Subject: Re: NSEC3 design FAQ

From: Ben Laurie <[email-masked]>
Date: Mon, 31 Oct 2005 12:49:27 +0000

Samuel Weiler wrote:
> Q: But why won't a single hash work?
> 
> A: Two reasons.
> 
>    The first: so long as the owner name of the NSEC3 RR's includes a
>    real name, the zone can be walked.  (This is true so long as the
>    owner name of the NSEC is obviously related to the QNAME (e.g. the
>    closest preceding existing name) -- having a real owner name
>    appear that is unrelated to the QNAME might work, but hasn't been
>    explored much.)
> 
>    The second: NSEC proofs wouldn't work.  NSEC (and NSEC3) proofs
>    both rely on the NSEC/NSEC3 specifying a range of names (or a range
>    of hashes) between which there are no records (or no records other
>    than delegations, for the 'delegation-only' or 'opt-in'
>    variations).  NSEC specifies a range of real names.  NSEC3
>    specifies a range of hashes.  Specifying one real name and one hash
>    does not specify a range, so a validator can't check whether a
>    QNAME is covered by such a record, hence whether or not the proof
>    is valid.

This seems incorrect - a real name plus a hash would work fine as a
range of hashes, from the hash of the real name to the other hash.

Cheers,

Ben.

-- 
http://www.apache-ssl.org/ben.html       http://www.thebunker.net/

"There is no limit to what a man can do or how far he can go if he
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From: Roy Arends <[email-masked]>
Date: Mon, 31 Oct 2005 14:17:21 +0100 (CET)

> range of hashes, from the hash of the real name to the other hash.

Your statment is correct, but this would leak too much info.

Since one name is leaked, it is trivial to do a binary search, hence 
enumerate the zone content.

Roy

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From: Ben Laurie <[email-masked]>
Date: Mon, 31 Oct 2005 13:54:51 +0000

> Your statment is correct, but this would leak too much info.

True, but that's the first reason.

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From: Roy Arends <[email-masked]>
Date: Mon, 31 Oct 2005 15:24:25 +0100 (CET)

> True, but that's the first reason.

Sorry to nit, but Sams first reason deals with ownernames. My statement is 
not restricted to ownernames. If a name (not hash) is present anywhere in 
the NSEC or NSEC3 record (ownername or RDATA), it can be walked.

Roy

---

From: Ben Laurie <[email-masked]>
Date: Mon, 31 Oct 2005 14:33:43 +0000

Roy Arends wrote:
> Sorry to nit, but Sams first reason deals with ownernames. My statement
> is not restricted to ownernames. If a name (not hash) is present
> anywhere in the NSEC or NSEC3 record (ownername or RDATA), it can be
> walked.

Sure, if you want to nit, nit away. My nit is that this is orthogonal to
my point, which is that name+hash works fine to specify a hash range.