The number printed in your credit card is not generated randomly. Credit cards numbers are based on a series of algorithms and combinations.

The numbers found on credit cards and bank cards have an internal structure, composed with:

• a single-digit Major Industry Identifier (MII),
• a six-digit Issuer Identification Number (IIN),
• an Account Number,
• a single Check Digit .

The first digit of your credit cards number is called the Major Industry Identifier (MII). This digit represents a category to which the entity that issued your credit card belongs to. Different MII digits represent different issuer categories, such as Airlines, Travel and entertainment, Banking and financial, etc.

For example, VISA and MasterCard belong to the banking and financial category.

The Issuer Identifier is represented by the first 6 digits of your credit cards number (including the initial MII digit). Different issuers have different identifier numbers, and this identifier number is unique for each issuer. This means that it is possible to have a maximum of a million issuers (10 raised to the sixth power = 1,000,000).

For example, the Issuer Identifier number of Visa and Master Card are:

• Visa: 4xxxxx
• Master Card: 51xxxx or 55xxxx

If the MII digit is 9, then the next three digits of the Issuer Identifier in your credit cards number are the 3-digit country codes defined in ISO 3166. The remaining two digits can be defined by the national standards of the specified country in whatever way it wishes.

Yourindividual account number is identified by digits 7 to (n - 1) of your credit cards number. The credit cards number does not have a fixed number of digits. However, its maximum length is 19 digits. The maximum length of the account number is12 digits.

The Check Digit is the final digit of your credit cards number. It is similar to a checksum. To arrive at the proper Check Digit it is used an algorithm called the Luhn algorithm, or Mod 10 check.

It was proposed in 1954, by Hans Luhn of IBM to be used as a validity criterion for a given set of numbers. Almost all credit card numbers are generated following this validity criterion.

As we have seen above, credit cards numbers are not generated randomly, but based on a series of algorithms and combinations.

In order to make a fake credit card number, a faker has to control the use of these algorithms. Many of them do not know this, and it is now easy even for you to see if many credit cards numbers are fake or not, reducing the prejudice it may cause you.

The Luhn algorithm is also used to verify if a given existing card number is valid or not.