Subject: [homenet] write up of time without clocks

From: Michael Richardson <[email-masked]>
Date: Mon, 31 Oct 2016 09:36:49 -0400

Hi, I know that we talked a lot (especially Dave Taht) about how CPE devices
without RTCs could verify certificates and DNSSEC when they don't know the
time, and they won't know the time until they securely find an NTP server.

But, we talked about how this wasn't a totally catch-22, that we could
know how it was "at least" some time based upon file timestamp, or
self-certificate not-before dates, or do DNSSEC without time validation
first.

My question is: did this get captured into document somewhere?

--
Michael Richardson <[email-masked]>, Sandelman Software Works
 -= IPv6 IoT consulting =-

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From: Stephen Farrell <[email-masked]>
Date: Mon, 31 Oct 2016 13:39:21 +0000

> My question is: did this get captured into document somewhere?

This [1] seems relevant. I've not looked into it in
detail, but I'm guessing it has to be similar to the
above ideas.

S.

[1] https://roughtime.googlesource.com/roughtime

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From: Michael Richardson <[email-masked]>
Date: Mon, 31 Oct 2016 15:12:59 -0400

mcr> Hi, I know that we talked a lot (especially Dave Taht) about how CPE
mcr> devices without RTCs could verify certificates and DNSSEC when they
mcr> don't know the time, and they won't know the time until they securely
mcr> find an NTP server.

mcr> But, we talked about how this wasn't a totally catch-22, that we could
mcr> know how it was "at least" some time based upon file timestamp, or
mcr> self-certificate not-before dates, or do DNSSEC without time validation
mcr> first.

mcr> My question is: did this get captured into document somewhere?

Stephen Farrell <[email-masked]> wrote privately to inform me
about https://roughtime.googlesource.com/roughtime.

So, this is a network protocol to essentially crowd-surf the correct time
via signed replies of nonces.  It has a way to generate enough signatures
fast enough to not get DDoS on a 10G link.

I'm not sure how the client trusts the RoughTime servers' certificates, or if
that matters given the distributed nature of things (TOFU would work).

I'm not looking for a network protocol, because the devices I care about do
not (yet) have network!  I'm looking for the write up a heuristic that says
that if you have local information that time was once verified to be at X,
that it must be at least >X.

==== aside:

Interesting in the protocol, it says:
            Since we require that requests be padded to 1KB to avoid becoming
            a DDoS amplifier, a 10Gbps network link could only deliver 1.2
            million requests per second anyway.

I'm been thinking that this might be the only way to deal with (UDP) DDoS with
potentially forgable source addresses: insist that the sender's packet is
always at least as big as the reply they want.