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- <div class="section" id="encryption-library">
-<h1>Encryption Library<a class="headerlink" href="#encryption-library" title="Permalink to this headline">¶</a></h1>
-<div class="admonition important">
-<p class="first admonition-title">Important</p>
-<p class="last">DO NOT use this or any other <em>encryption</em> library for
-user password storage! Passwords must be <em>hashed</em> instead, and you
-should do that via PHP’s own <a class="reference external" href="http://php.net/password">Password Hashing extension</a>.</p>
-</div>
-<p>The Encryption Library provides two-way data encryption. To do so in
-a cryptographically secure way, it utilizes PHP extensions that are
-unfortunately not always available on all systems.
-You must meet one of the following dependencies in order to use this
-library:</p>
-<ul class="simple">
-<li><a class="reference external" href="http://php.net/openssl">OpenSSL</a></li>
-<li><a class="reference external" href="http://php.net/mcrypt">MCrypt</a> (and <cite>MCRYPT_DEV_URANDOM</cite> availability)</li>
-</ul>
-<p>If neither of the above dependencies is met, we simply cannot offer
-you a good enough implementation to meet the high standards required
-for proper cryptography.</p>
-<div class="contents local topic" id="contents">
-<ul class="simple">
-<li><a class="reference internal" href="#using-the-encryption-library" id="id2">Using the Encryption Library</a><ul>
-<li><a class="reference internal" href="#initializing-the-class" id="id3">Initializing the Class</a></li>
-<li><a class="reference internal" href="#default-behavior" id="id4">Default behavior</a></li>
-<li><a class="reference internal" href="#setting-your-encryption-key" id="id5">Setting your encryption_key</a></li>
-<li><a class="reference internal" href="#supported-encryption-ciphers-and-modes" id="id6">Supported encryption ciphers and modes</a><ul>
-<li><a class="reference internal" href="#portable-ciphers" id="id7">Portable ciphers</a></li>
-<li><a class="reference internal" href="#driver-specific-ciphers" id="id8">Driver-specific ciphers</a></li>
-<li><a class="reference internal" href="#encryption-modes" id="id9">Encryption modes</a></li>
-</ul>
-</li>
-<li><a class="reference internal" href="#message-length" id="id10">Message Length</a></li>
-<li><a class="reference internal" href="#configuring-the-library" id="id11">Configuring the library</a></li>
-<li><a class="reference internal" href="#encrypting-and-decrypting-data" id="id12">Encrypting and decrypting data</a><ul>
-<li><a class="reference internal" href="#how-it-works" id="id13">How it works</a></li>
-<li><a class="reference internal" href="#using-custom-parameters" id="id14">Using custom parameters</a></li>
-<li><a class="reference internal" href="#supported-hmac-authentication-algorithms" id="id15">Supported HMAC authentication algorithms</a></li>
-</ul>
-</li>
-</ul>
-</li>
-<li><a class="reference internal" href="#class-reference" id="id16">Class Reference</a></li>
-</ul>
-</div>
-<div class="custom-index container"></div><div class="section" id="using-the-encryption-library">
-<h2><a class="toc-backref" href="#id2">Using the Encryption Library</a><a class="headerlink" href="#using-the-encryption-library" title="Permalink to this headline">¶</a></h2>
-<div class="section" id="initializing-the-class">
-<h3><a class="toc-backref" href="#id3">Initializing the Class</a><a class="headerlink" href="#initializing-the-class" title="Permalink to this headline">¶</a></h3>
-<p>Like most other classes in CodeIgniter, the Encryption library is
-initialized in your controller using the <code class="docutils literal"><span class="pre">$this-&gt;load-&gt;library()</span></code>
-method:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">load</span><span class="o">-&gt;</span><span class="na">library</span><span class="p">(</span><span class="s1">&#39;encryption&#39;</span><span class="p">);</span>
-</pre></div>
-</div>
-<p>Once loaded, the Encryption library object will be available using:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span>
-</pre></div>
-</div>
-</div>
-<div class="section" id="default-behavior">
