Subject: RE: [Design] Re: the KEY debate

From: "Hallam-Baker, Phillip" <[email-masked]>
Date: Thu, 8 Aug 2002 11:06:13 -0700

I don't think that the allegations of FUD are justified, however it is clear
that this group does not have a clear understanding of the security issues
surrounding key distribution.

Single point of failure sounds scary, however that is not the main reason
why it is a canonically bad idea to reuse DNS as a key distribution system.

The real problem is that DNS is designed operated and deployed as a name
infrastructure. The majority of the DNS servers are deployed without any
form of security analysis. Only a small number of TLDs have a comprehensive
security profile in place.

It is a very bad idea to make a change in a deployed protocol that changes
its status from a non-security infrastructure to a critical security
infrastructure.

From a technical point of view it is quite possible to integrate a Kerberos
style key distribution mechanism into DNS and if DNS was being designed from
scratch that is exactly what I would propose. However retrofitting any type
of primary key distribution scheme into a deployed service is completely
unacceptable.

There is a solution to this problem.

		DNS -> SRV -> XKMS

		Phill

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From: Ted Lemon <[email-masked]>
Date: Thu, 8 Aug 2002 13:53:45 -0500

> its status from a non-security infrastructure to a critical security

If this statement is true, then DNSSEC is a bad idea.   The whole point of 
DNSSEC is to be able to authenticate the answers that the name server gives.
    This is done using a secret key.   Compromise of that key allows the one 
who has compromised it to claim that invalid data is valid in a way that 
can be cryptographically authenticated.

So if you use DNSSEC, the DNS server *is* part of the critical security 
infrastructure.   There is no getting around this.   Once that genie is out 
of the bottle, it doesn't make any difference how many keys you store in 
the DNS, because you *have* to treat the DNS server as part of your 
critical security infrastructure.

BTW, please note that nobody is saying here that DNS should take the place 
of Kerberos or something like it.   Rather, what is being said is that 
there are applications where making a key available in the DNS makes sense.
    For example, an SSH host key can be used to verify that you are talking 
to the host associated with an A record that you've looked up.   This doesn'
t grant you access to the server - your private key does that.   What it 
does is to simply verify that you are talking to who you think you are 
talking to.   For this kind of security, storing keys in the DNS makes a 
lot of sense (to me, at least!).