Credit Card Verification

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Verify a Credit Card for free by cross referencing it against the Luhn formula. This formula does not check with the major Credit Card companies for validity, it merely checks the Credit Card number algorithm to make sure it is a valid number for the four major Credit Cards accepted worldwide. Please use a license key of '0' if consuming via Web Service. The Luhn formula can also be used to identify the type of card by the # entered.

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FREE forever. Use the CDYNE Credit Card Verification Web Service or the raw code used to program this Web Service.

Download Credit Card Verification Web Service code examples

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Below you can find the C# or VB version of the Credit Card Verification Web Service code using the Luhn Formula.

Luhn Definition

The Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm, was developed in the 1960s as a method of validating identification numbers. It is a simple checksum formula used to validate a variety of account numbers, such as credit card numbers and Canadian Social Insurance Numbers. Much of its notoriety comes from credit card companies' adoption of it shortly after its creation in the late 1960s by IBM scientist Hans Peter Luhn (1896–1964).

Explanation of the Luhn's algorithm can be found here.

C# Source Code

using System;
 
/// <summary>
/// Summary description for CCVerifier
/// </summary>
public class CCVerifier
{
 
public ReturnIndicator CheckCC(string CardNumber)
{
ReturnIndicator ri = new ReturnIndicator();
ri.CardValid = false;
 
 
byte[] number = new byte[16]; // number to validate
 
// Remove non-digits
int len = 0;
for (int i = 0; i < CardNumber.Length; i++)
{
if (char.IsDigit(CardNumber, i))
{
if (len == 16) return ri; // number has too many digits
number[len++] = byte.Parse(CardNumber[i].ToString());
}
}
 
// Use Luhn Algorithm to validate
int sum = 0;
for (int i = len - 1; i >= 0; i--)
{
if (i % 2 == len % 2)
{
int n = number[i] * 2;
sum += (n / 10) + (n % 10);
}
else
sum += number[i];
}
 
ri.CardValid = (bool) (sum % 10 == 0);
if ((ri.CardValid == true))
{
switch (CardNumber.Substring(0, 1))
{
case "3":
ri.CardType = "AMEX/Diners Club/JCB";
break;
case "4":
ri.CardType = "VISA";
break;
case "5":
ri.CardType = "MasterCard";
break;
case "6":
ri.CardType = "Discover";
break;
default:
ri.CardType = "Unknown";
break;
}
}
else
{
ri.CardType = "NONE";
}
return ri;
}
 
 
public class ReturnIndicator
{
public string CardType;
public bool CardValid;
}
}

The original code below (at the bottom) is INCORRECT... this one is used and tested and reflects the C# above more


Dim theNumber As String = Misc.Strings.MakeAllNumeric(accountNumber) 'i.e. 1234-5678-9012-3452 = 1234567890123452 If String.IsNullOrEmpty(theNumber) Then Return False

'Process digits from right to left Dim sum As Int32 = 0 Dim theDigit As Int32 = 0 For i As Int32 = theNumber.Length - 1 To 0 Step -1

  theDigit = Convert.ToInt32(theNumber.Substring(i, 1)) 'GET THE DIGIT (starting from the right)
  'USE THE EVEN DIGIT on EVEN LEN CARDS; ODD DIGIT on ODD LENGTH CARDS
  'EXAMPLE: "even" len card number ending in xxx51908
  '           8 + (0*2) + 9 + (1*2)          
  'EXAMPLE: "odd" len card number 49927398716
  '           6 + (1*2) + 7 + (8*2) + 9 + (3*2)... you get the point... but see next line
  '           6 + 2     + 7 + (1+6) + 9 + 6.... see the "break apart" the 16 = 1 + 6
  If ((i Mod 2) = (theNumber.Length Mod 2)) Then
     'the product = (theDigit * 2)
     'example: 6*2 = 12 or 9*2 = 18 or 7*2 = 14
     ' OVER 9 THEN Break the digits up and add them together (eg. 18 becomes 1 + 8, 14 becomes 1 + 4)
     ' UNDER 10 THEN JUST ADD IT
     If (theDigit * 2) >= 10 Then
        sum += ((theDigit * 2) \ 10) + ((theDigit * 2) - 10)
     Else
        sum += (theDigit * 2)
     End If
  Else
     sum += theDigit
  End If