-<h3><a class="toc-backref" href="#id4">Default behavior</a><a class="headerlink" href="#default-behavior" title="Permalink to this headline">¶</a></h3>
-<p>By default, the Encryption Library will use the AES-128 cipher in CBC
-mode, using your configured <em>encryption_key</em> and SHA512 HMAC authentication.</p>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">AES-128 is chosen both because it is proven to be strong and
-because of its wide availability across different cryptographic
-software and programming languages’ APIs.</p>
-</div>
-<p>However, the <em>encryption_key</em> is not used as is.</p>
-<p>If you are somewhat familiar with cryptography, you should already know
-that a HMAC also requires a secret key and using the same key for both
-encryption and authentication is a bad practice.</p>
-<p>Because of that, two separate keys are derived from your already configured
-<em>encryption_key</em>: one for encryption and one for authentication. This is
-done via a technique called <a class="reference external" href="http://en.wikipedia.org/wiki/HKDF">HMAC-based Key Derivation Function</a> (HKDF).</p>
-</div>
-<div class="section" id="setting-your-encryption-key">
-<h3><a class="toc-backref" href="#id5">Setting your encryption_key</a><a class="headerlink" href="#setting-your-encryption-key" title="Permalink to this headline">¶</a></h3>
-<p>An <em>encryption key</em> is a piece of information that controls the
-cryptographic process and permits a plain-text string to be encrypted,
-and afterwards - decrypted. It is the secret “ingredient” in the whole
-process that allows you to be the only one who is able to decrypt data
-that you’ve decided to hide from the eyes of the public.
-After one key is used to encrypt data, that same key provides the <strong>only</strong>
-means to decrypt it, so not only must you chose one carefully, but you
-must not lose it or you will also lose access to the data.</p>
-<p>It must be noted that to ensure maximum security, such key <em>should</em> not
-only be as strong as possible, but also often changed. Such behavior
-however is rarely practical or possible to implement, and that is why
-CodeIgniter gives you the ability to configure a single key that is to be
-used (almost) every time.</p>
-<p>It goes without saying that you should guard your key carefully. Should
-someone gain access to your key, the data will be easily decrypted. If
-your server is not totally under your control it’s impossible to ensure
-key security so you may want to think carefully before using it for
-anything that requires high security, like storing credit card numbers.</p>
-<p>Your encryption key <strong>must</strong> be as long as the encyption algorithm in use
-allows. For AES-128, that’s 128 bits or 16 bytes (charcters) long.
-You will find a table below that shows the supported key lengths of
-different ciphers.</p>
-<p>The key should be as random as possible and it <strong>must not</strong> be a regular
-text string, nor the output of a hashing function, etc. In order to create
-a proper key, you must use the Encryption library’s <code class="docutils literal"><span class="pre">create_key()</span></code> method</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// $key will be assigned a 16-byte (128-bit) random key</span>
-<span class="nv">$key</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">create_key</span><span class="p">(</span><span class="mi">16</span><span class="p">);</span>
-</pre></div>
-</div>
-<p>The key can be either stored in your <em>application/config/config.php</em>, or
-you can design your own storage mechanism and pass the key dynamically
-when encrypting/decrypting.</p>
-<p>To save your key to your <em>application/config/config.php</em>, open the file
-and set:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$config</span><span class="p">[</span><span class="s1">&#39;encryption_key&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;YOUR KEY&#39;</span><span class="p">;</span>
-</pre></div>
-</div>
-<p>You’ll notice that the <code class="docutils literal"><span class="pre">create_key()</span></code> method outputs binary data, which
