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/**
 * 常用對稱加密演算法類
 * 支援金鑰：64/128/256 bit（位元組長度8/16/32）
 * 支援演算法：DES/AES（根據金鑰長度自動匹配使用：DES:64bit AES:128/256bit）
 * 支援模式：CBC/ECB/OFB/CFB
 * 密文編碼：base64字串/十六進位制字串/二進位制字串流
 * 填充方式: PKCS5Padding（DES）
 *
 * @author: linvo
 * @version: 1.0.0
 * @date: 2013/1/10
 */
class Xcrypt{

    private $mcrypt;
    private $key;
    private $mode;
    private $iv;
    private $blocksize;

    /**
     * 建構函式
     *
     * @param string 金鑰
     * @param string 模式
     * @param string 向量（"off":不使用 / "auto":自動 / 其他:指定值，長度同金鑰）
     */
    public function __construct($key, $mode = 'cbc', $iv = "off"){
        switch (strlen($key)){
        case 8:
            $this->mcrypt = MCRYPT_DES;
            break;
        case 16:
            $this->mcrypt = MCRYPT_RIJNDAEL_128;
            break;
        case 32:
            $this->mcrypt = MCRYPT_RIJNDAEL_256;
            break;
        default:
            die("Key size must be 8/16/32");
        }

        $this->key = $key;

        switch (strtolower($mode)){
        case 'ofb':
            $this->mode = MCRYPT_MODE_OFB;
            if ($iv == 'off') die('OFB must give a IV'); //OFB必須有向量
            break;
        case 'cfb':
            $this->mode = MCRYPT_MODE_CFB;
            if ($iv == 'off') die('CFB must give a IV'); //CFB必須有向量
            break;
        case 'ecb':
            $this->mode = MCRYPT_MODE_ECB;
            $iv = 'off'; //ECB不需要向量
            break;
        case 'cbc':
        default:
            $this->mode = MCRYPT_MODE_CBC;
        }

        switch (strtolower($iv)){
        case "off":
            $this->iv = null;
            break;
        case "auto":
            $source = PHP_OS=='WINNT' ? MCRYPT_RAND : MCRYPT_DEV_RANDOM;
            $this->iv = mcrypt_create_iv(mcrypt_get_block_size($this->mcrypt, $this->mode), $source);
            break;
        default:
            $this->iv = $iv;
        }

   
    }


    /**
     * 獲取向量值
     * @param string 向量值編碼（base64/hex/bin）
     * @return string 向量值
     */
    public function getIV($code = 'base64'){
        switch ($code){
        case 'base64':
            $ret = base64_encode($this->iv);
            break;
        case 'hex':
            $ret = bin2hex($this->iv);
            break;
        case 'bin':
        default:
            $ret = $this->iv;
        }
        return $ret;
    }


    /**
     * 加密
     * @param string 明文
     * @param string 密文編碼（base64/hex/bin）
     * @return string 密文
     */
    public function encrypt($str, $code = 'base64'){
        if ($this->mcrypt == MCRYPT_DES) $str = $this->_pkcs5Pad($str);

        if (isset($this->iv)) {
            $result = mcrypt_encrypt($this->mcrypt, $this->key, $str, $this->mode, $this->iv);  
        } else {
            @$result = mcrypt_encrypt($this->mcrypt, $this->key, $str, $this->mode);  
        }

        switch ($code){
        case 'base64':
            $ret = base64_encode($result);
            break;
        case 'hex':
            $ret = bin2hex($result);
            break;
        case 'bin':
        default:
            $ret = $result;
        }
 
        return $ret;
 
    }

    /**
     * 解密 
     * @param string 密文
     * @param string 密文編碼（base64/hex/bin）
     * @return string 明文
     */
    public function decrypt($str, $code = "base64"){    
        $ret = false;

        switch ($code){
        case 'base64':
            $str = base64_decode($str);
            break;
        case 'hex':
            $str = $this->_hex2bin($str);
            break;
        case 'bin':
        default:
        }

        if ($str !== false){
            if (isset($this->iv)) {
                $ret = mcrypt_decrypt($this->mcrypt, $this->key, $str, $this->mode, $this->iv);  
            } else {
                @$ret = mcrypt_decrypt($this->mcrypt, $this->key, $str, $this->mode);  
            }
            if ($this->mcrypt == MCRYPT_DES) $ret = $this->_pkcs5Unpad($ret);
            $ret = trim($ret);
        }

        return $ret; 
    } 



    private function _pkcs5Pad($text){
        $this->blocksize = mcrypt_get_block_size($this->mcrypt, $this->mode);  
        $pad = $this->blocksize - (strlen($text) % $this->blocksize);
        return $text . str_repeat(chr($pad), $pad);
    }

    private function _pkcs5Unpad($text){
        $pad = ord($text{strlen($text) - 1});
        if ($pad > strlen($text)) return false;
        if (strspn($text, chr($pad), strlen($text) - $pad) != $pad) return false;
        $ret = substr($text, 0, -1 * $pad);
        return $ret;
    }

    private function _hex2bin($hex = false){
        $ret = $hex !== false && preg_match('/^[0-9a-fA-F]+$/i', $hex) ? pack("H*", $hex) : false;    
        return $ret;
    }



}
 

<?php
header('Content-Type:text/html;Charset=utf-8;');

include "xcrypt.php";

echo '<pre>';
//////////////////////////////////////
$a = isset($_GET['a']) ? $_GET['a'] : '測試123';

//金鑰
$key = '12345678123456781234567812345678'; //256 bit
$key = '1234567812345678'; //128 bit
$key = '12345678'; //64 bit

//設定模式和IV
$m = new Xcrypt($key, 'cbc', 'auto');

//獲取向量值
echo '向量：';
var_dump($m->getIV());

//加密
$b = $m->encrypt($a, 'base64');
//解密
$c = $m->decrypt($b, 'base64');

echo '加密後：';
var_dump($b);
echo '解密後：';
var_dump($c);


/////////////////////////////////////////
echo '</pre>';