In response to some things I said about crypto and firewalls, Adam Back wrote:
I'm not sure whether pgp5.5 has this ability to screen messages prior to reading, and also not sure whether it has the ability to snoop messages prior to sending built in.
It's not a feature of 5.5, it's a separate activity that relies on the presence of a third party key. The actual inspection occurs at a security choke point like a firewall. That way the tests are applied consistently regardless of mistakes made by clients in software installation or configuration. You noted that it might in fact be possible to get the same result with a more GAK resistant implementation, and I agree. For example, if the principals all update their public keys fairly often, then there's no relatively key that's easy to escrow. The practical version of forward secrecy, as it were. I have no objection to that. As far as I can tell, there's nothing intrinsic in the current PGP proposals to prevent such an implementation. Concerning your other examples, I agree that there are ways to trade off between degrees of GAK sensitivity and various customer security objectives. However, this whole discussion revolves around the fact that people rely heavily on off the shelf solutions, and there aren't the right tools to do everything you're suggesting. I'd like to see things in the crypto marketplace be as flexible as possible. Just because a few provide some features that could in theory be applied to GAK doesn't IMHO mean that those will manage to prevail. A diverse marketplace of crypto devices is essential for it to flourish -- one that gives every customer the flavor they want. That way the general public will develop a working understanding of it. And we'll all learn what really works and what doesn't. Let's face it, crypto is at about the same stage as cars were when Henry Ford started building them. We really know as much about how crypto will change the future as he did about the effects of cars. We can't start engineering in governors to restrict our speed, or be restricting our designs to governor-proof transmissions. I regret I'll have to bow out of this discussion because I'll be on travel for a couple of weeks. Have fun everyone. Rick. smith@securecomputing.com Secure Computing Corporation "Internet Cryptography" now in bookstores http://www.visi.com/crypto/