Re: CC fingerprints

[Adam Shostack <adam@homeport.org>]

harka@nycmetro.com wrote:

| Their solution, called the Magneprint system, reads the millions of tiny
| magnetic particles, which are unique on each card, says Professor Ronald
| Indeck.
| Each magnetic stripe on the card has two important areas. The first looks
| like a bar code, which contains the account number. The rest is a random
| pattern of magnetic information -- a signature that is different on every
| card and impossible to duplicate, Indeck says.

	"Impossible to duplicate."  Perhaps he has never heard of the
ironing trick?  (You use an iron to heat one card in the proximity of
the other.  This breaks up the cohesion of the particles on the card
close to the iron.  The magnetic field in the other card causes the
particles to realign themselves as they cool.)

	I suspect that a conventional card reader won't duplicate the
other areas of the card.  But the duplicability of bits is a
fundamental fact. Thats why Chaum's original systems are online, and
safer than the smartcard system.  The smartcard based systems depend
on the cost of breaking behing higher than the payoff for criminals.
(Or the cost of breaking the smartcard based system as opposed to
breaking some other system.)

	A mag stripe card, with no defenses built in, can be
duplicated.  Are they offering prize money for beating thier system?
My only worry would be that they read finely enough that they notice
small deviations in the duplicate.

Adam


-- 
"It is seldom that liberty of any kind is lost all at once."
					               -Hume