From: Adam Back <aba@dcs.ex.ac.uk>
Date: Sun, 17 Nov 1996 14:51:35 -0800 (PST)
To: ses@tipper.oit.unc.edu
Subject: Re: Members of Parliament Problem
In-Reply-To: <Pine.SUN.3.91.961117133019.11544A-100000@tipper.oit.unc.edu>
Message-ID: <199611171837.SAA00457@server.test.net>
MIME-Version: 1.0
Content-Type: text/plain



Simon Spero <ses@tipper.oit.unc.edu> writes:
> On Fri, 15 Nov 1996, Rich Graves wrote:
> 
> > Peter Hendrickson wrote:
> > > 
> > > 
> > > There are times when one wishes to speak anonymously, yet speak
> > > as a member of a group.
> > 
> > You either need to trust a shared server to know and then blind your 
> > identity, or trust the people with whom you share a secret key not to 
> > give that key to non-group members.
> 
> Why not use  blinding for obtaining the certificate? 
> 
> Create a number up public/private key pairs, blind them, then do the
> cut-and-choose thing with the security officer. He signs the blinded key,
> then returns it. Unblind the remaining pubic key, and you've got a public
> key with the appropriate signature on it. 

Reasonable, except that it's linkable.  You may not want it to be
linkable, because the more messages signed with the key, the greater
the chance that speech paterns give away the speaker.

Adam
--
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)]}\EsMsKsN0[lN*1lK[d2%Sa2/d0<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<J]dsJxp"|dc`