Subject: [Hipsec] Storing ORCHIDs/HITs under a /28

From: Julien Laganier <[email-masked]>
Date: Fri, 2 Jun 2006 14:28:17 +0200

Folks,

The proposed ORCHID prefix length of 8-bits has been discussed on both 
HIPsec and int-area ML. Some persons have objected that allocation 
because they believe an 8-bits prefix is too short by some. We had an 
offline discussion in the hope to find a solution acceptable for both 
parties, and we eventually agreed that allocation of a /28 is the way 
to move forward. 

Therefore, I'd like to confirm with the HIP WG that storing ORCHIDs 
(hence HITs) under a /28 prefix is acceptable. The implication is 
that the public key hash would be truncated to 100-bits.

If you agree or disagree with that proposal, please say so ASAP (say 
before next Friday, the 9th) so we can move forward and resubmit the 
ORCHID draft before the cut-off.

Thanks,

--julien

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From: Tim Shepard <[email-masked]>
Date: Fri, 02 Jun 2006 09:16:07 -0400

> that the public key hash would be truncated to 100-bits.

("storing" seems like a poor choice for a verb here.)

I find the /28 prefix to be inexplicably long.

I can understand that someone might object to a prefix length of /8,
but how that objection continued until 20 more bits had been added to
the prefix, well, I really wonder.

Please explain.

(How many random 100-bit strings have to be generated before the
 probability of a duplication has crossed over the one-in-a-million
 threshold?  I'll try to estimate this sometime this weekend.)

			-Tim Shepard
			 [email-masked]

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From: Julien Laganier <[email-masked]>
Date: Fri, 2 Jun 2006 16:05:25 +0200

On Friday 02 June 2006 15:16, Tim Shepard wrote:
> > Therefore, I'd like to confirm with the HIP WG that storing
> > ORCHIDs (hence HITs) under a /28 prefix is acceptable. The
> > implication is that the public key hash would be truncated to
> > 100-bits.
>

Ok, feel free to enlighten us if you have a better term. I am too busy 
to do trichotetratomy right now :-> 

> I can understand that someone might object to a prefix length of
> /8, but how that objection continued until 20 more bits had been
> added to the prefix, well, I really wonder.
>
> Please explain.

We'd like this allocation to be made as an IETF experimental 
allocation performed by the IANA. IANA has a /23 allocated for that 
purpose, so our prefix has to be strictly longer than 23, or more (We 
cannot reasonably ask for say half of the available space.) 

Given that, 28 seemed sensible.

>  threshold?  I'll try to estimate this sometime this weekend.)

Remember that this is an experimental prefix allocation. If the 
experiment is successfull we might be able to request for a larger 
allocation later on. 

Regarding the collision risk, it looks like the birthday paradox. 
Wikipedia gives this formula (I didn't spent time to verify the 
maths): 

n(p) ~ sqr(2 x N x ln( 1 / (1 - p) ) )

Where:
- N is the number of different birthdays (2^100 in our case)
- p is a fixed probability (1/1000000 in our case)
- p(n) is the probability that a duplicate occurs amongst a population 
of size n which has uniformly distributed birthdays.
- n(p) the smallest n for which the probability p(n) is greater than 
the given p

Result is that n(1/1000000) = 1590 billions. Seems okay to me for a 
time limited experiment.

--julien

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From: Julien Laganier <[email-masked]>
Date: Fri, 2 Jun 2006 16:05:25 +0200

Where:

--julien

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From: Julien Laganier <[email-masked]>
Date: Fri, 2 Jun 2006 16:05:25 +0200

Where:

--julien

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From: Julien Laganier <[email-masked]>
Date: Fri, 2 Jun 2006 16:05:25 +0200

Where:

--julien

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From: Tim Shepard <[email-masked]>
Date: Fri, 02 Jun 2006 10:11:25 -0400

> experiment is successfull we might be able to request for a larger 

This explanation helps much.  Thanks.

Sometimes experiments escape the laboratory and get popular faster
than the experimental version can be replaced with a version designed
to scale for the real world (e.g. IPv4).

			-Tim Shepard
			 [email-masked]

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From: Tim Shepard <[email-masked]>
Date: Fri, 02 Jun 2006 10:11:25 -0400

-Tim Shepard
			 [email-masked]

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From: Tim Shepard <[email-masked]>
Date: Fri, 02 Jun 2006 10:11:25 -0400

-Tim Shepard
			 [email-masked]

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From: Tim Shepard <[email-masked]>
Date: Fri, 02 Jun 2006 10:11:25 -0400

-Tim Shepard
			 [email-masked]

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From: Henrik Levkowetz <[email-masked]>
Date: Fri, 02 Jun 2006 20:20:01 +0200

>  threshold?  I'll try to estimate this sometime this weekend.)

Avid Terry Pratchett readers will know that one-in-a-million chances
come true nine times out of ten ,,,;-)

	Henrik

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From: Gonzalo Camarillo <[email-masked]>
Date: Fri, 02 Jun 2006 22:07:09 +0300

Hi,

just to be sure, if nobody screams before Friday June 9th on this 
mailing list, we are going to move forward with the /28 allocation. As 
soon as we resolve this, we will request the publication of the base 
spec and the esp draft. Shortly after that, we will request the 
publication of the rest of our current drafts, recharter, and start 
working officially on the new items.

Cheers,

Gonzalo