Hide a card number in a photo

A real test, not a pattern

A detector that flags any sixteen digits will flag order numbers, tracking codes and part numbers, and after the third false alarm people stop reading the results.

So the card detector runs the Luhn checksum, which every real card number satisfies and most random digit strings do not. What it reports is a number that could be a card, rather than a number that is the right length.

What else is on the card

The long number is the part people think about, and on its own it is usually not enough. The expiry date, the name and the security code on the back are what turn it into a usable set — and all three are in the same photograph.

Those are read as text as well, and sit under the other categories in the panel. Covering all of them takes one more click than covering the number alone.

The right way to send card details

Not in a photograph. If someone asks for a card number, read it to them, use the provider’s own sharing feature, or use a virtual card number you can cancel.

This exists for the photographs that already exist, and for the ones where the card is incidental — a receipt on a table, a card in the corner of a desk shot.

How to do it

1. 1Open the photoThe number is found and covered with a solid box.
2. 2Cover the name and expiry tooThey are listed separately, and they matter.
3. 3Save the copyThe pixels are replaced; the original stays with you.

Questions