Me ha quedado de esta forma:
Código PHP:
function EncryptDecrypt($str, $mode = "E") {
$UserKey = "IRONMAN";
$n = strlen($UserKey);
$UserKeyASCIIS = array();
for ($i = 0; $i < $n; $i++) {
$UserKeyASCIIS[] = ord(substr($UserKey, $i, 1));
}
$TextASCIIS = array();
for ($l = 0; $l < strlen($str); $l++) {
$TextASCIIS[] = ord(substr($str, $l, 1));
}
if ($mode == "E") {
for ($j = 0; $j < strlen($str); $j++) {
$k = ($k + 1 >= $n) ? 1 : $k + 1;
$temp = $TextASCIIS[$j] + $UserKeyASCIIS[$k];
if ($temp > 255) {
$temp = $temp - 255;
}
$var.= chr($temp);
}
}
if ($mode == "D") {
for ($j = 0; $j < strlen($str); $j++) {
$k = ($k + 1 >= $n) ? 1 : $k + 1;
$temp = $TextASCIIS[$j] - $UserKeyASCIIS[$k];
//echo $temp."-";
if ($temp < 0) {
$temp = $temp + 255;
}
$var.= chr($temp);
}
}
return $var;
}
Pero me funciona solo para encriptar el desencriptar no me funciona :(