本篇文章是对PHP写的加密函数且支持私人密钥进行了详细的分析介绍，需要的朋友参考下

在开发PHP系统时,会员部分往往是一个必不可少的模块,而密码的处理又是不得不面对的问题,PHP 的 Mcrypt 加密库又需要额外设置,很多人都是直接使用md5()函数加密,这个方法的确安全,但是因为md5是不可逆加密,无法还原密码,因此也有一些不便之处,本文介绍加密函数支持私钥,用起来还是不错的.
代码如下:
PHP:

<ol><li class="li1"><div class="de1"> </div>
</li>
<li class="li1"><div class="de1"><span class="kw2"><?php</span>
 </div>
</li>
<li class="li1"><div class="de1"><span class="co1">// 说明：PHP 写的加密函数,支持私人密钥 </span>
</div>
</li>
<li class="li1"><div class="de1"><span class="co1">// 整理：http://www.jb51.net </span>
</div>
</li>
<li class="li2"><div class="de2"> </div>
</li>
<li class="li1"><div class="de1"><span class="kw2">function</span>
 keyED<span class="br0">(</span>
<span class="re0">$txt</span>
,<span class="re0">$encrypt_key</span>
<span class="br0">)</span>
   </div>
</li>
<li class="li1"><div class="de1"><span class="br0">{</span>
   </div>
</li>
<li class="li1"><div class="de1">    <span class="re0">$encrypt_key</span>
 = <span class="kw3">md5</span>
<span class="br0">(</span>
<span class="re0">$encrypt_key</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li1"><div class="de1">    <span class="re0">$ctr</span>
=<span class="nu0">0</span>
;   </div>
</li>
<li class="li2"><div class="de2">    <span class="re0">$tmp</span>
 = <span class="st0">""</span>
;   </div>
</li>
<li class="li1"><div class="de1">    <span class="kw1">for</span>
 <span class="br0">(</span>
<span class="re0">$i</span>
=<span class="nu0">0</span>
;<span class="re0">$i</span>
<strlen<span class="br0">(</span>
<span class="re0">$txt</span>
<span class="br0">)</span>
;<span class="re0">$i</span>
++<span class="br0">)</span>
   </div>
</li>
<li class="li1"><div class="de1">    <span class="br0">{</span>
   </div>
</li>
<li class="li1"><div class="de1">        <span class="kw1">if</span>
 <span class="br0">(</span>
<span class="re0">$ctr</span>
==<span class="kw3">strlen</span>
<span class="br0">(</span>
<span class="re0">$encrypt_key</span>
<span class="br0">)</span>
<span class="br0">)</span>
 <span class="re0">$ctr</span>
=<span class="nu0">0</span>
;   </div>
</li>
<li class="li1"><div class="de1">        <span class="re0">$tmp</span>
.= <span class="kw3">substr</span>
<span class="br0">(</span>
<span class="re0">$txt</span>
,<span class="re0">$i</span>
,<span class="nu0">1</span>
<span class="br0">)</span>
 ^ <span class="kw3">substr</span>
<span class="br0">(</span>
<span class="re0">$encrypt_key</span>
,<span class="re0">$ctr</span>
,<span class="nu0">1</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li2"><div class="de2">        <span class="re0">$ctr</span>
++;   </div>
</li>
<li class="li1"><div class="de1">    <span class="br0">}</span>
   </div>
</li>
<li class="li1"><div class="de1">    <span class="kw1">return</span>
 <span class="re0">$tmp</span>
;   </div>
</li>
<li class="li1"><div class="de1"><span class="br0">}</span>
   </div>
</li>
<li class="li1"><div class="de1"> </div>
</li>
<li class="li2"><div class="de2"><span class="kw2">function</span>
 encrypt<span class="br0">(</span>
<span class="re0">$txt</span>
,<span class="re0">$key</span>
<span class="br0">)</span>
   </div>
</li>
<li class="li1"><div class="de1"><span class="br0">{</span>
   </div>
</li>
<li class="li1"><div class="de1">    <span class="kw3">srand</span>
<span class="br0">(</span>
<span class="br0">(</span>
double<span class="br0">)</span>
<span class="kw3">microtime</span>
<span class="br0">(</span>
<span class="br0">)</span>
*<span class="nu0">1000000</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li1"><div class="de1">    <span class="re0">$encrypt_key</span>
 = <span class="kw3">md5</span>
<span class="br0">(</span>
<span class="kw3">rand</span>
<span class="br0">(</span>
<span class="nu0">0</span>
,<span class="nu0">32000</span>
<span class="br0">)</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li1"><div class="de1">    <span class="re0">$ctr</span>
=<span class="nu0">0</span>
;   </div>
</li>
<li class="li2"><div class="de2">    <span class="re0">$tmp</span>
 = <span class="st0">""</span>
;   </div>
</li>
<li class="li1"><div class="de1">    <span class="kw1">for</span>
 <span class="br0">(</span>
<span class="re0">$i</span>
=<span class="nu0">0</span>
;<span class="re0">$i</span>
<strlen<span class="br0">(</span>
<span class="re0">$txt</span>
<span class="br0">)</span>
;<span class="re0">$i</span>
++<span class="br0">)</span>
   </div>
</li>
<li class="li1"><div class="de1">    <span class="br0">{</span>
   </div>
</li>
<li class="li1"><div class="de1">        <span class="kw1">if</span>
 <span class="br0">(</span>
<span class="re0">$ctr</span>
==<span class="kw3">strlen</span>
<span class="br0">(</span>
<span class="re0">$encrypt_key</span>
<span class="br0">)</span>
<span class="br0">)</span>