-is hard to deal with (i.e. a copy-paste may damage it), so you may use
-<code class="docutils literal"><span class="pre">bin2hex()</span></code>, <code class="docutils literal"><span class="pre">hex2bin()</span></code> or Base64-encoding to work with the key in
-a more friendly manner. For example:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Get a hex-encoded representation of the key:</span>
-<span class="nv">$key</span> <span class="o">=</span> <span class="nb">bin2hex</span><span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">create_key</span><span class="p">(</span><span class="mi">16</span><span class="p">));</span>
-
-<span class="c1">// Put the same value in your config with hex2bin(),</span>
-<span class="c1">// so that it is still passed as binary to the library:</span>
-<span class="nv">$config</span><span class="p">[</span><span class="s1">&#39;encryption_key&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="nb">hex2bin</span><span class="p">(</span><span class="o">&lt;</span><span class="nx">your</span> <span class="nx">hex</span><span class="o">-</span><span class="nx">encoded</span> <span class="nb">key</span><span class="o">&gt;</span><span class="p">);</span>
-</pre></div>
-</div>
-</div>
-<div class="section" id="supported-encryption-ciphers-and-modes">
-<span id="ciphers-and-modes"></span><h3><a class="toc-backref" href="#id6">Supported encryption ciphers and modes</a><a class="headerlink" href="#supported-encryption-ciphers-and-modes" title="Permalink to this headline">¶</a></h3>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">The terms ‘cipher’ and ‘encryption algorithm’ are interchangeable.</p>
-</div>
-<div class="section" id="portable-ciphers">
-<h4><a class="toc-backref" href="#id7">Portable ciphers</a><a class="headerlink" href="#portable-ciphers" title="Permalink to this headline">¶</a></h4>
-<p>Because MCrypt and OpenSSL (also called drivers throughout this document)
-each support different sets of encryption algorithms and often implement
-them in different ways, our Encryption library is designed to use them in
-a portable fashion, or in other words - it enables you to use them
-interchangeably, at least for the ciphers supported by both drivers.</p>
-<p>It is also implemented in a way that aims to match the standard
-implementations in other programming languages and libraries.</p>
-<p>Here’s a list of the so called “portable” ciphers, where
-“CodeIgniter name” is the string value that you’d have to pass to the
-Encryption library to use that cipher:</p>
-<table border="1" class="docutils">
-<colgroup>
-<col width="24%" />
-<col width="18%" />
-<col width="28%" />
-<col width="31%" />
-</colgroup>
-<thead valign="bottom">
-<tr class="row-odd"><th class="head">Cipher name</th>
-<th class="head">CodeIgniter name</th>
-<th class="head">Key lengths (bits / bytes)</th>
-<th class="head">Supported modes</th>
-</tr>
-</thead>
-<tbody valign="top">
-<tr class="row-even"><td>AES-128 / Rijndael-128</td>
-<td>aes-128</td>
-<td>128 / 16</td>
-<td>CBC, CTR, CFB, CFB8, OFB, ECB</td>
-</tr>
-<tr class="row-odd"><td>AES-192</td>
-<td>aes-192</td>
-<td>192 / 24</td>
-<td>CBC, CTR, CFB, CFB8, OFB, ECB</td>
-</tr>
-<tr class="row-even"><td>AES-256</td>
-<td>aes-256</td>
-<td>256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, ECB</td>
-</tr>
-<tr class="row-odd"><td>DES</td>
-<td>des</td>
-<td>56 / 7</td>
-<td>CBC, CFB, CFB8, OFB, ECB</td>
-</tr>
-<tr class="row-even"><td>TripleDES</td>
-<td>tripledes</td>
-<td>56 / 7, 112 / 14, 168 / 21</td>
-<td>CBC, CFB, CFB8, OFB</td>
-</tr>
-<tr class="row-odd"><td>Blowfish</td>
-<td>blowfish</td>
-<td>128-448 / 16-56</td>
-<td>CBC, CFB, OFB, ECB</td>
-</tr>
-<tr class="row-even"><td>CAST5 / CAST-128</td>
-<td>cast5</td>
-<td>88-128 / 11-16</td>
-<td>CBC, CFB, OFB, ECB</td>
-</tr>
-<tr class="row-odd"><td>RC4 / ARCFour</td>
-<td>rc4</td>
-<td>40-2048 / 5-256</td>
-<td>Stream</td>
-</tr>
-</tbody>
-</table>
-<div class="admonition important">
-<p class="first admonition-title">Important</p>
-<p class="last">Because of how MCrypt works, if you fail to provide a key
-with the appropriate length, you might end up using a different
