加密解析

encrypt.php

<?php
function  strToHex($string)   
{   
      $hex="";   
      for   ($i=0;$i<strlen($string);$i++)   
      $hex.=dechex(ord($string[$i]));   
      $hex=strtoupper($hex);   
      return   $hex;   
   }   
function  hexToStr($hex)   
   {   
      $string="";   
      for   ($i=0;$i<strlen($hex)-1;$i+=2)   
      $string.=chr(hexdec($hex[$i].$hex[$i+1]));   
      return   $string;   
}


function keyED($txt,$encrypt_key){
    $encrypt_key = md5($encrypt_key);
    $ctr=0;
    $tmp = "";
    for ($i=0;$i<strlen($txt);$i++)
    {
        if ($ctr==strlen($encrypt_key)) $ctr=0;
        $tmp.= substr($txt,$i,1) ^ substr($encrypt_key,$ctr,1);
        $ctr++;
    }
    return $tmp;
}
function encrypt($txt,$key){
    srand((double)microtime()*1000000);
    $encrypt_key = md5(rand(0,32000));
    $ctr=0;
    $tmp = "";
    for ($i=0;$i<strlen($txt);$i++)
    {
        if ($ctr==strlen($encrypt_key)) $ctr=0;
        $tmp.= substr($encrypt_key,$ctr,1) .
            (substr($txt,$i,1) ^ substr($encrypt_key,$ctr,1));
        $ctr++;
    }
    $ret=strtohex(base64_encode(keyED($tmp,$key)));
    return substr(md5($ret.$key),0,8).$ret;
}
function decrypt($txt,$key){
    //先检验校验码在不在;
    $first_8chars = substr($txt,0,8);
    $last_chars = substr($txt,8);
    $md5_verifier = substr(md5($last_chars.$key),0,8);
    if($md5_verifier !=$first_8chars){
        return "";
    }
    $txt = $last_chars;
    $txt=base64_decode(hextostr($txt));
    $txt = keyED($txt,$key);
    $tmp = "";
    for ($i=0;$i<strlen($txt);$i++)
    {
        $md5 = substr($txt,$i,1);
        $i++;
        $tmp.= (substr($txt,$i,1) ^ $md5);
    }
    return $tmp;
}
/**
//$key="ooomygod这是一个密阴goooo";
$key="o8342-hfsjfrr3rfs'fgtfjhnbffds'ghfwfrbvdsfsfjhssf'dsfs";
$string = "需要加密的字符串，如密码等.";
// 开始加密 encrypt $string, and store it in $enc_text
$enc_text = encrypt($string,$key);
// 开始解密 decrypt the encrypted text $enc_text, and store it in $dec_text
$dec_text = decrypt($enc_text,$key);
print "原始字符串 : $string <Br>\n";
print "加密后字串 : $enc_text <Br>\n";
print "解密后字串 : $dec_text <Br>\n";
print "to decode:";
print decrypt("78123be0417539566D515055552B38446F4172575562514A6777616B564F4A5A3851614355374E576E774F42564C42512B565753566555412B464C7857754E5336675332412B3447365153505537525438675456564C634F6F414B415665494439464F47412B454B2B6C48594353633Ds",$key);
 */
?>