[ntpwg] Antw: Re: Antw: Re: Antw: Re: call for adoption (draft-dfranke-ntp-data-minimization)

["Ulrich Windl" <[e-mail]>]

>>> Ulrich Windl schrieb am 29.03.2017 um 08:26 in Nachricht <58DB53AC.69E : 161 :
60728>:
>>>> Harlan Stenn <[e-mail]> schrieb am 29.03.2017 um 01:23 in Nachricht
> <[e-mail]>:
> 
> > 
> > On 3/28/2017 7:08 AM, Daniel Franke wrote:
> >> On 3/28/17, Ulrich Windl <[e-mail]> wrote:
> >>> IMHO it would be consistent to set precision to 3 (the lowest possible
> >>> precision (0.125s) where NTP will start to work) and use 29 bits of
> >>> randomness then. Still a half billion attack packets might transit without
> >>> being detected, but I doubt that.
> > 
> > Ulrich, a precision of 3 is 8 seconds.
> 
> Harlan,
> 
> you are right, I missed the fact that a signed 24-bit number is used. I 
> forgot about the fact that any real life clock using NTP could have a 
> precision > 0. Of course I meant -3.

Oops: (Still suffering from DST switch): 8 bit, not 24, of course.

> 
> Regards,
> Ulrich
> 
> 
> > 
> >> 2**29 packets is about 541 gigabits including ethernet headers, so on
> >> a 1Gbps link is about a 0.18% chance of attacker success during the 1s
> >> MAXDIST window. On a 10Gbps link this becomes 1.8%. That's a big
> >> improvement over the status quo but still a non-negligible weakness.
> > 
> > Daniel, you're continuing to focus on and assume that:
> > 
> > - nobody will notice or care about these spoofs.  The reference
> > implementation from NTF/ntp.org reports these on both the client and the
> > server side.
> > 
> > - Once the client receives the response from the server, the origin
> > timestamp is zeroed in the client so no more responses from the server
> > will be accepted.
> > 
> > This has all been said before, several times, and you continue to ignore
> > these points.
> > 
> > Please take a breath of fresh air.
> > 
> >> What's the benefit of randomizing anything less than the full 64 bits?
> > 
> > For extranet communications, I'd likely choose 64 bits.  But I'd also
> > consider this to be *my* policy choice.  If somebody has good reason to
> > pick a different number, they should be able to.
> > 
> > I would generally not choose information hiding or extra randomizing on
> > internal NTP traffic.
> > 
> > -- 
> > Harlan Stenn <[e-mail]>
> > http://networktimefoundation.org - be a member!
> > 
> > _______________________________________________
> > ntpwg mailing list
> > [e-mail] 
> > http://lists.ntp.org/listinfo/ntpwg 
> 
> 
> 
> 




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