-algorithm than the one configured, so be really careful with that!</p>
-</div>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">In case it isn’t clear from the above table, Blowfish, CAST5
-and RC4 support variable length keys. That is, any number in the
-shown ranges is valid, although in bit terms that only happens
-in 8-bit increments.</p>
-</div>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">Even though CAST5 supports key lengths lower than 128 bits
-(16 bytes), in fact they will just be zero-padded to the
-maximum length, as specified in <a class="reference external" href="http://tools.ietf.org/rfc/rfc2144.txt">RFC 2144</a>.</p>
-</div>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">Blowfish supports key lengths as small as 32 bits (4 bytes), but
-our tests have shown that only lengths of 128 bits (16 bytes) or
-higher are properly supported by both MCrypt and OpenSSL. It is
-also a bad practice to use such low-length keys anyway.</p>
-</div>
-</div>
-<div class="section" id="driver-specific-ciphers">
-<h4><a class="toc-backref" href="#id8">Driver-specific ciphers</a><a class="headerlink" href="#driver-specific-ciphers" title="Permalink to this headline">¶</a></h4>
-<p>As noted above, MCrypt and OpenSSL support different sets of encryption
-ciphers. For portability reasons and because we haven’t tested them
-properly, we do not advise you to use the ones that are driver-specific,
-but regardless, here’s a list of most of them:</p>
-<table border="1" class="docutils">
-<colgroup>
-<col width="15%" />
-<col width="10%" />
-<col width="32%" />
-<col width="44%" />
-</colgroup>
-<thead valign="bottom">
-<tr class="row-odd"><th class="head">Cipher name</th>
-<th class="head">Driver</th>
-<th class="head">Key lengths (bits / bytes)</th>
-<th class="head">Supported modes</th>
-</tr>
-</thead>
-<tbody valign="top">
-<tr class="row-even"><td>AES-128</td>
-<td>OpenSSL</td>
-<td>128 / 16</td>
-<td>CBC, CTR, CFB, CFB8, OFB, ECB, XTS</td>
-</tr>
-<tr class="row-odd"><td>AES-192</td>
-<td>OpenSSL</td>
-<td>192 / 24</td>
-<td>CBC, CTR, CFB, CFB8, OFB, ECB, XTS</td>
-</tr>
-<tr class="row-even"><td>AES-256</td>
-<td>OpenSSL</td>
-<td>256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, ECB, XTS</td>
-</tr>
-<tr class="row-odd"><td>Rijndael-128</td>
-<td>MCrypt</td>
-<td>128 / 16, 192 / 24, 256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-even"><td>Rijndael-192</td>
-<td>MCrypt</td>
-<td>128 / 16, 192 / 24, 256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-odd"><td>Rijndael-256</td>
-<td>MCrypt</td>
-<td>128 / 16, 192 / 24, 256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-even"><td>GOST</td>
-<td>MCrypt</td>
-<td>256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-odd"><td>Twofish</td>
-<td>MCrypt</td>
-<td>128 / 16, 192 / 24, 256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-even"><td>CAST-128</td>
-<td>MCrypt</td>
-<td>40-128 / 5-16</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-odd"><td>CAST-256</td>
-<td>MCrypt</td>
-<td>128 / 16, 192 / 24, 256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-even"><td>Loki97</td>
-<td>MCrypt</td>
-<td>128 / 16, 192 / 24, 256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-odd"><td>SaferPlus</td>
-<td>MCrypt</td>
-<td>128 / 16, 192 / 24, 256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-even"><td>Serpent</td>
-<td>MCrypt</td>
-<td>128 / 16, 192 / 24, 256 / 32</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-odd"><td>XTEA</td>
-<td>MCrypt</td>
-<td>128 / 16</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-even"><td>RC2</td>
-<td>MCrypt</td>
-<td>8-1024 / 1-128</td>
-<td>CBC, CTR, CFB, CFB8, OFB, OFB8, ECB</td>
-</tr>
-<tr class="row-odd"><td>RC2</td>
-<td>OpenSSL</td>
-<td>8-1024 / 1-128</td>
-<td>CBC, CFB, OFB, ECB</td>
-</tr>
-<tr class="row-even"><td>Camellia-128</td>
-<td>OpenSSL</td>
-<td>128 / 16</td>
-<td>CBC, CFB, CFB8, OFB, ECB</td>
-</tr>
-<tr class="row-odd"><td>Camellia-192</td>
-<td>OpenSSL</td>
-<td>192 / 24</td>
-<td>CBC, CFB, CFB8, OFB, ECB</td>
-</tr>
-<tr class="row-even"><td>Camellia-256</td>
-<td>OpenSSL</td>
-<td>256 / 32</td>
-<td>CBC, CFB, CFB8, OFB, ECB</td>
-</tr>
-<tr class="row-odd"><td>Seed</td>
