加密函数和解密函数

1 加密函数

/**
 * 作用：加密函数
 * @ param  string  $txt      需要加密的字符串
 * @ param  string  $key      密钥
 * @ return string            返回加密结果
 * MD5_KEY                    是自己在配置文件中定义的KEY
 */

function encrypt($txt, $key = '')
{
    if(empty($txt)){
        return $txt;
    } 
    if(empty($key)){
        $key = md5(MD5_KEY);
    } 
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.";
    $ikey ="-x6g6ZWm2G9g_vr0Bo.pOq3kRIxsZ6rm";
    // 返回0-64之间的随机整数
    $nh1 = rand(0,64);
    $nh2 = rand(0,64);
    $nh3 = rand(0,64);
    // 根据随机数获取指定位置的字符
    $ch1 = $chars{$nh1};
    $ch2 = $chars{$nh2};
    $ch3 = $chars{$nh3};
    // 随机数相加
    $nhnum = $nh1 + $nh2 + $nh3;
    $knum = 0;
    $i = 0;
    // ord函数返回字符串首个字符的ASCII值。
    while(isset($key{$i})){
        $knum +=ord($key{$i++});
    } 

    $mdKey = substr(md5(md5(md5($key.$ch1).$ch2.$ikey).$ch3), $nhnum%8, $knum%8 + 16);
    $txt = base64_encode(time().'_'.$txt);
    $txt = str_replace(array('+','/','='),array('-','_','.'),$txt);
    $tmp = '';
    $j=0;$k = 0;
    $tlen = strlen($txt);
    $klen = strlen($mdKey);
    for ($i=0; $i<$tlen; $i++) {
        $k = $k == $klen ? 0 : $k;
        $j = ($nhnum+strpos($chars,$txt{$i})+ord($mdKey{$k++}))%64;
        $tmp .= $chars{$j};
    }

    $tmplen = strlen($tmp);
    $tmp = substr_replace($tmp,$ch3,$nh2 % ++$tmplen,0);
    $tmp = substr_replace($tmp,$ch2,$nh1 % ++$tmplen,0);
    $tmp = substr_replace($tmp,$ch1,$knum % ++$tmplen,0);
    return $tmp;
}

2 解密函数

/**
 * 解密函数
 * @ param  string $txt  需要解密的字符串
 * @ param  string $key  密匙
 * @ return string       字符串类型的返回结果
 */

function decrypt($txt, $key = '', $ttl = 0)
{
    if(empty($txt)){
        return $txt;
    } 

    if(empty($key)){
       $key = md5(MD5_KEY); 
    }

    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.";
    $ikey ="-x6g6ZWm2G9g_vr0Bo.pOq3kRIxsZ6rm";
    $knum = 0;
    $i = 0;
    $tlen = @strlen($txt);


    while(isset($key{$i})){
        $knum +=ord($key{$i++});
    } 

    $ch1 = @$txt{$knum % $tlen};
    $nh1 = strpos($chars,$ch1);
    $txt = @substr_replace($txt,'',$knum % $tlen--,1);
    $ch2 = @$txt{$nh1 % $tlen};
    $nh2 = @strpos($chars,$ch2);
    $txt = @substr_replace($txt,'',$nh1 % $tlen--,1);
    $ch3 = @$txt{$nh2 % $tlen};
    $nh3 = @strpos($chars,$ch3);
    $txt = @substr_replace($txt,'',$nh2 % $tlen--,1);
    $nhnum = $nh1 + $nh2 + $nh3;
    $mdKey = substr(md5(md5(md5($key.$ch1).$ch2.$ikey).$ch3),$nhnum % 8,$knum % 8 + 16);
    $tmp = '';
    $j=0; $k = 0;
    $tlen = @strlen($txt);
    $klen = @strlen($mdKey);
    for ($i=0; $i<$tlen; $i++) {
        $k = $k == $klen ? 0 : $k;
        $j = strpos($chars,$txt{$i})-$nhnum - ord($mdKey{$k++});
        while ($j<0) $j+=64;
        $tmp .= $chars{$j};
    }

    $tmp = str_replace(array('-','_','.'),array('+','/','='),$tmp);
    $tmp = trim(base64_decode($tmp));
    if (preg_match("/\d{10}_/s",substr($tmp,0,11))){
        if ($ttl > 0 && (time() - substr($tmp,0,11) > $ttl)){
            $tmp = null;
        }else{
            $tmp = substr($tmp,11);
        }
    }

    return $tmp;
}