LuhnCalc and bpay MOD10 version 5

Question

I am using the following PHP code to calculate a CRN for BPay:

<?php
function LuhnCalc($number) {
  $chars = array_reverse(str_split($number, 1));
  $odd = array_intersect_key($chars, array_fill_keys(range(1, count($chars), 2), null));
  $even = array_intersect_key($chars, array_fill_keys(range(0, count($chars), 2), null));
  $even = array_map(function($n) { return ($n >= 5)?2 * $n - 9:2 * $n; }, $even);
  $total = array_sum($odd) + array_sum($even);
  return ((floor($total / 10) + 1) * 10 - $total) % 10;
}
print LuhnCalc($_GET['num']);
?>

However it seems that BPAY is version 5 of MOD 10, for which I can't find any documentation. It seems to not be the same as MOD10.

The following numbers where tested:

2005,1597,3651,0584,9675

bPAY
2005 = 20052
1597 = 15976
3651 = 36514
0584 = 05840
9675 = 96752

MY CODE 
2005 = 20057 
1597 = 15974 
3651 = 36517 
0584 = 05843 
9675 = 96752

As you can see, none of them match the BPAY numbers.

Answer 1

This PHP function will generate BPay reference numbers based on the mod10 version 5 algorithm.

Who knows why BPay can't add this to their website. I only found an explanation by googling finding the algorithm being called "MOD10V05" instead of "Mod 10 version 5".

function generateBpayRef($number) {

    $number = preg_replace("/\D/", "", $number);

    // The seed number needs to be numeric
    if(!is_numeric($number)) return false;

    // Must be a positive number
    if($number <= 0) return false;

    // Get the length of the seed number
    $length = strlen($number);

    $total = 0;

    // For each character in seed number, sum the character multiplied by its one based array position (instead of normal PHP zero based numbering)
    for($i = 0; $i < $length; $i++) $total += $number{$i} * ($i + 1);

    // The check digit is the result of the sum total from above mod 10
    $checkdigit = fmod($total, 10);

    // Return the original seed plus the check digit
    return $number . $checkdigit;

}

Answer 2

Here's a way of implementing the "MOD10V5" algorithm (or "mod 10 version 5") using a t-sql user defined function in SQL server. It accepts a Customer ID up to 9 characters long, and return an 11 character CRN (Customer Reference Number).

I also prepended a version number onto the start of my CustomerID, you could do this too if you think you might end up changing it in the future.

CREATE Function [dbo].[CalculateBPayCRN]
(
    @CustomerID nvarchar(9)
)
RETURNS varchar(11)
AS
BEGIN

    DECLARE @NewCRN nvarchar(11)
    DECLARE @Multiplier TINYINT 
    DECLARE @Sum int
    DECLARE @SubTotal int  
    DECLARE @CheckDigit int  
    DECLARE @ReturnVal BIGINT

    SELECT @Multiplier = 1
    SELECT @SubTotal = 0

    -- If it's less than 9 characters, pad it with 0's, then prepend a '1'

    SELECT  @NewCRN = '1' + right('000000000'+ rtrim(@CustomerID), 9)

    -- loop through each digit in the @NewCRN, multiple it by the correct weighting and subtotal it:

    WHILE @Multiplier <= LEN(@NewCRN)  
    BEGIN  

        SET @Sum =  CAST(SUBSTRING(@NewCRN,@Multiplier,1) AS TINYINT) * @Multiplier  
        SET @SubTotal = @SubTotal + @Sum  
        SET @Multiplier = @Multiplier + 1  

    END 

    -- mod 10 the subtotal and the result is our check digit

    SET @CheckDigit = @SubTotal % 10  

    SELECT @ReturnVal = @NewCRN + cast(@CheckDigit as varchar)

    RETURN @ReturnVal
END
GO

Answer 3

Modula 10 V1 in PHP. Tested against my Windows dataflex routine and it is the same.

function generateBpayRef($number) {
    //Mod 10 v1
    $number = preg_replace("/\D/", "", $number);

    // The seed number needs to be numeric
    if(!is_numeric($number)) return false;
    // Must be a positive number
    if($number <= 0) return false;