-<td>OpenSSL</td>
-<td>128 / 16</td>
-<td>CBC, CFB, OFB, ECB</td>
-</tr>
-</tbody>
-</table>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">If you wish to use one of those ciphers, you’d have to pass
-its name in lower-case to the Encryption library.</p>
-</div>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">You’ve probably noticed that all AES cipers (and Rijndael-128)
-are also listed in the portable ciphers list. This is because
-drivers support different modes for these ciphers. Also, it is
-important to note that AES-128 and Rijndael-128 are actually
-the same cipher, but <strong>only</strong> when used with a 128-bit key.</p>
-</div>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">CAST-128 / CAST-5 is also listed in both the portable and
-driver-specific ciphers list. This is because OpenSSL’s
-implementation doesn’t appear to be working correctly with
-key sizes of 80 bits and lower.</p>
-</div>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">RC2 is listed as supported by both MCrypt and OpenSSL.
-However, both drivers implement them differently and they
-are not portable. It is probably worth noting that we only
-found one obscure source confirming that it is MCrypt that
-is not properly implementing it.</p>
-</div>
-</div>
-<div class="section" id="encryption-modes">
-<span id="id1"></span><h4><a class="toc-backref" href="#id9">Encryption modes</a><a class="headerlink" href="#encryption-modes" title="Permalink to this headline">¶</a></h4>
-<p>Different modes of encryption have different characteristics and serve
-for different purposes. Some are stronger than others, some are faster
-and some offer extra features.
-We are not going in depth into that here, we’ll leave that to the
-cryptography experts. The table below is to provide brief informational
-reference to our more experienced users. If you are a beginner, just
-stick to the CBC mode - it is widely accepted as strong and secure for
-general purposes.</p>
-<table border="1" class="docutils">
-<colgroup>
-<col width="6%" />
-<col width="9%" />
-<col width="9%" />
-<col width="76%" />
-</colgroup>
-<thead valign="bottom">
-<tr class="row-odd"><th class="head">Mode name</th>
-<th class="head">CodeIgniter name</th>
-<th class="head">Driver support</th>
-<th class="head">Additional info</th>
-</tr>
-</thead>
-<tbody valign="top">
-<tr class="row-even"><td>CBC</td>
-<td>cbc</td>
-<td>MCrypt, OpenSSL</td>
-<td>A safe default choice</td>
-</tr>
-<tr class="row-odd"><td>CTR</td>
-<td>ctr</td>
-<td>MCrypt, OpenSSL</td>
-<td>Considered as theoretically better than CBC, but not as widely available</td>
-</tr>
-<tr class="row-even"><td>CFB</td>
-<td>cfb</td>
-<td>MCrypt, OpenSSL</td>
-<td>N/A</td>
-</tr>
-<tr class="row-odd"><td>CFB8</td>
-<td>cfb8</td>
-<td>MCrypt, OpenSSL</td>
-<td>Same as CFB, but operates in 8-bit mode (not recommended).</td>
-</tr>
-<tr class="row-even"><td>OFB</td>
-<td>ofb</td>
-<td>MCrypt, OpenSSL</td>
-<td>N/A</td>
-</tr>
-<tr class="row-odd"><td>OFB8</td>
-<td>ofb8</td>
-<td>MCrypt</td>
-<td>Same as OFB, but operates in 8-bit mode (not recommended).</td>
-</tr>
-<tr class="row-even"><td>ECB</td>
-<td>ecb</td>
-<td>MCrypt, OpenSSL</td>
-<td>Ignores IV (not recommended).</td>
-</tr>
-<tr class="row-odd"><td>XTS</td>
-<td>xts</td>
-<td>OpenSSL</td>
-<td>Usually used for encrypting random access data such as RAM or hard-disk storage.</td>
-</tr>
-<tr class="row-even"><td>Stream</td>
-<td>stream</td>
-<td>MCrypt, OpenSSL</td>
-<td>This is not actually a mode, it just says that a stream cipher is being used. Required because of the general cipher+mode initialization process.</td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="section" id="message-length">
-<h3><a class="toc-backref" href="#id10">Message Length</a><a class="headerlink" href="#message-length" title="Permalink to this headline">¶</a></h3>
-<p>It’s probably important for you to know that an encrypted string is usually
-longer than the original, plain-text string (depending on the cipher).</p>
-<p>This is influenced by the cipher algorithm itself, the IV prepended to the
-cipher-text and the HMAC authentication message that is also prepended.
