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Validate credit card number with Mod 10 algorithm

, 15 Jan 2013 CPOL
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Article provides details about Mod 10 algorithm and how to validate a credit card number with mod 10 algorithm using C#.

Introduction

All you know what information contains in your NIC number. But do you know what information contains in the Credit Card Number? Following article provides brief details about what information contain in your credit card and demonstrates to how to validate credit card number using mod 10 (Luhn) algorithms with C#.

Background 

Card Length 

Typically, credit card numbers are all numeric and the length of the credit card number is between 12 digits to 19 digits. 

  • 14, 15, 16 digits – Diners Club
  • 15 digits – American Express
  • 13, 16 digits – Visa
  • 16 digits - MasterCard  

For more information please refer http://en.wikipedia.org/wiki/Bank_card_number.

Hidden information

  1.  Major Industry Identifier (MII) 
  2. The first digit of the credit card number is the Major Industry Identifier (MII). It designates the category of the entry which issued the card.    

    • 1 and 2 – Airlines 
    • 3 – Travel
    • 4 and 5 – Banking and Financial
    • 6 – Merchandising and Banking/Financial
    • 7 – Petroleum
    • 8 – Healthcare, Telecommunications
    • 9 – National Assignment 
  3. Issuer Identification Number 
  4. The first 6 digits are the Issuer Identification Number. It will identify the institution that issued the card. Following are some of the major IINs. 

  5. Amex – 34xxxx, 37xxxx 
  6. Visa – 4xxxxxx 
  7. MasterCard – 51xxxx – 55xxxx 
  8. Discover – 6011xx, 644xxx, 65xxxx 
  9. Account Number 
  10. Taking away the 6 identifier digits and the last digits, remaining digits are the person’s account number (7th and following excluding last digits) 

  11. Check digits   

Last digit is known as check digits or checksum. It is used to validate the credit card number using Luhn algorithm (Mod 10 algorithm). 

For more information refer: http://en.wikipedia.org/wiki/Bank_card_number and http://en.wikipedia.org/wiki/List_of_Issuer_Identification_Numbers.

Luhn algorithm (Mod 10)  

The Luhn algorithm or Luhn formula, also known as the “modulus 10″ or “mod 10″ algorithm, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in US and Canadian Social Insurance Numbers. It was created by IBM scientist Hans Peter Luhn. (http://en.wikipedia.org/wiki/Luhn_algorithm)

When you implementing eCommerce application, It is a best practice validating credit card number before send it to the bank validation.

Here are the Luhn steps which can used to validate the credit card number. 

4 0 1 2 8 8 8 8 8 8 8 8 1 8 8 1  

Step 1 - Starting with the check digit double the value of every other digit (right to left every 2nd digit)  

Step 2 - If doubling of a number results in a two digits number, add up the digits to get a single digit number. This will results in eight single digit numbers.

Step 2 

Step 3 - Now add the un-doubled digits to the odd places

 

Step 4 - Add up all the digits in this number

If the final sum is divisible by 10, then the credit card number is valid. If it is not divisible by 10, the number is invalid. 

Using the code   

Following code sample validates your credit card number against Mod 10. 

public static bool Mod10Check(string creditCardNumber)
{
    //// check whether input string is null or empty
    if (string.IsNullOrEmpty(creditCardNumber))
    {
        return false;
    }

    //// 1.	Starting with the check digit double the value of every other digit 
    //// 2.	If doubling of a number results in a two digits number, add up
    ///   the digits to get a single digit number. This will results in eight single digit numbers                    
    //// 3. Get the sum of the digits
    int sumOfDigits = creditCardNumber.Where((e) => e >= '0' && e <= '9')
                    .Reverse()
                    .Select((e, i) => ((int)e - 48) * (i % 2 == 0 ? 1 : 2))
                    .Sum((e) => e / 10 + e % 10);


    //// If the final sum is divisible by 10, then the credit card number
    //   is valid. If it is not divisible by 10, the number is invalid.            
    return sumOfDigits % 10 == 0;            
}

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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Tharaka MTR
Technical Lead Eyepax IT Consulting (Pvt) Ltd.
Sri Lanka Sri Lanka
Having more than 9 year hands-on industry experience in software development
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Comments and Discussions

 
QuestionWhy do you need to subtract each digit by 48? PinmemberRichard Hu12-Aug-14 22:13 
AnswerRe: Why do you need to subtract each digit by 48? PinprofessionalTharaka MTR13-Aug-14 9:34 
GeneralRe: Why do you need to subtract each digit by 48? PinmemberRichard Hu13-Aug-14 16:00 
GeneralMy vote of 5 PinmemberGrant Winney23-Jul-14 13:37 
GeneralRe: My vote of 5 PinprofessionalTharaka MTR23-Jul-14 22:52 
QuestionLamda Pinmembermajed samyal18-Sep-13 1:46 
AnswerRe: Lamda PinprofessionalTharaka MTR19-Sep-13 0:50 
QuestionDistinction Between Frequent Flyer and Credit Cards PinmemberPredrag Kos5-Jun-13 3:45 
QuestionMy vote 5 PinmemberYaseer Arafat1-Jun-13 12:46 
AnswerRe: My vote 5 PinprofessionalTharaka MTR2-Jun-13 3:15 
GeneralMy vote of 5 PinmemberRohan Leuva18-Apr-13 2:45 
GeneralRe: My vote of 5 PinmemberTharaka MTR18-Apr-13 2:50 
Generalthanks you very much Pinmemberbenjamin9x15-Apr-13 16:34 
GeneralRe: thanks you very much PinprofessionalTharaka MTR5-Jun-13 20:33 
QuestionAlternative method. PinmemberGeorge Swan17-Jan-13 8:55 
AnswerRe: Alternative method. PinmemberTharaka MTR17-Jan-13 9:56 

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