PHP 动态加密解密

<?php 

function encrypt($txt,$key){
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.";
    $ikey ="-bear-x6g6ZWm2G9gq3kRIxsZ6_vr0Bo.pOrm";
    $nh1 = rand(0,64);
    $nh2 = rand(0,64);
    $nh3 = rand(0,64);
    $ch1 = $chars{$nh1};
    $ch2 = $chars{$nh2};
    $ch3 = $chars{$nh3};
    $nhnum = $nh1 + $nh2 + $nh3;
    $knum = 0;$i = 0;
    while(isset($key{$i})) $knum +=ord($key{$i++});
    $mdKey = substr(md5(md5(md5($key.$ch1).$ch2.$ikey).$ch3),$nhnum%8,$knum%8 + 16);
    $txt = base64_encode($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;

    }
function decrypt($txt,$key)
    {
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.";
    $ikey ="-bear-x6g6ZWm2G9gq3kRIxsZ6_vr0Bo.pOrm";
    $knum = 0;$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);
    return trim(base64_decode($tmp));
    }

$key    = '1qaz2wsx';
$name = encrypt('120320',$key);
echo $name;
echo '<br />';
$rename = decrypt($name,$key);
echo $rename;
        
?>