Hal Murray <[email protected]> writes:

>Many security schemes get tangled up with time.  TLS has time limits on
>certificates.  That presents a chicken-egg problem for NTP when getting
>started.
>
>I'm looking for ideas, data, references, whatever?

For commercial CAs, the expiry time is a billing mechanism, not a security
mechanism.  A certificate is no more, or less, valid at 23:59:59 than it is at
00:00:01, no matter what the subscription renewal time in it says.  It's
fairly widespread practice in SCADA to completely ignore expiry times because
equipment that takes itself offline at 4am at a site six hours' drive away
because of an expired certificate is the last thing you want.

So set up the TLS connection, ignore the expiry time, perform your NTP update,
and then if necessary do the expiry check (unless it's SCADA gear, in which
case don't).  Nothing of value will be lost.

Peter.

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