Next

'RETURN 10's COMPLIMENT Return ((sum Mod 10) = 0)


              • ORGINAL CODE ******

VB.Net Source Code

Public Class CreditCardLib
Public Enum eCreditCardType
Invalid = 0
AMEX = 3
Visa = 4
MasterCard = 5
Discover = 6
End Enum
 
Public Shared Function CheckCardNumber(ByVal CardNumber As String) As eCreditCardType
Dim SingleChar As String
Dim CharValue As Integer
Dim RunningValue As Integer = 0
Dim Result As eCreditCardType
 
CardNumber = Replace(Replace(Replace(CStr(CardNumber), "-", String.Empty), " ", String.Empty), ".", String.Empty) 'Help ensure proper format of the input
Dim NumberLen As Integer = Len(CardNumber)
 
' Default value
Result = eCreditCardType.Invalid
Select Case Left(CardNumber, 1)
Case "3"
'AMEX: 15 digit numbers starting with 34 or 37
If NumberLen = 15 And (Left(CardNumber, 2) = "34" Or Left(CardNumber, 2) = "37") Then
Result = eCreditCardType.AMEX
End If
Case "4"
'Visa: 13 or 16 digit numbers starting with 4
If NumberLen = 13 Or NumberLen = 16 Then
Result = eCreditCardType.Visa
End If
Case "5"
'MasterCard: 16 digit numbers starting with 5
If NumberLen = 16 Then
Result = eCreditCardType.MasterCard
End If
Case "6"
'Discover: 16 digit numbers starting with 6011 or 65
If NumberLen = 16 And (Left(CardNumber, 4) = "6011" Or Left(CardNumber, 2) = "65") Then
Result = eCreditCardType.Discover
End If
End Select
 
If Result <> eCreditCardType.Invalid Then
'Process digits from right to left, drop last digit if total length is even
Dim w As Integer = 2 * (NumberLen Mod 2)
For i As Integer = NumberLen - 1 To 1 Step -1
SingleChar = Mid(CardNumber, i, 1)
If IsNumeric(SingleChar) Then
Select Case (i Mod 2) + w
Case 0, 3 'Even Digit - Odd where total length is odd (eg. Visa vs. Amx)
RunningValue += CInt(SingleChar)
Case 1, 2 'Odd Digit - Even where total length is odd (eg. Visa vs. Amx)
CharValue = CInt(SingleChar) * 2
If CharValue > 9 Then
'Break the digits (eg. 19 becomes 1 + 9)
RunningValue += (CharValue \ 10) + (CharValue - 10)
Else
RunningValue += CharValue
End If
End Select
End If
Next
 
'Return the 10's complement of the total
RunningValue = 10 - (RunningValue Mod 10)
If RunningValue > 9 Then
RunningValue = 0
End If
 
' Finally, check the checksum digit. If it's invalid then we have an invalid card.
If (CStr(RunningValue) <> Right(CardNumber, 1)) Then
Result = eCreditCardType.Invalid
End If
End If
 
Return Result
End Function
End Class

PHP Example for Web Service

 
 
class CCVerify {
	private $CardNumber;
	public $response;
 
 	public function __construct($CardNumber) {
		$this->CardNumber = $CardNumber;
		$this->getResponse();
	}
	public function getResponse(){
		$url = "https://ws.cdyne.com/creditcardverify/luhnchecker.asmx";
		$url .= "/CheckCC?CardNumber=" . $this->CardNumber;
		$this->response = simplexml_load_file($url) or die("ERROR");
	}
 }
 $CardNumber = "123412341243124";
 $results = new CCVerify( $CardNumber );
 var_dump($results);
 
 
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