What Goes Into A Credit Card Number?

As we discussed earlier this week, while credit card numbers look random, they actually have an internal coding scheme. Here’s a further breakdown.

Credit cards numbers are instance of ISO 7812 numbers, developed by the International Organization for Standardization in 1989 to regulate all magnetic strip id cards.

Every credit card number consists of the following:

Single-digit Major Industry Identifier (MII)
• Six-digit issuer Identifier number (IIN)
• Account number
Single-digit checksum

Of note, the MII is considered part of the IIN. Also, an ISO 7812 number cannot be longer than 19 digits.

So, the next time you try to use your credit or debit card to enter an account number, be sure to leave off the first six digits and the last digit. — BEN POPKEN

ISO 7812 [Wikipedia]

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  1. pronell says:

    I never assume that a long number is random. Businesses like to do really stupid things, like using short random numbers, then run out and have to reuse them, and use really long strings of numbers with information encoded in them. And usually, of course, that’s information ABOUT YOU, and they don’t want you to know what they know ABOUT YOU. But they’re also so disorganized that if they just kept it in a file somewhere, they may not make the correlation later.

    Even the SSN contains information about where and when the number was issued, and it was only ever supposed to be used as a unique identifier for limited government programs.

  2. grant0 says:

    Actually, ISO stands for International Organization for Standardization, not International Standards Organization. It’s a “common misconception” says Wikipedia. See http://en.wikipedia.org/wiki/International_Organization_fo