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Re: Name Constraints, was Re: [caops-wg] Re: ca signing policy file

Mike

this shows what a crap service Thawte are offering. Basically they will link any name to any public key, so the binding is worthless. YOu might as well issue your own self signed certificate.

As to your assertion that you have the same name on all your cards, well I would expect this, since all the cards belong to the same person.

Also I dont have a problem with two CAs issuing me with certs containing the same DN, in fact I would want them to. What I have an issue with is a CA issuing my name in someone else's cert. This shows that the CA is not authenticating the right to use the name.

BTW, the use of an email address is a perfectly good globally unique DN, and its pretty easy to prove ownership of it. This is how Verisign issue their certs. They send a secret to the mail box of the user.

regards

David


Mike Helm wrote:
Frank Siebenlist writes:
In other words, the Subject's DN should start with an identifier that essentially identifies the administrative domain in which the names are issued, e.g. \DOMAIN=ESNET.NET, followed by a \CN=abbf16d0-3b5f-11da-8cd6-0800200c9a66
In that way, a CA could be restraint to issue random names within a certain domain.

Here's the subject name I had from Thawte:
E = helm@fionn.es.net, CN = Michael Helm

That's it.

The E= was just for my convenience. I could create other certificates
with a different E= attribute if I needed to.

Name collisions by themselves - so what? I have the same
name on my driver's license and on my library card. Nobody
gets worked up over that. What I think you want, is
to make sure that same name string isn't certified to
two different people. But we don't have technical means
guarantee this. Even the current name constraints / signing policy
scheme cannot prevent this, it can only make it a little more
difficult.

You can eliminate most "legitimate" collisions by including
some link to the issuer in any authentication determination.
That's the administrative domain.

You find some CA issues duplicate DN's from other domains?
Don't use them. In any event, having an issuer field will limit what damage they can do.

You find some collision? You don't like it? Take it up with the CA's that
did it. They are highly motivated not to have this problem.

Why is this such a huge problem? I have never understood the amount of time & energy spent on it in our community. I sure wish we didn't have
the current signing policy file scheme.


--

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David W. Chadwick, BSc PhD
Professor of Information Systems Security
The Computing Laboratory, University of Kent, Canterbury, CT2 7NF
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Email: D.W.Chadwick@kent.ac.uk
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