The Credit Card “Da Vinci Code”


This article was reported by Jay MacDonald for Credit

Did you know your credit card has a "Da Vinci Code"?

It’s true. Those raised numerals on your card are not only your account identifier that banks and merchants need to transact business on your behalf, but a little-known credit card version of the Da Vinci Code that verifies its validity without the aid of computers.

Even cooler, the code, which can reveal whether a credit card number is fraudulent, is cryptically hidden within the sequence of the card numbers. Every legitimate credit, debit and ATM card on Earth contains this formula.

What’s in your wallet, Dan Brown?  alt

This low-tech mathematical sleight of hand, dubbed the Luhn formula after its inventor, Hans Peter Luhn, played a tangential role in the development of the World Wide Web, search engines such as Google, text messaging and other high-tech wonders.

But there is absolutely nothing random about the final digit of your credit or debit card number. It has been appended as a so-called check number, or key, to verify the card is valid. It’s this check number that gives the Luhn formula its Da Vinci Code allure.

When a card number is generated using Luhn’s algorithm, various combinations of the digits on the card must ultimately add up to a number that is perfectly divisible by 10. For this reason, Luhn’s formula is also referred to as modulus 10, or mod 10 for short. Change any digit or transpose nearly any two digits, and the Luhn check will catch it.

The Luhn formula was designed to instantly detect accidental data entry errors — missed keystrokes, transpositions and the like — not as a defense against fraud. It doesn’t identify where an invalid number went sideways; it simply flags it as nonconforming.

Luhn checking won’t tell you anything about the underlying card account itself. Nor should it be confused with card-verification-value codes, those extra, unembossed numbers on major credit cards that attempt to verify that the physical card is (or has been) in your possession.

After joining IBM in 1941, Luhn pioneered fundamental concepts in business information retrieval, including keywords in context and selective dissemination of information. Those breakthroughs laid the groundwork for such ubiquitous computer processes as keyword search, e-mail, instant messaging and RSS feeds.

Although its original intent was to identify human error in the pre-computer days of manual data entry, the Luhn check remains a valuable first line of defense against credit card fraud today.

If the card numbers don’t tumble correctly through the algorithm (now computed literally faster than the blink of an eye), the transaction will be halted automatically before it even reaches the card issuer for authorization. Chances are excellent that the next line of anti-fraud software would net any fishy card numbers that slipped through the Luhn check.

If you want to see this in action check out this link and check your own cards.

For system concerns or problems, please call the CCS Retail Systems Support Department at 800-672-4806 or email_us

-Bryan alt


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