If a given retailer gets the same number off your card each time you do contactless, then that retailer /could/ track you via that number.
If all retailers get the same number, then they can each track you, and correlate your purchases between themselves.
Note, there just needs to be /some/ constant number from whatever comes through via contactless, the number does not have to be the magic numbers that post the sale to the card.
If all retailers get the same number, then they can each track you, and correlate your purchases between themselves.
Note, there just needs to be /some/ constant number from whatever comes through via contactless, the number does not have to be the magic numbers that post the sale to the card.