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<h2 class="title">Encryption Filters</h2>
<p class="simpara">
<em>mcrypt.*</em> and <em>mdecrypt.*</em>
provide symmetric encryption and decryption using libmcrypt.
Both sets of filters support the same algorithms available to
<a href="ref.mcrypt.html" class="link">mcrypt extension</a> in the form of
<em>mcrypt.ciphername</em> where <em><code class="parameter">ciphername</code></em>
is the name of the cipher as it would be passed to
<span class="function"><a href="function.mcrypt-module-open.html" class="function">mcrypt_module_open()</a></span>.
The following five filter parameters are also available:
</p>
<p class="para">
<table class="doctable table">
<caption><strong>mcrypt filter parameters</strong></caption>
<thead>
<tr>
<th>Parameter</th>
<th>Required?</th>
<th>Default</th>
<th>Sample Values</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>mode</td>
<td>Optional</td>
<td>cbc</td>
<td>cbc, cfb, ecb, nofb, ofb, stream</td>
</tr>
<tr>
<td>algorithms_dir</td>
<td>Optional</td>
<td>ini_get('mcrypt.algorithms_dir')</td>
<td>Location of algorithms modules</td>
</tr>
<tr>
<td>modes_dir</td>
<td>Optional</td>
<td>ini_get('mcrypt.modes_dir')</td>
<td>Location of modes modules</td>
</tr>
<tr>
<td>iv</td>
<td>Required</td>
<td>N/A</td>
<td>Typically 8, 16, or 32 bytes of binary data. Depends on cipher</td>
</tr>
<tr>
<td>key</td>
<td>Required</td>
<td>N/A</td>
<td>Typically 8, 16, or 32 bytes of binary data. Depends on cipher</td>
</tr>
</tbody>
</table>
</p>
<div class="example" id="example-5639">
<p><strong>Example #1 Encrypting file output using 3DES</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$passphrase </span><span style="color: #007700">= </span><span style="color: #DD0000">'My secret'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">/* Turn a human readable passphrase<br /> * into a reproducable iv/key pair<br /> */<br /></span><span style="color: #0000BB">$iv </span><span style="color: #007700">= </span><span style="color: #0000BB">substr</span><span style="color: #007700">(</span><span style="color: #0000BB">md5</span><span style="color: #007700">(</span><span style="color: #DD0000">'iv'</span><span style="color: #007700">.</span><span style="color: #0000BB">$passphrase</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">), </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">8</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$key </span><span style="color: #007700">= </span><span style="color: #0000BB">substr</span><span style="color: #007700">(</span><span style="color: #0000BB">md5</span><span style="color: #007700">(</span><span style="color: #DD0000">'pass1'</span><span style="color: #007700">.</span><span style="color: #0000BB">$passphrase</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">) . <br /> </span><span style="color: #0000BB">md5</span><span style="color: #007700">(</span><span style="color: #DD0000">'pass2'</span><span style="color: #007700">.</span><span style="color: #0000BB">$passphrase</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">), </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">24</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$opts </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'iv'</span><span style="color: #007700">=></span><span style="color: #0000BB">$iv</span><span style="color: #007700">, </span><span style="color: #DD0000">'key'</span><span style="color: #007700">=></span><span style="color: #0000BB">$key</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$fp </span><span style="color: #007700">= </span><span style="color: #0000BB">fopen</span><span style="color: #007700">(</span><span style="color: #DD0000">'secret-file.enc'</span><span style="color: #007700">, </span><span style="color: #DD0000">'wb'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">stream_filter_append</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #DD0000">'mcrypt.tripledes'</span><span style="color: #007700">, </span><span style="color: #0000BB">STREAM_FILTER_WRITE</span><span style="color: #007700">, </span><span style="color: #0000BB">$opts</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">fwrite</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #DD0000">'Secret secret secret data'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">fclose</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<div class="example" id="example-5640">
<p><strong>Example #2 Reading an encrypted file</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$passphrase </span><span style="color: #007700">= </span><span style="color: #DD0000">'My secret'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">/* Turn a human readable passphrase<br /> * into a reproducable iv/key pair<br /> */<br /></span><span style="color: #0000BB">$iv </span><span style="color: #007700">= </span><span style="color: #0000BB">substr</span><span style="color: #007700">(</span><span style="color: #0000BB">md5</span><span style="color: #007700">(</span><span style="color: #DD0000">'iv'</span><span style="color: #007700">.</span><span style="color: #0000BB">$passphrase</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">), </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">8</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$key </span><span style="color: #007700">= </span><span style="color: #0000BB">substr</span><span style="color: #007700">(</span><span style="color: #0000BB">md5</span><span style="color: #007700">(</span><span style="color: #DD0000">'pass1'</span><span style="color: #007700">.</span><span style="color: #0000BB">$passphrase</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">) . <br /> </span><span style="color: #0000BB">md5</span><span style="color: #007700">(</span><span style="color: #DD0000">'pass2'</span><span style="color: #007700">.</span><span style="color: #0000BB">$passphrase</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">), </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">24</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$opts </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'iv'</span><span style="color: #007700">=></span><span style="color: #0000BB">$iv</span><span style="color: #007700">, </span><span style="color: #DD0000">'key'</span><span style="color: #007700">=></span><span style="color: #0000BB">$key</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$fp </span><span style="color: #007700">= </span><span style="color: #0000BB">fopen</span><span style="color: #007700">(</span><span style="color: #DD0000">'secret-file.enc'</span><span style="color: #007700">, </span><span style="color: #DD0000">'rb'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">stream_filter_append</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #DD0000">'mdecrypt.tripledes'</span><span style="color: #007700">, </span><span style="color: #0000BB">STREAM_FILTER_READ</span><span style="color: #007700">, </span><span style="color: #0000BB">$opts</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$data </span><span style="color: #007700">= </span><span style="color: #0000BB">rtrim</span><span style="color: #007700">(</span><span style="color: #0000BB">stream_get_contents</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">fclose</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">);<br /><br />echo </span><span style="color: #0000BB">$data</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
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