2025-04-27

Why did all the numbers move to the back of my credit card?

One of my credit cards has a feature that baffles me: all the numbers are on the the same side1 of the card.

Now, credit cards present an interesting trade-off problem between security and convenience. Bruce Schneier spends some time on the matter in one of his books. Maybe Liars and Outliers. A certain level of loss to fraud is accepted to ensure that the system is convenient and ubiquitous; and the history of the technology is an epic tale of continual re-tuning of the risks.

In the very early days the system was surprisingly simply, relying on people and paper. Really. By the time I came on the scene, the cards had raised numbers on the front to impress multiple copies of the transaction record on carbon papers. The "chunk, chunk" of the cashier making the impression was the sound track of eighties retail. Later we got smart cards and now touchless payment.2

Hey, Ma! Look at me! I'm living in the future!

And somewhere along there (late '90s) the "card security code" was added to the back. It didn't show up on the mechanical impressions (still in use then in the US, if not in really advanced parts of the world) or in a single-sided xerox of the card, so it made it slightly harder for bad actors to capture enough information to create fraudulent charges. Not really hard, mind you. Just hard enough. That's one of the surprising things about this story.

But now I have this card that has the CSC printed right next to the main card number and expiration date.3 Huh? Is that Okay because merchants are now using billing zip code as an additional (if very weak) authenticator? Or is it something else?


1 The side with the magnetic strip and opposite the conductive pads which I would describe as the back, but it's the fact that they're all on the same side that bothers me.

2 The touchless systems marks one of the first moments I started to feel like technology was leaving me behind. Another unanticipated milestone.

3 It also has the main numbers printed flush on the surface of the card: they're not raised.

No comments:

Post a Comment