How to validate a Singaporean FIN?

Question

Can anyone provide an algorithm to validate a Singaporean FIN?

I know with a Singaporean NRIC I can validate it via modulo 11 and then compare the result to a lookup table but cannot find a similar lookup table for the FIN.

I also do not know for sure if the modulo 11 is the correct method to validate.

I am aware the government sells a algorithm for $400 but maybe someone knows a cheaper way.

Bonus points for c# implementation.

Answer 1

And again in PHP

function isNricValid ($theNric) {

    $multiples = array( 2, 7, 6, 5, 4, 3, 2 );

    if (!$theNric || $theNric == '')
    {
        return false;
    }

    if (strlen($theNric) != 9)
    {
        return false;
    }

    $total = 0;
    $count = 0;
    $numericNric = 0;

    $first = $theNric[0];
    $last = $theNric[strlen($theNric) - 1];

    if ($first != 'S' && $first != 'T')
    {
        return false;
    }

    $numericNric = substr($theNric, 1, strlen($theNric) - 2);

    if (!is_numeric ($numericNric)) {
        return false;
    }

    while ($numericNric != 0)
    {
        $total += ($numericNric % 10) * $multiples[sizeof($multiples) - (1 + $count++)];

        $numericNric /= 10;
        $numericNric = floor($numericNric);
    }

    $outputs = '';
    if (strcmp($first, "S") == 0)
    {
        $outputs = array( 'J', 'Z', 'I', 'H', 'G', 'F', 'E', 'D', 'C', 'B', 'A' );
    }
    else
    {   
        $outputs = array( 'G', 'F', 'E', 'D', 'C', 'B', 'A', 'J', 'Z', 'I', 'H' );
    }

    return $last == $outputs[$total % 11];

}

function isFinValid ($fin)
{
    $multiples = array( 2, 7, 6, 5, 4, 3, 2 );
    if (!$fin || $fin == '')
    {
        return false;
    }

    if (strlen($fin) != 9)
    {
        return false;
    }

    $total = 0;
    $count = 0;
    $numericNric = 0;
    $first = $fin[0];
    $last = $fin[strlen($fin) - 1];

    if ($first != 'F' && $first != 'G')
    {
        return false;
    }

    $numericNric = substr($fin, 1, strlen($fin) - 2);

    if (!is_numeric ($numericNric)) {
        return false;
    }

    while ($numericNric != 0)
    {
        $total += ($numericNric % 10) * $multiples[sizeof($multiples) - (1 + $count++)];

        $numericNric /= 10;
        $numericNric = floor($numericNric);
    }

    $outputs = array();

    if (strcmp($first, 'F') == 0)
    {
        $outputs = array( 'X', 'W', 'U', 'T', 'R', 'Q', 'P', 'N', 'M', 'L', 'K' );
    }
    else
    {
        $outputs = array( 'R', 'Q', 'P', 'N', 'M', 'L', 'K', 'X', 'W', 'U', 'T' );
    }

    return $last == $outputs[$total % 11];
}