Re: Anonymous Auth Certificates [was: Re: Blinded Identities]
From: Carl Ellison <cme@acm.org>
Steve Shear <azur@netcom.com> writes:
[much cut]
I've been charged with developing an Internet service which needs to assure its clients of anonymity. However, we fear some clients may abuse the service and we wish to prevent the abusers from re-enrollment if terminated for misbehavior. (In your example, it would be the person(s) trying to discover the service host via flood).
My thought was to base enrollment on some sort of 'blinding' of their certified signature (e.g., from Verisign) which produces a unique result for each signature but prevents the service from reconstructing the signature itself (and thereby reveal the client's identity). I'm calling this negative authentication.
The mistake is to think of using ID certificates (like those from Verisign) in the first place. They don't mean anything.
You want an authorization certificate, such as produced by SPKI. You need to know what a key is authorized to do, not what name is associated with the key.
(Sorry about quoting so much, but I liked Steve Shear's succinct problem statement.) I don't see how authorization certificates solve this problem. How would you determine if someone was qualified to receive an authorization certificate? And what would you do to make them stop using the service if they abuse it, and to stop them from getting new authorization certificates? Thanks, Hal
At 18:33 -0400 10/17/96, Hal Finney wrote:
I've been charged with developing an Internet service which needs to assure its clients of anonymity. However, we fear some clients may abuse the service and we wish to prevent the abusers from re-enrollment if terminated for misbehavior. (In your example, it would be the person(s) trying to discover the service host via flood).
I don't see how authorization certificates solve this problem. How would you determine if someone was qualified to receive an authorization certificate? And what would you do to make them stop using the service if they abuse it, and to stop them from getting new authorization certificates?
You're right. SPKI doesn't solve the whole problem, by itself. You do need to avoid ID certificates in the first place. They have no use here because he wants anonymous authorization. He also wants it blinded. SPKI includes a construct for passing some authorization to anything signed by a given public key. That gives him his blinding. However, he has an additional problem. He's trying to set up what amounts to a voter registration. Rather, he appears to hope that someone else will do so. AFAIK, there is no currently proposed PKI which will do the (one body:one valid cert) mapping he's looking for. However, if he finds some organization willing to do that, then he can use the SPKI certs to transfer authorization (e.g., to log in on his service) to a key used for that purpose by that organization. Certainly, ID certs from VeriSign or GTE or anyone else I've heard of don't fill that role. As a native Chicagoan, I can attest to the difficulty of performing (one body):(one vote) mappings :) [I know -=- slander of my beloved home town] I'm also not sure we want anyone setting up such a service except for voting. There can be very bad societal drawbacks to a service like that. It might be able to achieve all the evil which we decry when the idea of a national ID card comes up. - Carl +------------------------------------------------------------------------+ |Carl M. Ellison cme@acm.org http://www.clark.net/pub/cme | |PGP: E0414C79B5AF36750217BC1A57386478 & 61E2DE7FCB9D7984E9C8048BA63221A2| | "Officer, officer, arrest that man! He's whistling a dirty song." | +-------------------------------------------- Jean Ellison (aka Mother) -+
participants (2)
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Carl Ellison -
Hal Finney