[13025] in Cypherpunks
Re: Why Digital Cash is Not Being Used
daemon@ATHENA.MIT.EDU (Perry E. Metzger)
Wed May 4 12:48:39 1994
To: "Michael V. Caprio Jr." <mikecap@wpi.edu>
Cc: cypherpunks@toad.com
In-Reply-To: Your message of "Wed, 04 May 1994 12:20:39 EDT."
<199405041620.MAA04197@coyote.WPI.EDU>
Reply-To: perry@imsi.com
Date: Wed, 04 May 1994 12:35:52 -0400
From: "Perry E. Metzger" <perry@snark.imsi.com>
"Michael V. Caprio Jr." says:
>
> > 2) In order to demonstrate that you have it you generally speaking
> > have to have already given it away.
>
> I would use the analogy of information as shares... It also seems
> that number two is a typical zero knowledge situation -
No its not. Its easy to conduct a zero knowledge interactive theorem
proof for things that are mathematically expressable, like "I know a
Hamiltonial circuit of this graph", but it won't work for anything
that can't be expressed that way.
Example: construct a zero knowledge proof for the proposition "I know
something interesting about George Bush that you would be willing to
pay $100 to know".
> BTW, what is fungible?
A fungible thing, sometimes called "a commodity", is one for which the
all are oblivious to substitution. As an example, when you request a
dollar bill from me, you don't care WHICH dollar bill you get. When
you ask for a one kilo gold ingot, which ingot from the space of all
ingots doesn't matter to you.
Only fungibles can be traded in securities markets or deposited in
accounts. I can trade shares of IBM because you have no care which 100
shares of IBM you get. I can trade futures contracts for West Texas
Intermediate Crude because thats a very well specified substance.
Currency is ALWAYS fungible. That which is not fungible cannot be used
as a currency. In particular, "information" is not fungible. It is not
a commodity. Two pieces of information are not indistinguishable.
Perry
