"Spoiling" digital cash

[jamesd at echeque.com]

    --
On 10 Dec 2001, at 16:16, georgemw at speakeasy.net wrote:

> An idea just popped into my head, I was wondering if anyone
> had thought of this before. Most likely someone has, and
> has either proven the idea is impossible or has figured out
> how to do it.
>
> Th idea is,  when buying some good or service with digital
> cash,  the customer first forwards the cash to the vendor 
> in some transformed way such that the vendor can't yet
> spend it, but can verify that it is good cash of the
> correct amount, and that the customer will no longer be
> able to spend it.
>
> The idea is, if the vendor follows through on his side, the
> customer will supply the additional information the vendor
> will need to redeem the cash.  The customer can still rip
> the vendor off by refusing to do so, but he has no
> incentive, the money's already gone for him.  Conversely, 
> an unscrupulous "vendor" could in principle trick a
> customer into throwing away money on nothing,  but he would
> gain no profit in doing so.

Vendor creates and blinds some tokens.  Asks buyer to have
them signed by money issuer.  Money issuer signs them, and
issues declaration that they have been signed.  Buyer gives
vendor the declaration, but not signatures.  After delivery,
gives signatures.


    --digsig
         James A. Donald
     6YeGpsZR+nOTh/cGwvITnSR3TdzclVpR0+pr3YYQdkG
     vNpp48iuJszNXUqQ3P9/e7GUOEcHXoIDo33hfuKd
     4xRG9QbdRJM31N1Lt+bhH55JK5VQWVorCJq0o7gAp