Re: Digital cash & multiple spending.

[GRABOW_GEOFFREY@tandem.com]

    I work with many institutions that use or create POS systems.
Some of them have gone to using tamper resistant smart cards that
debit themselves and "can't be modified by a user.".  The card has
some keys and some crypto stuff in 'em that only allows authorized
locations (those with the keys) to credit the balance on the card.
It's my understanding that the cards cost around $7 and with care
have a MTBF of 18-24 months.
Additionally, these systems, which are offline, execute batch jobs
at night to compare the spent monies with the balance in the bank's
database.  If anyone has gone over their limit, the card is flagged
and a "HOT" card file is downloaded to the POS locations.  The POS
device will not allow "HOT" cards to be used.  This limits multiple
spending to a 24 hour period.
                                                     G.C.G.

 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 | Geoffrey C. Grabow          | "What we demand are rigidly defined    |
 | Oyster Bay, New York        |   areas of doubt and uncertainty!"     |
 |                             |         --------------------           |
 | grabow_geoffrey@tandem.com  | Clipper, SkipJack & Digital Telephony  |
 |                             |             JUST SAY NO!!!             |
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