From: danisch@ira.uka.de (Hadmut Danisch)
Date: Mon, 18 Sep 95 09:58:44 PDT
To: cypherpunks@toad.com
Subject: Re: Explaining Zero Knowledge to your children
Message-ID: <9509181655.AA06115@elysion.iaks.ira.uka.de>
MIME-Version: 1.0
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> Clever, but I think it's missing an important element of zero knowledge
> interactive proof systems. For example, why not simply open _both_ hands?

That's the same problem as with the cave: Why not just go into the left
passage and come out of the right passage.


Both are absolute proofs. If you have two identical bills you must be able
to copy them.

In a cryptographical proof there is always the chance to guess. The chance
is sometimes 50%, sometimes very small.


What about this idea:

Alice is caught in a dark room somewhere on the world. She doesn't know
where she is, but there is a telephone in the room and she calls Bob to
ask him where she is. Bob claims to know it but doesn't want to reveal. 
He calls her back. When the phone is ringing, he has proven the knowledge
of her phone number, but she still doesn't know where she is or how he
could know. And there is still the chance that Bob has guessed the number.



Mmmh,

Hadmut