Subject: Re: NSEC3 Issue 10: Potential DoS on Servers,

From: "David A. Wheeler" <[email-masked]>
Date: Wed, 21 Jun 2006 19:32:19 -0400 (EDT)

Earlier an "NSEC3 issue 10" was noted, saying:
>Significantly more work is required for a name server to
>respond to queries which require negative proofs using NSEC3
>than is required for a client to compose and send them.

I don't understand this as an issue, and I'm concerned that I may be
misunderstanding NSEC3.  It seems to me that the whole point
of the NSEC3 design is that all the hashes and signatures can
be precomputed, offline.  You don't want the signing key to BE on-line,
and you cannot assert that hash ranges don't exist until you've
computed ALL the valid hash values anyway. And the hash already includes
the salt, iterations, etc.  So I'd expect the entire chain of hash
calculations and signing to be done off-line, where DoS is irrelevant.

Thus, when a client sends a request, the server should be able to
trivially determine the non-match, find the relevant NSEC3 key
(a trivial binary search would be fine), and send the appropriate canned response.
The computation in view is very trivial; I wouldn't expect any complex computations
to be done for an NSEC3 response by a sensible name server (at run time).

Do I misunderstand things?  If so, please enlighten me!

--- David A. Wheeler 

--
to unsubscribe send a message to [email-masked] with
the word 'unsubscribe' in a single line as the message text body.
archive: <http://ops.ietf.org/lists/namedroppers/>