"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