-Furthermore, the encrypted message is also Base64-encoded so that it is safe
-for storage and transmission, regardless of a possible character set in use.</p>
-<p>Keep this information in mind when selecting your data storage mechanism.
-Cookies, for example, can only hold 4K of information.</p>
-</div>
-<div class="section" id="configuring-the-library">
-<span id="configuration"></span><h3><a class="toc-backref" href="#id11">Configuring the library</a><a class="headerlink" href="#configuring-the-library" title="Permalink to this headline">¶</a></h3>
-<p>For usability, performance, but also historical reasons tied to our old
-<a class="reference internal" href="encrypt.html"><span class="doc">Encrypt Class</span></a>, the Encryption library is designed to
-use repeatedly the same driver, encryption cipher, mode and key.</p>
-<p>As noted in the “Default behavior” section above, this means using an
-auto-detected driver (OpenSSL has a higher priority), the AES-128 ciper
-in CBC mode, and your <code class="docutils literal"><span class="pre">$config['encryption_key']</span></code> value.</p>
-<p>If you wish to change that however, you need to use the <code class="docutils literal"><span class="pre">initialize()</span></code>
-method. It accepts an associative array of parameters, all of which are
-optional:</p>
-<table border="1" class="docutils">
-<colgroup>
-<col width="15%" />
-<col width="85%" />
-</colgroup>
-<thead valign="bottom">
-<tr class="row-odd"><th class="head">Option</th>
-<th class="head">Possible values</th>
-</tr>
-</thead>
-<tbody valign="top">
-<tr class="row-even"><td>driver</td>
-<td>‘mcrypt’, ‘openssl’</td>
-</tr>
-<tr class="row-odd"><td>cipher</td>
-<td>Cipher name (see <a class="reference internal" href="#ciphers-and-modes"><span class="std std-ref">Supported encryption ciphers and modes</span></a>)</td>
-</tr>
-<tr class="row-even"><td>mode</td>
-<td>Encryption mode (see <a class="reference internal" href="#encryption-modes"><span class="std std-ref">Encryption modes</span></a>)</td>
-</tr>
-<tr class="row-odd"><td>key</td>
-<td>Encryption key</td>
-</tr>
-</tbody>
-</table>
-<p>For example, if you were to change the encryption algorithm and
-mode to AES-256 in CTR mode, this is what you should do:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span>
- <span class="k">array</span><span class="p">(</span>
- <span class="s1">&#39;cipher&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;aes-256&#39;</span><span class="p">,</span>
- <span class="s1">&#39;mode&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;ctr&#39;</span><span class="p">,</span>
- <span class="s1">&#39;key&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;&lt;a 32-character random string&gt;&#39;</span>
- <span class="p">)</span>
-<span class="p">);</span>
-</pre></div>
-</div>
-<p>Note that we only mentioned that you want to change the ciper and mode,
-but we also included a key in the example. As previously noted, it is
-important that you choose a key with a proper size for the used algorithm.</p>
-<p>There’s also the ability to change the driver, if for some reason you
-have both, but want to use MCrypt instead of OpenSSL:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Switch to the MCrypt driver</span>
-<span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span><span class="k">array</span><span class="p">(</span><span class="s1">&#39;driver&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;mcrypt&#39;</span><span class="p">));</span>
-
-<span class="c1">// Switch back to the OpenSSL driver</span>
-<span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span><span class="k">array</span><span class="p">(</span><span class="s1">&#39;driver&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;openssl&#39;</span><span class="p">));</span>
-</pre></div>
-</div>
-</div>
-<div class="section" id="encrypting-and-decrypting-data">
-<h3><a class="toc-backref" href="#id12">Encrypting and decrypting data</a><a class="headerlink" href="#encrypting-and-decrypting-data" title="Permalink to this headline">¶</a></h3>
-<p>Encrypting and decrypting data with the already configured library
-settings is simple. As simple as just passing the string to the
-<code class="docutils literal"><span class="pre">encrypt()</span></code> and/or <code class="docutils literal"><span class="pre">decrypt()</span></code> methods:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$plain_text</span> <span class="o">=</span> <span class="s1">&#39;This is a plain-text message!&#39;</span><span class="p">;</span>
