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.
FREE forever. Use the CDYNE Credit Card Verification Web Service or the
raw code used to program this Web Service.
Below you can find the C# or VB version of the Credit Card Verification
Web Service code using the Luhn Formula.
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.
using System;
///
/// Summary description for CCVerifier ///
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)
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
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);