How to set time.

[Niels Elgaard Larsen]

Scott Bennett wrote:
>      On Thu, 23 Jul 2009 17:32:27 -0400 Niels Elgaard Larsen <elgaard at agol.dk>
> wrote:

>> Yes, that was why i suggested only using it to set the time zone by 
>> changing the clock a number of hours.
> 
>      I don't think that would be good enough to satisfy tor's requirements
> for time consistency.

No, but what i meant was that if the system time is wrong, there is a 
good chance that it is a time-zone mismatch in which case adjusting a 
clock a multiple number of ours should be safe.


>> Using an average of three entry-nodes could also work. Maybe add a 
>> little random time.
> 
>      Actually, no, three would not be enough, but statistical quality
> control of some sort would be necessary.  First off, this kind of thing
> should be a last resort option, not a common approach.

Well, if done right it could be a good way for the client to set it time.
...
>> GPS or DCF77 would be good, but requires hardware.
> 
>      Right.  Those are no good in this situation.

But GPS might be an option on e.g. Android platforms in the future.

>      Exactly.  Also, NTP is not encrypted, so an observer would know the
> set of time values from which one value would be used by the client.
>      Lest another point be forgotten, the methods of determining the correct
> time that we are discussing here would only be available in the case of
> client operations.  tor should still not set a clock or offset itself if
> it is to run as a relay.

No, but maybe a hidden node