    $stringMemberNo =  "$number";
    $stringMemberNo = str_pad($stringMemberNo, 6, "0", STR_PAD_LEFT);  
    //echo " Padded Number is $stringMemberNo  ";
    $crn = $stringMemberNo;

    for($i=0;$i<7;$i++){
           $crnval = substr($crn,(5-$i),1);
           $iPartVal = $iWeight * $crnval;

           if($iPartVal>9){
             //echo " Greater than 9: $iPartVal ";
             $firstChar = substr($iPartVal,0,1); 
             $secondChar = substr($iPartVal,1,1);                           
             $iPartVal=$firstChar+$secondChar;
             //$iPartVal -= 9;

           }
           $iSum+=$iPartVal;

           $iWeight++;
           if ($iWeight>2){$iWeight=1;}

           //echo " CRN: $crnval ] Weight: $iWeight ] Part: $iPartVal ] SUM: $iSum ";
    }
    $iSum %= 10;

    if($iSum==0){
        //echo " zero check  is $iSum ";                    
        //return $iSum;
    }
    else{
        //return 10-$iSum;
        $iSum=(10-$iSum);
    }
    //echo " Check is a $iSum ";                                        

    $BpayMemberNo  = $stringMemberNo . $iSum ;
    echo " New: $BpayMemberNo ";
    return ($BpayMemberNo);
}

Answer 4

Here is a ruby class I whipped up quickly for Mod 10 v5

module Bpay
  class CRN

    attr_accessor :number, :crn

    class << self

      def calculate_for(number)
        new(number).crn
      end

    end

    def initialize(number)
      @number = number
      calculate
    end

    def calculate
      raise ArgumentError, "The number '#{number}' is not valid" unless valid?

      digits      = number.to_s.scan(/\d/).map { |x| x.to_i }
      raise ArgumentError, "The number '#{number}' must be at least 2 digits in length" if digits.size < 2

      check_digit = digits.each_with_index.map { |d, i| d * (i + 1) }.inject(:+) % 10

      @crn = "#{number}#{check_digit}"
    end

    def valid?
      return false unless !!Integer(number.to_s) rescue false
      return false if number.to_i <= 0
      true
    end

  end
end

Answer 5

This is in C#, but this is what I have so far for BPay check digit generation:

private void btnBPayGenerate_Click(object sender, EventArgs e)
{
    var originalChars = txtBPayNumber.Text.ToCharArray();
    List<int> oddDigits = new List<int>();
    List<int> evenDigits = new List<int>();
    int oddTotal = 0, evenTotal = 0, total = 0, checkDigit ;

    const int oddMultiplier = 3;
    const int modulus = 10;
    bool isOdd = true;
    for (int x = 0; x < originalChars.Length; x++)
    {
        if(isOdd)
                oddDigits.Add(Int32.Parse(originalChars[x].ToString()));
            else
                evenDigits.Add(Int32.Parse(originalChars[x].ToString()));
            isOdd = !isOdd;
        }

        foreach (var digit in oddDigits)
            oddTotal += digit;

        foreach (var digit in evenDigits)
            evenTotal += digit;

        oddTotal = oddTotal * oddMultiplier;

        total = oddTotal + evenTotal;

        checkDigit = (modulus - (total % modulus));
lblBPayResult.Text = txtBPayNumber.Text + checkDigit.ToString();
}

I haven't completed testing this yet, I will post back once BPAY get back to me.

EDIT: try this: https://gist.github.com/1287893

Answer 6

I had to work out a version for javascript, this is what I came up with. It correctly generates the expected numbers in the original question.

var startingNumber = 2005;
var reference = startingNumber.toString();
var subTotal = 0;
for (var x = 0; x < reference.length; x++) {
    subTotal += (x + 1) * reference.charAt(x);
}
var digit = subTotal % 10;
var bpayReference = reference + digit.toString();

Answer 7

Here is a function I created using vb.net to calculate a mod 10 version 5 check digit

Private Function CalcCheckDigit(ByRef psBaseNumber As String) As String

    Dim lCheckDigit, iLoop As Integer
    Dim dCalcNumber As Double

    lCheckDigit = 0
    dCalcNumber = 0

    For iLoop = 0 To (psBaseNumber.Length - 1)

        lCheckDigit = lCheckDigit + (psBaseNumber.Substring(iLoop, 1) * (iLoop + 1))

    Next iLoop

    lCheckDigit = lCheckDigit Mod 10
    CalcCheckDigit = psBaseNumber & CStr(lCheckDigit)

End Function