<?php
/*
 * Common encryption functions
 * 
 * Allow for more advanced encryption using the random seed set in the
 * configuration.   
 */
function get_rnd_iv($iv_len) {
	$iv = '';
	while ($iv_len-- > 0) {
		$iv .= chr(mt_rand() & 0xff);
	}
	return $iv;
}
function md5_encrypt($plain_text, $password, $iv_len = 16) {
	$plain_text .= "\x13";
	$n = strlen($plain_text);
	if ($n % 16) $plain_text .= str_repeat("\0", 16 - ($n % 16));
	$i = 0;
	$enc_text = get_rnd_iv($iv_len);
	$iv = substr($password ^ $enc_text, 0, 512);
	while ($i < $n) {
		$block = substr($plain_text, $i, 16) ^ pack('H*', md5($iv));
		$enc_text .= $block;
		$iv = substr($block . $iv, 0, 512) ^ $password;
		$i += 16;
	}
	return base64_encode($enc_text);
}
function md5_decrypt($enc_text, $password, $iv_len = 16) {
	$enc_text = base64_decode($enc_text);
	$n = strlen($enc_text);
	$i = $iv_len;
	$plain_text = '';
	$iv = substr($password ^ substr($enc_text, 0, $iv_len), 0, 512);
	while ($i < $n) {
		$block = substr($enc_text, $i, 16);
		$plain_text .= $block ^ pack('H*', md5($iv));
		$iv = substr($block . $iv, 0, 512) ^ $password;
		$i += 16;
	}
	return preg_replace('/\\x13\\x00*$/', '', $plain_text);
}
?>