-<span class="nv">$ciphertext</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">encrypt</span><span class="p">(</span><span class="nv">$plain_text</span><span class="p">);</span>
-
-<span class="c1">// Outputs: This is a plain-text message!</span>
-<span class="k">echo</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">decrypt</span><span class="p">(</span><span class="nv">$ciphertext</span><span class="p">);</span>
-</pre></div>
-</div>
-<p>And that’s it! The Encryption library will do everything necessary
-for the whole process to be cryptographically secure out-of-the-box.
-You don’t need to worry about it.</p>
-<div class="admonition important">
-<p class="first admonition-title">Important</p>
-<p class="last">Both methods will return FALSE in case of an error.
-While for <code class="docutils literal"><span class="pre">encrypt()</span></code> this can only mean incorrect
-configuration, you should always check the return value
-of <code class="docutils literal"><span class="pre">decrypt()</span></code> in production code.</p>
-</div>
-<div class="section" id="how-it-works">
-<h4><a class="toc-backref" href="#id13">How it works</a><a class="headerlink" href="#how-it-works" title="Permalink to this headline">¶</a></h4>
-<p>If you must know how the process works, here’s what happens under
-the hood:</p>
-<ul class="simple">
-<li><code class="docutils literal"><span class="pre">$this-&gt;encryption-&gt;encrypt($plain_text)</span></code><ol class="arabic">
-<li>Derive an encryption key and a HMAC key from your configured
-<em>encryption_key</em> via HKDF, using the SHA-512 digest algorithm.</li>
-<li>Generate a random initialization vector (IV).</li>
-<li>Encrypt the data via AES-128 in CBC mode (or another previously
-configured cipher and mode), using the above-mentioned derived
-encryption key and IV.</li>
-<li>Prepend said IV to the resulting cipher-text.</li>
-<li>Base64-encode the resulting string, so that it can be safely
-stored or transferred without worrying about character sets.</li>
-<li>Create a SHA-512 HMAC authentication message using the derived
-HMAC key to ensure data integrity and prepend it to the Base64
-string.</li>
-</ol>
-</li>
-<li><code class="docutils literal"><span class="pre">$this-&gt;encryption-&gt;decrypt($ciphertext)</span></code><ol class="arabic">
-<li>Derive an encryption key and a HMAC key from your configured
-<em>encryption_key</em> via HKDF, using the SHA-512 digest algorithm.
-Because your configured <em>encryption_key</em> is the same, this
-will produce the same result as in the <code class="docutils literal"><span class="pre">encrypt()</span></code> method
-above - otherwise you won’t be able to decrypt it.</li>
-<li>Check if the string is long enough, separate the HMAC out of
-it and validate if it is correct (this is done in a way that
-prevents timing attacks against it). Return FALSE if either of
-the checks fails.</li>
-<li>Base64-decode the string.</li>
-<li>Separate the IV out of the cipher-text and decrypt the said
-cipher-text using that IV and the derived encryption key.</li>
-</ol>
-</li>
-</ul>
-</div>
-<div class="section" id="using-custom-parameters">
-<span id="custom-parameters"></span><h4><a class="toc-backref" href="#id14">Using custom parameters</a><a class="headerlink" href="#using-custom-parameters" title="Permalink to this headline">¶</a></h4>
-<p>Let’s say you have to interact with another system that is out
-of your control and uses another method to encrypt data. A
-method that will most certainly not match the above-described
-sequence and probably not use all of the steps either.</p>
-<p>The Encryption library allows you to change how its encryption
-and decryption processes work, so that you can easily tailor a
-custom solution for such situations.</p>
-<div class="admonition note">
-<p class="first admonition-title">Note</p>
-<p class="last">It is possible to use the library in this way, without
-setting an <em>encryption_key</em> in your configuration file.</p>
-</div>
-<p>All you have to do is to pass an associative array with a few
-parameters to either the <code class="docutils literal"><span class="pre">encrypt()</span></code> or <code class="docutils literal"><span class="pre">decrypt()</span></code> method.
