Subject: Secure DNS is just weakly secure

From: Masataka Ohta <[email-masked]>
Date: Tue, 14 Mar 2006 11:18:28 +0900

For those of you who are vigorously working on secure DNS,
it should be noted that secure DNS is just weakly secure.

Weak security, in general, means just blindly believe
infrastructure is secure.

As you know, plain DNS is weakly secure just blindly believing
infrastructures of ISPs and registries (and registrars) along
with their directors and employees secure.

If some ISP between you and your peer betrays you, your record
can be forged by, say, rewriting your reply.

If some registry between you and your peer betrays you, your
record can be forged by, say, redirection to wrong NS addresses.

There are numerous ways to hide the forgery from casual
inspection by you.

Fortunately, weak security is just enough for most purposes
that we can live with plain DNS.

Instead, if you use secure DNS, you no longer believe ISP
infrastructure secure but still believe registries secure.

If some registry between you and your peer betrays you, your
record can be forged by, say, redirection to wrong NS addresses
with forged certificates and forged signatures.

There are numerous ways to hide the forgery from casual
inspection by you.

That is, secure DNS is just weakly secure.

Fortunately, weak security is just enough for most purposes
that we can live with secure DNS.

But, why do you bother?

						Masataka Ohta

PS

In general, PKI (public key cryptography with third party CAs)
is just weakly secure.

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From: Chris Thompson <[email-masked]>
Date: Tue, 14 Mar 2006 16:13:39 +0000 (GMT)

Masataka Ohta <[email-masked]> writes

> So, the conclusions in my original mail are:
> 

I suppose this represents progress, of a sort. You have argued in the
past that DNSSEC will be _less_ secure (because of the extra complexity
of the implementations).

> and the quesiton is:

I would like to address that question to you. It's not as though 
everyone following this list doesn't know that you think DNSSEC 
worthless, if not postively malign. I recall extended threads on 
the subject in Jan-Feb 2004, May-Jun 2004, Mar 2005.

Of course, you have every right to keep on reminding us of this. 
But I do wonder whether you feel you are actually making converts 
to your point of view. I see little sign of that on the list itself.

-- 
Chris Thompson               
University of Cambridge Computing Service,
Email: [email-masked]

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From: "Loomis, Rip" <[email-masked]>
Date: Wed, 15 Mar 2006 13:02:50 -0500

(I know that there have been requests to shut down this
thread, so my apologies for continuing it, but...)

> Secure DNS removes "control" of ISPs, which are as reliable as
> registries, but still leaves "control" of registries.

The assertion you make above is not only not provably
true, but is in my experience completely false.  Many providers
of recursive DNS service with which I deal on a regular basis
are *much* less reliable than the registries for DNS
information that I use on a regular basis.

And if you drop that assertion (since it's not generally
true) I don't think your argument sheds any useful light.
In particular, securing DNS based on shared keys (which
you appear to advocate) does not scale well at all and
has significant issues due to the inability to strongly
correlate a key with a particular individual (since it
is by definition shared with others).  And if one tries
to use public/private key pairs...well whaddaya know,
that's what DNSSEC is doing!  And yes, there are potential
issues if a DNSSEC signing key at a registry is
compromised--which is why that's an area of particular
interest for me (and others).  The good news is that there
are, in fact, technologies and procedures that can
address such issues.

This will be my last message to you in response to one of
these threads you occasionally start.  Thanks very much
for caring about securing DNS--I only wish that your efforts
to date had come up with a useful way to address the real
(but not fatal) flaws in the DNSSEC extensions as they
stand today.  I invite you to either propose an actual
valid alternative or contribute on updates to the existing
RFCs.

  --Rip