Credit Card
On a credit card, a checksum is a single digit in the account number that allows a computer, or anyone familiar with the formula involved, to determine whether the number is valid. The checksum can help identify credit card numbers that have been entered incorrectly – or phony credit card numbers created by counterfeiters.
Foramt
The format of a credit card number is as follows:
First 6 digits: Issuer Identification Number (IIN)
Next 9 digits: Account Identification Number (AIN)
Last digit: Checksum
Luhn Algorithm
The Luhn algorithm is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers and other documents. Use of the Luhn algorithm is a way to speed up the verification process. The Luhn algorithm is particularly useful as more transactions are performed online, where data breaches can be made easily.