-----BEGIN PGP SIGNED MESSAGE----- Ok, I should start off by saying I'm not sure I followed everything Eric said in his post, so this might not be a great answer to him. My proposal isn't for an all inclusive, everything to all people, security system. It certainly would't preclude people from using other, stand alone systems, from using multiple sets of keys, or whatever else they wanted to do. My posts were predicated on the assumption that transparent encryption and signatures are worthwhile and necessary. By "traansparent encryption and signatures", I mean email systems that work and look pretty much like the programs we're using now -- elm and eudora, for example -- but which do crypto work automatically, behind the scenes. I think we ought to be moving in that direction, for two reasons. The first is that most people -- including most of us -- aren't willing to do much work in order to sign and encrypt our email traffic. If there's any penalty at all in terms of convenience, most people probably won't use a secure system. The second reason is that I believe it's only a matter of time until someone else institutes a transparent, reasonably secure email system. What would happen if Microsoft instituted a secure email system for their online customers, but took control over keys away from users? I think that the result would be that everyone would embrace the new system, because it would be a gigantic improvement over the status quo. We would compare the new system to an idealized vision, in which everyone has total control over their keys, who they trust, and in which law enforcement officials can't retrieve secret keys at will from some central repository. But everyone else would compare the new system to what we have now: an email system which is vulnerable to forging, and which isn't secure enough to transmit credit card numbers. I think that if we can't field an alternative, usable system, something that's practical and easy to use, we're going to lose by default. I'm not under any delusion that what I've proposed is some kind of magic answer. I'm not a heavy hitter, in a technical sense, like Eric, Hal, Tim, and many of the others here are. But at the same time, I think there's some need for compromise. We need a transparent system that can embrace people who aren't willing to put a lot of effort into security, but at the same time is able to accomodate people who want to take more trouble for the sake of their privacy.

This whole area of key distribution has generated much confusion. A perfect world is described, and then everyone is assumed to participate in achieving this world. This approach of generality, however, is notably more complicated than a world where responsibility for security is partitioned, where each user does not have to worry about all the possible systemic security issues.

I understand this criticism. But if we abandon generality, I don't think we can achieve transparency. And as I said before, I think a transparent system is going to come out on top. It's true that what I proposed is complicated, but a lot of the net is pretty complicated when you take off the lid. I think it could still be made usable.

Proposition: You don't need to be responsible for making sure that the other person is being spoofed; that's their responsibility.

A common situation where this proposition makes a significantly simpler system is exactly in the case described, where you and your email correspondents wish to exchange keys. Suppose, in addition, that you two met online and that your only channels of communication are electronic. The goal here is to create persistence of identity; identification with a physical body is not needed.

Actually, I wasn't trying to identify keys with physical bodies, but rather with email addresses. But the whole point of the system is that there is no need for the two correspondents to worry about exchanging keys: it all happens automatically. People who are doing unusual things, like creating nyms, would of course be free to take unusual actions.

In the PGP case you start with your own key, which you trust, then look for a chain of signatures to the destination. This chain can be rather cumbersome to produce. It's overkill, as well, since all you really needed to know is that the key was not being translated on your own end. The PGP trust chain largely accomplishes that, true, but not as simply as possible.

I'm not sure I follow the last part of this.

Alternatively, you save the first piece of email that you receive from your correspondent; it has a digital signature on it. Now _by whatever means_, you obtain a public key by which to verify that signatures on email you receive are the same. You yourself need to ensure that you aren't getting spoofed; you can do this by, say, having your correspondent send mail to two different locations, or by using a second channel to obtain the key by, or by using a PGP trust chain, if one is available.

Again, I go back to my goal (which wasn't stated clearly enough in my original posts, to be sure) of transparency, and of trying to get the bulk of day to day email encrypted.

The original model for public key communications seems to have been one channel with an interposer. The real world is much more complicated than that. One can obtain good protection, at least as good as a trust chain, by crossing organizational boundaries. The argument that trust chains are better because they are cryptographic carries no weight; the decision at each link to make a signature is of social, not cryptographic, character.

I agree with this 100%. This is part of what I was trying to accomodate. On the low end, we have a default web of trust, which is sort of crummy because it's not terribly difficult to spoof. Cryptographically, it's very sound, but socially, it's quite weak. But my goal was to meet this criticism by making the system open to other webs, and to place as few restrictions as possible on people who want to create and use alternative webs. Those alternative webs could tie email addresses and keys to physical persons, or to nyms, or to anything else they wanted. They could be as rigid or as lax as they pleased. And we as users could decide which webs we were willing to trust.

In particular, the design of PGP that ties key management inextricably to encryption is bad and will contribute to an inflexibility that will eventually sink PGP if it is not corrected.

Could you elaborate on this?

Perhaps we would have a default web, which would have everyone's key in it.

This is a really bad idea. Some "public" keys should not be made public, but rather revealed only to the correspondent. Forward secrecy is the reason. If the public key has never been in the possession of an opponent, and assuming the results of the public key operation yield little or no information about the modulus, then when the keys are changed and destroyed, no amount of factoring can find the private key because the public key isn't around to factor.

You could still do this. I did not phrase this well, and I can see where your concern comes from. I have a few nyms, and I don't publish all of my public keys. I didn't mean to imply that all public keys ought to be on the default web. I meant that you ought to be able to get *a* public key for an aribitrary address from the default web. I have used a couple of nyms over the past couple of years, and I haven't published those public keys or tried to associate them with my email adddresses. That would be, as you pointed out, a bad idea. But at the same time, I have a public key for my address here, alex@omaha.com, that I want to publish as widely as possible. Right now, it's available via finger at astrashe@nyx.cs.du.edu. The system I proposed is just an elaborate (probably too elaborate) substitution for getting the key via finger, with the intention of making transparent secure mail possible. Basically, it comes down to this: in a transparent system, if you want to mail me, somehow your mailer will have to get a copy of my key without your doing anything about it. More importantly, your mailer will have to decide if it should trust the key it retrieves without asking you. Otherwise, it wouldn't be transparent. The problem is: how do we let the machine make this decision on it's own, without imposing a single web of trust on users? That's what I'm trying to get at.

Eric

Thanks for the thoughtful response, I appreciate it. == Alex Strasheim | finger astrashe@nyx.cs.du.edu alex@omaha.com | for my PGP 2.6.1. public key -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBLtpn7xEpP7+baaPtAQHoIgP/SmOcR2a8PXEwHdF5ROfTmQ2GVxg0ZhlY LYvUKFB+phV7RZAjlP3OCpEjchxTpzaiJFgM4+wtKulrD0ZdGfyF6iGM+K8OTAql lWMfJ25/AvfTlqfBlZ0TAX4hkEWF5r3D65TpncgR7VOF8XErmFPPEvVCvZhx6Rd/ koZmgdTIoXg= =vJqj -----END PGP SIGNATURE-----