dzx1.5加解密函数authcode分享

<?php
$authkey = '';
/**
 * @param string $string: 输入的需要加密（或解密）的明文（或密文）
 * @param string $operation: 'DECODE'或其它，其中默认表示解密，输入其它表示加密
 * @param string $key: 加解密密钥
 * @param int $expiry: 有效期
 */
function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) {
	global $authkey;
	$ckey_length = 4;
	$key = md5($key != '' ? $key : $authkey);
	$keya = md5(substr($key, 0, 16));
	$keyb = md5(substr($key, 16, 16));
	$keyc = $ckey_length ? ($operation == 'DECODE' ? substr($string, 0, $ckey_length): substr(md5(microtime()), -$ckey_length)) : '';

	$cryptkey = $keya.md5($keya.$keyc);
	$key_length = strlen($cryptkey);

	$string = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('%010d', $expiry ? $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string;
	$string_length = strlen($string);

	$result = '';
	$box = range(0, 255);

	$rndkey = array();
	for($i = 0; $i <= 255; $i++) {
		$rndkey[$i] = ord($cryptkey[$i % $key_length]);
	}

	for($j = $i = 0; $i < 256; $i++) {
		$j = ($j + $box[$i] + $rndkey[$i]) % 256;
		$tmp = $box[$i];
		$box[$i] = $box[$j];
		$box[$j] = $tmp;
	}

	for($a = $j = $i = 0; $i < $string_length; $i++) {
		$a = ($a + 1) % 256;
		$j = ($j + $box[$a]) % 256;
		$tmp = $box[$a];
		$box[$a] = $box[$j];
		$box[$j] = $tmp;
		$result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256]));
	}

	if($operation == 'DECODE') {
		if((substr($result, 0, 10) == 0 || substr($result, 0, 10) - time() > 0) && substr($result, 10, 16) == substr(md5(substr($result, 26).$keyb), 0, 16)) {
			return substr($result, 26);
		} else {
			return '';
		}
	} else {
		return $keyc.str_replace('=', '', base64_encode($result));
	}

}
$str = '1234';
$key = '1234';
echo "明文:".$str;
echo "
";
echo "密钥:".$key;
$encode = authcode($str,'11',$key);
echo "
";
echo "加密后的密文:".$encode;
echo "
";
$decode = authcode($encode,'DECODE',$key);
echo "解密后的明文:".$decode;
/*End of php*/