miller via devel wrote:
> Seems to me that Section 6 of the proposed RFC defines this pretty well.
> Once you can figure out who Clarlie (NTPD) and Delta (NTS-KE) are.

Partially. It gives an example of a way to do it, but no protocol or 
message scheme; just what the cookies could look like. It is missing the 
primary piece that you want in that section of the design.

> Hardly qualifies as a transaction as there is no reciprocity (See the
> dictionary).  In the dark past, either the NTPD told the NTS-KE what
> keys to use, or vice versa.  Not even a need for an ACK.

Fair enough, I'm not versed in the terminology here.

>> "It's whatever is needed to verify the cookie from Alpha."
> Yes, the blob as defined in Section 6.
>
>> Whatever needs to be communicated on that channel it can't be
>> verifying cookies and also be "only an occasional ???". Verifying
>> cookies means every single ntp packet that comes in to Charlie has to
>> be checked with Delta.
> Nope.  Reread the Proposed RFC.  NTS-KE and NTP agree before hand on
> some long lived keys to use.  They actually don't need to 'agree'.
> Either the NTS-KE tells the NTP, or vice versa.  Maybe no need for any
> negotiation.  Then use them for hours, days, weeks or months.
>
> Section 6 proposes a simple means to keep generating new short term
> keys fomr old keys, so no need for further communication between the
> NTS-KE and NTPD.  Just once is enough.
>
> Not to say that it can't, or shouldn't, get a bit more complicated, but
> it is not required.

Verifying /cookies/ would be NTPD asking NTS-KE for the data the cookie 
represents. The only reason to do that would be if NTPD never handles 
key storage / creation / ratcheting / etc itself and offloads all of 
that to NTS-KE.

That is the one option that has been universally shot down as bad. I've 
pushed an update to nts.adoc.

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