[E-Lang] Hash Chaining & Capabilities, Proposal #2d: Deputizing Remote Vats

[Bill Frantz]

At 02:42 PM 11/13/00 -0800, Nikita Borisov wrote:
>Bill Frantz writes:
>>(4) To protect from double spending, Bob must immediately clear the coin
>>with the bank, which is why the protocol is online.  Bob can be identified
>>if Alice and the bank cooperate.
>>
>>The offline protocol modifies the online protocol by:
>>
>>(0) Bob creates the coin, blinds it, and sends it to Alice.
>>
>>(1) Alice also blinds it with her own blinding factor.
>>
>>...
>
>I'm not sure that I would call this an offline protocol, since at step
>(2), Alice still has to interact with the bank.  It just shifts which of
>Alice and Bob talks to the bank.  The offline payment systems that I'm
>familiar with rely on auditable double spending; i.e. the protocol is
>payer anonymous if a coin has been spent only once, but the payer's
>identity is revealed in the case of double spending.

I think we have had a terminology shift from E to Digicash.  In E, we tend
to think of two-way communication as being online.  I think the Digicash
people think that if the response doesn't need to come quickly, it is
offline.  Online and offline are how they describe their protocols.

In either Digicash protocol, Alice has to get the bank to sign her coins,
which requires a round-trip communication.  However, this communication
does not have to happen quickly.  Mailing floppy disks would do.  The one
to watch is:

>(4) To protect from double spending, Bob must immediately clear the coin
>with the bank, which is why the protocol is online.  Bob can be identified
>if Alice and the bank cooperate.

In this case, Alice is waiting for whatever she is buying, and may not be
happy if she has to wait several days while Bob the validates the coin.