LuhnCalc and bpay MOD10 version 5 - php

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