function extra_l33t_entropy($match)
{
if (!isset($match['l33t'])) {
return 0;
}
$possibilities = 0;
$sub = $match['sub'];
foreach ($sub as $subbed => $unsubbed) {
$S = 0;
$U = 0;
foreach (str_split($match['token']) as $chr) {
if ($chr === (string) $subbed) {
$S += 1;
} elseif ($chr === $unsubbed) {
$U += 1;
}
}
$len = min($U, $S);
for ($i = 0; $i <= $len; $i++) {
$possibilities += binomial_coefficient($U + $S, $i);
}
}
# corner: return 1 bit for single-letter subs,
# like 4pple -> apple, instead of 0.
$entropy = logarithm($possibilities);
return $entropy ? $entropy : 1;
}
<?php
$logs = array(2 => 103, 3 => 163, 5 => 239, 7 => 289, 11 => 356, 13 => 381, 17 => 421, 19 => 437.5);
for ($number = 1; $number <= 256; $number++) {
echo $number;
echo ' ';
//var_dump(factorise($number));
echo logarithm(factorise($number));
echo '<br>';
}
function factorise($number)
{
$factors = array();
$root = floor(sqrt($number));
for ($divisor = 1; $divisor <= $root; $divisor += 2) {
$factor = $divisor == 1 ? 2 : $divisor;
if ($number % $factor == 0) {
$number = $number / $factor;
$factors[] = $factor;
$divisor = -1;
}
}
if ($number > 1) {
$factors[] = $number;
}
return $factors;
}
function logarithm($factors)
{
global $logs;
$sum = 0;
