Subject: (ngtrans) RE: NGtrans - DNSext joint meeting, call for participation

From: "Christian Huitema" <[email-masked]>
Date: Wed, 25 Jul 2001 09:40:51 -0700

> Crawford wants your signatures today to last for a month. 
> What happens if you decide tomorrow to change a machine's 
> address list---for example, adding or removing a second address?
> 
> Answer: An attacker can interfere with this change for 29 
> agonizing days. All he has to do is replay the old data under 
> the old signature.

Dan,

What you are saying is that in order to deploy DNSSEC with confidence, a
domain administrator should be ready to resign all records on short
notice; you define short as one day, but we could easily imagine the
requirement being twice a day, as suggested in one of the IPv6
scenarios. There is some aesthetical beauty to the argument, but there
is also a flip side: it follows that domain administrators should not
deploy DNSSEC if they cannot resign everyone of their records in a
flash. So, the question is, how many iterations of Moore's law do we
have to wait for until this "renumbering in a flash" becomes reality?

Let's define flash as "a few minutes." If we believe Bill Sommerfeld
experiment with the mit.edu zone, we are not quite in flash territory
yet (90 minutes for 80,000 records), but we are not very far either.
Bill used a 333 MHz Celeron laptop; a dual processor 1.7 GHz server
could arguably do the job in about 10 minutes. If we changed nothing, if
the number of hosts per zone stayed roughly constant and if the key
length did not increased, then we could be in flash territory within two
iterations of Moore's law. This means that, for reasonable zones, the
impact of cost of signature on renumbering could disappear in about 3
years.

But Moore's law will not result in a straight gain. As the computers
become more powerful, we will need to increase the key length somewhat.
As the computers become less expensive, they tend to become more
numerous, and we may find more entries in any given zone. We may just as
well be 5 years away from nirvana. In between, DNSSEC deployment will
remain clumsy, and resigning will still be perceived as an expensive
operation.

I guess looking at the issue this way helps frame the debate: 3 to 5
years from now, there won't be much practical difference, from a cost of
signing point of view, between AAAA and A6. 

-- Christian Huitema