"Spoiling" digital cash

[David Honig]

At 09:48 PM 12/10/01 -0600, Jim Choate wrote:
>On Tue, 11 Dec 2001, Anonymous wrote:
>
>> To rip the coin, the passenger gives the taxi driver t = s^e1, along
>> with x.  The driver can verify that t^e2 = s^(e1*e2) = s^e1 = x mod n
>> which tells him that it is a real coin.  He also sends (t, x) to the
>> bank, which verifies that no such x has been spent before (no double
>> spending) and also stores x as a ripped coin such that only the driver
>> can spend it.
>
>Who pays for all this checking? Not only does this require the taxi driver
>to have a considerable store of computational and algorithmic 'equipment'
>but he's also got to have a comm channel to the bank.
>
>This don't sound cheap to execute at all...

Oh, you mean like the $5 charge that Mastercard/Visa charge merchants...

this *corroborates* the stuff Hettinga has been saying about it being
cheaper to use certain kinds of payment than others.