//加密/可解密函数(要知道解密key才能解密)
function passport_encrypt($txt, $key){
    srand((double)microtime() * 1000000);
    $encrypt_key = md5(rand(0, 32000));
    $ctr = 0;
    $tmp = '';
    for($i = 0;$i < strlen($txt); $i++){
    $ctr = $ctr == strlen($encrypt_key) ? 0 : $ctr;
    $tmp .= $encrypt_key[$ctr].($txt[$i] ^ $encrypt_key[$ctr++]);
    }
    return base64_encode(passport_key($tmp, $key));
}

function passport_decrypt($txt, $key){
    $txt = passport_key(base64_decode($txt), $key);
    $tmp = '';
    for($i = 0;$i < strlen($txt); $i++){
    $md5 = $txt[$i];
    $tmp .= $txt[++$i] ^ $md5;
    }
    return $tmp;
}