[Cryptography] French credit card has time-varying PIN

[Theodore Ts'o]

On Mon, Oct 03, 2016 at 11:44:03PM -0000, John Levine wrote:
> 
> It's the CVV, purely intended for card-not-present.
> 
> If the CVV changes every hour, and you allow one slot of slop for someone who
> places an order just before the number changes, that still makes it 500-1 to
> guess the right number, which seems pretty unfavorable for bad guys.

I suspect that even changing the CVV once a day (generated from the
hash of a secret plus the date) would be useful from an anti-fraud
perspective.

      	 	    		     - Ted