Re: [psg.com #460] IESG - Transport - Oakley

[Jeffrey Hutzelman <jhutz%cmu.edu@localhost>]

On Monday, June 14, 2004 13:22:18 +0200 Niels Möller <nisse%lysator.liu.se@localhost> 
wrote:

> Jon Bright <jon%siliconcircus.com@localhost> writes:
>
> > Nonetheless, providing a hint to possibly-ill-informed implementors
> > about what should come first by default wouldn't be a bad thing?
>
> Adding such a recommendation would not be the end of the world as we
> know it, but it would be a useless bloat of the spec, imho. The
> protocol specification should explain the details needed for
> implementing the protocol, it's not the place for random advice on how
> to best use and implement the protocol.

Actually, the protocol specification is a perfectly reasonable place for 
advice to implementors.

> I think it should be fairly obvious that group14 is harder to crack
> than group1, and that using group14 will consume more cpu cycles.

Well, that's the expectation I would have.  But I don't agree it will be 
obvious to everyone.


In any case, I don't have any particular attachment to adding such a 
recommendation; I just tossed it out there as an idea.




> BTW, about naming. The proposed naming is a little confusing:
>
>   SSH name                      "Well known" name
>
>   diffie-hellman-group1-sha1    Well known group 2     (RFC 2412)
>                       ^                          ^
>   diffie-hellman-group14-sha1   Well known group 14    (RFC 3516)

Yup.  I blame the people who named diffie-hellman-group1-sha1.



> On the other hand,
> it would be nice to be able to generalize
>
>   diffie-hellman-groupXX-sha1   Well known group XX    (RFC 3516)

I was assuming it was pretty much agreed that this would be the appropriate 
solution.  It does mean there's no name for the method which uses group 1, 
but somehow I suspect we don't care very much...


Oh, and for those reading who are confused...
- Groups 1-4 are defined in RFC2409 (IKE) and RFC2412 (Oakley).
 Groups 1 and 2 are MODP groups of size 768 and 1024 bits, and
 are defined identically in both places.
 Groups 3 and 4 are EC2N groups; they are _not_ defined identically
 in both places -- one of the two documents is in error, but I'm not
 awake enough to tell which.
- Groups 5 and 14-18 are defined in RFC3526 (not RFC2516).  They
 are MODP groups of increasing size, from 1536 to 8192 bits.

-- Jeffrey T. Hutzelman (N3NHS) <jhutz+%cmu.edu@localhost>
  Sr. Research Systems Programmer
  School of Computer Science - Research Computing Facility
  Carnegie Mellon University - Pittsburgh, PA