I just spent the last half hour or so looking at the description of
the public-key authentication scheme (or is it schemes?) used by
version 4 of the Reference Implementation of NTP, on ntp.org.
Unfortunately, this documentation seems to range in quality from
"bizarre" to "unintelligible", and the behavior of the "ntp-keygen"
program does not make it clearer.

The question is: is there any better documentation, from which I would
be able to discern whether NTP public-key authentication truly is that
bizarre (and, if I have vaguely understood what I read, entirely
broken with respect to PKI) or simply poorly-documented.

(I'm not a complete idiot where PKI stuff is concerned, having written
two CA implementations, but I'm barely able to make head or tail of
the "official" documentation.  The FAQ seems to just regurgitate the
command lines from the official documents without any sort of
explanation at all.)

-GAWollman

-- 
Garrett A. Wollman    | As the Constitution endures, persons in every
wollman@csail.mit.edu | generation can invoke its principles in their own
Opinions not those    | search for greater freedom.
of MIT or CSAIL.      | - A. Kennedy, Lawrence v. Texas, 539 U.S. 558 (2003)

At 9:33 PM +0000 2005-07-15, Garrett Wollman wrote:

> The question is: is there any better documentation, from which I would
> be able to discern whether NTP public-key authentication truly is that
> bizarre (and, if I have vaguely understood what I read, entirely
> broken with respect to PKI) or simply poorly-documented.

	As far as autokey is concerned, the best stuff I know of is at 
<http://ntp.isc.org/bin/view/Support/ConfiguringAutokey>, created by 
Steve Kostecke based on his real-world experience.

-- 
Brad Knowles, <brad@stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

 -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
 Assembly to the Governor, November 11, 1755

 SAGE member since 1995. See <http://www.sage.org/> for more info.
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Garrett Wollman wrote:
> I just spent the last half hour or so looking at the description of
> the public-key authentication scheme (or is it schemes?) used by
> version 4 of the Reference Implementation of NTP, on ntp.org.
> Unfortunately, this documentation seems to range in quality from
> "bizarre" to "unintelligible", and the behavior of the "ntp-keygen"
> program does not make it clearer.
> 
> The question is: is there any better documentation, from which I would
> be able to discern whether NTP public-key authentication truly is that
> bizarre (and, if I have vaguely understood what I read, entirely
> broken with respect to PKI) or simply poorly-documented.
> 
> (I'm not a complete idiot where PKI stuff is concerned, having written
> two CA implementations, but I'm barely able to make head or tail of
> the "official" documentation. The FAQ seems to just regurgitate the
> command lines from the official documents without any sort of
> explanation at all.)
> 
> -GAWollman
> 

Garrett, was this: http://www.eecis.udel.edu/~mills/ntp/html/authopt.html
the documentation you looked at?

There are also 3 documents listed on Dave's ntp pages at:
http://www.eecis.udel.edu/~mills/ntp.html

which discuss NTP Security Model, NTP Security Algorithms and NTP 
Security Protocol. These may prove more useful to you if you haven't 
seen them. Great, I just checked and they're not there now. I do have at 
least one of these documents that I can send you separately. I can also 
send you a paper by Matt Bishop that I found.

Danny



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Garrett,

If you are talking about Dave's documentation I believe he will be open to
improvments after he is done writing The Book, in September.

If you are talking about stuff at ntp.isc.org, we can correct that even
sooner.  I would be thrilled to have folks help out with improving the
documentation at ntp.isc.org.

Also, I am working on converting various programs in the distribution to
Bruce Korb's AutoGen system, which will give us better options processing as
well as (IMO) an easier time with program and file documentation.

"Today" I am looking in to options processing; "Tomorrow" I'll start on the
documentation.  My intent on the the AutoGen documentation is to avoid
stepping on Dave's toes.

Please see:

 http://ntp.isc.org/bin/view/Dev/GNUAutoGenConversion

for more information.

H

On 2005-07-15, Garrett Wollman <wollman@khavrinen.csail.mit.edu> wrote:

> The question is: is there any better documentation, from which I would
> be able to discern whether NTP public-key authentication truly is that
> bizarre (and, if I have vaguely understood what I read, entirely
> broken with respect to PKI) or simply poorly-documented.

You may want to take a look at
http://www.eecis.udel.edu/~mills/database/reports/stime/stime.pdf

> The FAQ seems to just regurgitate the command lines from the official
> documents without any sort of explanation at all.

http://ntp.isc.org/bin/view/Support/ConfiguringAutokey is based on my
hands-on experience setting up NTP Authentication. It's an intentionally
terse step-by-step guide which is intended to complement Dr. Mills'
in-depth documentation.

-- 
Steve Kostecke <kostecke@ntp.isc.org>
NTP Public Services Project - http://ntp.isc.org/