 <span class="re0">$ctr</span>
=<span class="nu0">0</span>
;   </div>
</li>
<li class="li1"><div class="de1">        <span class="re0">$tmp</span>
.= <span class="kw3">substr</span>
<span class="br0">(</span>
<span class="re0">$encrypt_key</span>
,<span class="re0">$ctr</span>
,<span class="nu0">1</span>
<span class="br0">)</span>
 . <span class="br0">(</span>
<span class="kw3">substr</span>
<span class="br0">(</span>
<span class="re0">$txt</span>
,<span class="re0">$i</span>
,<span class="nu0">1</span>
<span class="br0">)</span>
 ^ <span class="kw3">substr</span>
<span class="br0">(</span>
<span class="re0">$encrypt_key</span>
,<span class="re0">$ctr</span>
,<span class="nu0">1</span>
<span class="br0">)</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li2"><div class="de2">        <span class="re0">$ctr</span>
++;   </div>
</li>
<li class="li1"><div class="de1">    <span class="br0">}</span>
   </div>
</li>
<li class="li1"><div class="de1">    <span class="kw1">return</span>
 keyED<span class="br0">(</span>
<span class="re0">$tmp</span>
,<span class="re0">$key</span>
<span class="br0">)</span>
; </div>
</li>
<li class="li1"><div class="de1"><span class="br0">}</span>
   </div>
</li>
<li class="li1"><div class="de1"> </div>
</li>
<li class="li2"><div class="de2"><span class="kw2">function</span>
 decrypt<span class="br0">(</span>
<span class="re0">$txt</span>
,<span class="re0">$key</span>
<span class="br0">)</span>
   </div>
</li>
<li class="li1"><div class="de1"><span class="br0">{</span>
   </div>
</li>
<li class="li1"><div class="de1">    <span class="re0">$txt</span>
 = keyED<span class="br0">(</span>
<span class="re0">$txt</span>
,<span class="re0">$key</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li1"><div class="de1">    <span class="re0">$tmp</span>
 = <span class="st0">""</span>
;   </div>
</li>
<li class="li1"><div class="de1">    <span class="kw1">for</span>
 <span class="br0">(</span>
<span class="re0">$i</span>
=<span class="nu0">0</span>
;<span class="re0">$i</span>
<strlen<span class="br0">(</span>
<span class="re0">$txt</span>
<span class="br0">)</span>
;<span class="re0">$i</span>
++<span class="br0">)</span>
   </div>
</li>
<li class="li2"><div class="de2">    <span class="br0">{</span>
   </div>
</li>
<li class="li1"><div class="de1">        <span class="re0">$md5</span>
 = <span class="kw3">substr</span>
<span class="br0">(</span>
<span class="re0">$txt</span>
,<span class="re0">$i</span>
,<span class="nu0">1</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li1"><div class="de1">        <span class="re0">$i</span>
++;   </div>
</li>
<li class="li1"><div class="de1">        <span class="re0">$tmp</span>
.= <span class="br0">(</span>
<span class="kw3">substr</span>
<span class="br0">(</span>
<span class="re0">$txt</span>
,<span class="re0">$i</span>
,<span class="nu0">1</span>
<span class="br0">)</span>
 ^ <span class="re0">$md5</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li1"><div class="de1">    <span class="br0">}</span>
   </div>
</li>
<li class="li2"><div class="de2">    <span class="kw1">return</span>
 <span class="re0">$tmp</span>
;   </div>
</li>
<li class="li1"><div class="de1"><span class="br0">}</span>
  </div>
</li>
<li class="li1"><div class="de1"> </div>
</li>
<li class="li1"><div class="de1"><span class="re0">$key</span>
 = <span class="st0">"www.yitu.org"</span>
;   </div>
</li>
<li class="li1"><div class="de1"><span class="re0">$string</span>
 = <span class="st0">"我是加密字符"</span>
;   </div>
</li>
<li class="li2"><div class="de2"> </div>
</li>
<li class="li1"><div class="de1"><span class="co1">// encrypt $string, and store it in $enc_text   </span>
</div>
</li>
<li class="li1"><div class="de1"><span class="re0">$enc_text</span>
 = encrypt<span class="br0">(</span>
<span class="re0">$string</span>
,<span class="re0">$key</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li1"><div class="de1"> </div>
</li>
<li class="li1"><div class="de1"><span class="co1">// decrypt the encrypted text $enc_text, and store it in $dec_text   </span>
</div>
</li>
<li class="li2"><div class="de2"><span class="re0">$dec_text</span>
 = decrypt<span class="br0">(</span>
<span class="re0">$enc_text</span>
,<span class="re0">$key</span>
<span class="br0">)</span>
;   </div>
</li>
<li class="li1"><div class="de1"> </div>
</li>
<li class="li1"><div class="de1"><span class="kw3">print</span>
 <span class="st0">"加密的 text : $enc_text <Br> "</span>
;   </div>
</li>
<li class="li1"><div class="de1"><span class="kw3">print</span>
 <span class="st0">"解密的 text : $dec_text <Br> "</span>
;   </div>
</li>
<li class="li1"><div class="de1"><span class="kw2">?></span>
 </div>
</li>
<li class="li2"><div class="de2"> </div>
</li>
</ol>

每一次加密后的结果是不一样的,大大加强了密码的安全性.