Subject: Re: dictionary attack on nameservers

From: Simon Josefsson <[email-masked]>
Date: Thu, 09 Sep 2004 11:18:52 +0200

Roy Arends <[email-masked]> writes:

> Hi,
>
> I'd like to fix NSEC name leakage in order to make zone enumeration with
> DNSSEC not easier then without DNSSEC.
>
> Not at any cost though, it would be nice if we can satisfy most/all of the
> following requirements (stolen from Ed's mail, thanks Ed)
>
> Prove non-existence of name/type without
>
>  - leaking names
>  - introducing fake names
>  - on-demand cryptographic operations
>  - being vulnerable to replay attacks
>  - incompatible changes with current DNSSEC
>
> Satisfying all requirements seems hard. If we can prioritise them, we've
> come a long way.

For those discussions, perhaps it is useful to explain all your
requirements in, e.g., http://www.links.org/dnssec/requirements.txt so
we at least start from a common understanding of the requirements.

I still don't understand the importance of the second requirement
above, and would like to have it explained in detail in a document,
rather than trying to collect various pieces of the picture from many
e-mails.

Keith Moore recently said something worth repeating, on the general
topic of requirements:

  Aside: I generally find it unhelpful to enumerate "requirements" because
  these things have different degrees of importance.  There's nothing
  wrong with enumerating "goals" or enumerating "problems" to be solved,
  but calling them "requirements" makes it seem that they're
  non-negotiable and all of equal importance.  We'd probably be happy with
  a partial solution - one that solved the worst of the problems without
  introducing harmful unintended effects -, and we probably won't find a
  complete solution anyway.

Thanks,
Simon

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---

From: Roy Arends <[email-masked]>
Date: Thu, 9 Sep 2004 11:32:13 +0200 (CEST)

> we at least start from a common understanding of the requirements.

perhaps, but I was doing the 20-lines dance to sing my current
thinking.

Roy