Luhn Algorithm Test: How the Mod 10 Check Works
Run a Luhn algorithm test by hand: double every second digit from the right, sum the digits, and pass the number when the total divides by 10.
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The Luhn algorithm is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers. This guide will walk you through the process of testing the Luhn algorithm.
The Luhn algorithm is based on the following steps:
Let's test the Luhn algorithm with a credit card number, for example, 4111111111111111.
Reverse the digits: 1, 1, 1, 1, 1, 1, 1, 1, 1, 4
Double every second digit from the rightmost side: 1, 2, 1, 2, 1, 2, 1, 2, 1, 8
Subtract 9 from the product: 1, 3, 1, 3, 1, 3, 1, 3, 1, 8
Add all the digits together: 1+3+1+3+1+3+1+3+1+8 = 32
The total modulo 10 is 2, which is not 0. Therefore, the credit card number is not valid according to the Luhn algorithm.
Testing the Luhn algorithm is a straightforward process that can help validate various identification numbers. By following the steps outlined in this guide, you can easily check the validity of numbers using the Luhn algorithm.