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Delivered-To: clips@philodox.com
Date: Sat, 21 Jan 2006 09:12:05 -0500
To: "Philodox Clips List"
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Date: Fri, 20 Jan 2006 14:10:54 -0800 From: ericm@lne.com To: cypherpunks@jfet.org Subject: Re: Commercial Key Escrow? User-Agent: Mutt/1.4.1i Sender: owner-cypherpunks@jfet.org
On Fri, Jan 20, 2006 at 04:38:56PM -0500, R. A. Hettinga wrote:
At 1:26 PM -0800 1/20/06, ericm@lne.com wrote:
I'm looking for someone who provides an actual commercial key escrow service, not double encryption with a master key.
One would think that the effect, being the same, creates a distinction without a difference?
In some cases, yes. But not for this application.
I really am looking for a commercial trusted third party to hold keys.
I've found a bunch of references from ~10 years ago that say that someday commercial key escrow will be prevalent but it appears that someday hasn't yet arrived.
My problem is in many ways similar to the problem a CA would face in ensuring business continuity in a business that depends on keeping secrets.
What does say Verisign do to back up their root CA private keys? They probably have a bunch of BBN SafeKeypers (or rather the modern equivalent FIPS-140 hardware). What if all of them croak at the same time?
Do they keep multiple backups? What happens if the keys/passphrases for those backups are lost?
Or secret sharing? What if N-(K+1) shares are destroyed? Do they just quit the CA business then? There presumeably are scenerios under which that is the only answer, and Verisign has judged their possibility to be so remote and/or their solution cost so high that they are not worth defending against.
What would Verisign do if they didn't have security experts to decide what's an acceptable risk and what isn't, and instead just wanted to have someone else deal with the problem for them?
No matter what sort of architecture one chooses for long term key
protection it is inevitably going to fail once some threshold
fraction of the system fails. With a simply multiple copies system
you have to have 100% failure, but such a system has poorer security
properties. K-of-N threshold schemes fail once you've lost N-(K+1)
shares but generally have much better security. It is my
understanding that Verisign have multiple HSMs for the root and they
simply go out of their way to keep them very safe. At nCipher our
critical keys (such as firmware signing keys) are distributed using a
threshold scheme and we have procedures in place to periodically
check the integrity of each share (though never checking more than
one at a time).
As far as I know there are no active commercial key escrow services
around. One problem is that the half-life of Internet companies is
short compared to the time people seem to want to keep their keys so
it would be hard to trust such a company unless it was very carefully
set up.
Cheers,
Nicko
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R. A. Hettinga