From: Carl Ellison <cme@ACM.ORG>
Date: Thu, 17 Oct 1996 10:06:07 -0700 (PDT)
To: Steve Schear <azur@netcom.com>
Subject: Anonymous Auth Certificates [was: Re: Blinded Identities]
In-Reply-To: <v02130503ae865897f409@[10.0.2.15]>
Message-ID: <v03007802ae8c171fb5bc@[168.143.8.144]>
MIME-Version: 1.0
Content-Type: text/plain


At 16:28 -0400 10/13/96, Michael Froomkin - U.Miami School of Law wrote:
>[cc'd to coderpunks]
>
>On Sun, 13 Oct 1996, Steve Schear wrote:
>
>> >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.
>>
>> Have you come across anyone who has considered this problem or
>> another one which is mathematically very similar?

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.

Check out

http://www.clark.net/pub/cme/spki.txt
and
http://theory.lcs.mit.edu/~rivest/publications.html in the SDSI section.

 - Carl


+------------------------------------------------------------------------+
|Carl M. Ellison   cme@acm.org     http://www.clark.net/pub/cme          |
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|  "Officer, officer, arrest that man!  He's whistling a dirty song."    |
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