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<title>Encrypted Storage Model</title>
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<h2 class="title">Encrypted Storage Model</h2>
<p class="simpara">
SSL/SSH protects data travelling from the client to the server: SSL/SSH
does not protect persistent data stored in a database. SSL is an
on-the-wire protocol.
</p>
<p class="simpara">
Once an attacker gains access to your database directly (bypassing the
webserver), stored sensitive data may be exposed or misused, unless
the information is protected by the database itself. Encrypting the data
is a good way to mitigate this threat, but very few databases offer this
type of data encryption.
</p>
<p class="simpara">
The easiest way to work around this problem is to first create your own
encryption package, and then use it from within your <acronym title="PHP: Hypertext Preprocessor">PHP</acronym> scripts. <acronym title="PHP: Hypertext Preprocessor">PHP</acronym>
can assist you in this with several extensions, such as <a href="ref.mcrypt.html" class="link">Mcrypt</a> and <a href="ref.mhash.html" class="link">Mhash</a>, covering a wide variety of encryption
algorithms. The script encrypts the data before inserting it into the database, and decrypts
it when retrieving. See the references for further examples of how
encryption works.
</p>
<p class="simpara">
In the case of truly hidden data, if its raw representation is not needed
(i.e. will not be displayed), hashing may also be taken into consideration.
The well-known example for hashing is storing the cryptographic hash of a
password in a database, instead of the password itself. See also
<span class="function"><a href="function.crypt.html" class="function">crypt()</a></span>.
</p>
<div class="example" id="example-333">
<p><strong>Example #1 Using hashed password field</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #FF8000">// storing password hash<br />// $random_chars retrieved e.g. using /dev/random<br /></span><span style="color: #0000BB">$query </span><span style="color: #007700">= </span><span style="color: #0000BB">sprintf</span><span style="color: #007700">(</span><span style="color: #DD0000">"INSERT INTO users(name,pwd) VALUES('%s','%s');"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">pg_escape_string</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">),<br /> </span><span style="color: #0000BB">pg_escape_string</span><span style="color: #007700">(</span><span style="color: #0000BB">crypt</span><span style="color: #007700">(</span><span style="color: #0000BB">$password</span><span style="color: #007700">, </span><span style="color: #DD0000">'$2a$07$' </span><span style="color: #007700">. </span><span style="color: #0000BB">$random_chars </span><span style="color: #007700">. </span><span style="color: #DD0000">'$'</span><span style="color: #007700">)));<br /></span><span style="color: #0000BB">$result </span><span style="color: #007700">= </span><span style="color: #0000BB">pg_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$connection</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// querying if user submitted the right password<br /></span><span style="color: #0000BB">$query </span><span style="color: #007700">= </span><span style="color: #0000BB">sprintf</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT pwd FROM users WHERE name='%s';"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">pg_escape_string</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$row </span><span style="color: #007700">= </span><span style="color: #0000BB">pg_fetch_assoc</span><span style="color: #007700">(</span><span style="color: #0000BB">pg_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$connection</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">));<br /><br />if (</span><span style="color: #0000BB">$row </span><span style="color: #007700">&& </span><span style="color: #0000BB">crypt</span><span style="color: #007700">(</span><span style="color: #0000BB">$password</span><span style="color: #007700">, </span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #DD0000">'pwd'</span><span style="color: #007700">]) == </span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #DD0000">'pwd'</span><span style="color: #007700">]) {<br /> echo </span><span style="color: #DD0000">'Welcome, ' </span><span style="color: #007700">. </span><span style="color: #0000BB">htmlspecialchars</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">) . </span><span style="color: #DD0000">'!'</span><span style="color: #007700">;<br />} else {<br /> echo </span><span style="color: #DD0000">'Authentication failed for ' </span><span style="color: #007700">. </span><span style="color: #0000BB">htmlspecialchars</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">) . </span><span style="color: #DD0000">'.'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
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