Luhn Algorithm
Luhn Algorithm is a Modulus 10 and Mod 10 , is a simple checksum formulae used for validating a variety of identification numbers, such as credit card numbers, IMEI numbers and Canadian Social Insurance Numbers.
How is the Formulae Work?
Let's supposed an example of a Debit / Credit Card number 4716 2495 3356 7731.
First, seperate card number into seperation of array, then followed by double every
second digit in the array.
| 4 | 7 | 1 | 6 | 2 | 4 | 9 | 5 | 3 | 3 | 5 | 6 | 7 | 7 | 3 | 0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 14 | 12 | 8 | 10 | 6 | 12 | 14 | 0 |
Secondly, If the doubled value ishigher than 9, seperate those numbers into array and get the sum of both.
| 4 | 7 | 1 | 6 | 2 | 4 | 9 | 5 | 3 | 3 | 5 | 6 | 7 | 7 | 3 | 0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 14 | 12 | 8 | 10 | 6 | 12 | 14 | |||||||||
| 5 | 3 | 1 | 3 | 5 |
Now Override those values before 9 , to existing card number,
4 + 7 + 1 + 6 + 2 + 8 + 9 + 5 + 3 + 6 + 5 + 6 + 7 + 7 + 3 + 0 = 79
\newline
\therefore This Card Is Not Valid:: Not A Multiple Of Ten