-Here’s an example:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Assume that we have $ciphertext, $key and $hmac_key</span>
-<span class="c1">// from on outside source</span>
-
-<span class="nv">$message</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">decrypt</span><span class="p">(</span>
- <span class="nv">$ciphertext</span><span class="p">,</span>
- <span class="k">array</span><span class="p">(</span>
- <span class="s1">&#39;cipher&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;blowfish&#39;</span><span class="p">,</span>
- <span class="s1">&#39;mode&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;cbc&#39;</span><span class="p">,</span>
- <span class="s1">&#39;key&#39;</span> <span class="o">=&gt;</span> <span class="nv">$key</span><span class="p">,</span>
- <span class="s1">&#39;hmac_digest&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;sha256&#39;</span><span class="p">,</span>
- <span class="s1">&#39;hmac_key&#39;</span> <span class="o">=&gt;</span> <span class="nv">$hmac_key</span>
- <span class="p">)</span>
-<span class="p">);</span>
-</pre></div>
-</div>
-<p>In the above example, we are decrypting a message that was encrypted
-using the Blowfish cipher in CBC mode and authenticated via a SHA-256
-HMAC.</p>
-<div class="admonition important">
-<p class="first admonition-title">Important</p>
-<p class="last">Note that both ‘key’ and ‘hmac_key’ are used in this
-example. When using custom parameters, encryption and HMAC keys
-are not derived like the default behavior of the library is.</p>
-</div>
-<p>Below is a list of the available options.</p>
-<p>However, unless you really need to and you know what you are doing,
-we advise you to not change the encryption process as this could
-impact security, so please do so with caution.</p>
-<table border="1" class="docutils">
-<colgroup>
-<col width="12%" />
-<col width="14%" />
-<col width="26%" />
-<col width="49%" />
-</colgroup>
-<thead valign="bottom">
-<tr class="row-odd"><th class="head">Option</th>
-<th class="head">Default value</th>
-<th class="head">Mandatory / Optional</th>
-<th class="head">Description</th>
-</tr>
-</thead>
-<tbody valign="top">
-<tr class="row-even"><td>cipher</td>
-<td>N/A</td>
-<td>Yes</td>
-<td>Encryption algorithm (see <a class="reference internal" href="#ciphers-and-modes"><span class="std std-ref">Supported encryption ciphers and modes</span></a>).</td>
-</tr>
-<tr class="row-odd"><td>mode</td>
-<td>N/A</td>
-<td>Yes</td>
-<td>Encryption mode (see <a class="reference internal" href="#encryption-modes"><span class="std std-ref">Encryption modes</span></a>).</td>
-</tr>
-<tr class="row-even"><td>key</td>
-<td>N/A</td>
-<td>Yes</td>
-<td>Encryption key.</td>
-</tr>
-<tr class="row-odd"><td>hmac</td>
-<td>TRUE</td>
-<td>No</td>
-<td>Whether to use a HMAC.
-Boolean. If set to FALSE, then <em>hmac_digest</em> and
-<em>hmac_key</em> will be ignored.</td>
-</tr>
-<tr class="row-even"><td>hmac_digest</td>
-<td>sha512</td>
-<td>No</td>
-<td>HMAC message digest algorithm (see <a class="reference internal" href="#digests"><span class="std std-ref">Supported HMAC authentication algorithms</span></a>).</td>
-</tr>
-<tr class="row-odd"><td>hmac_key</td>
-<td>N/A</td>
-<td>Yes, unless <em>hmac</em> is FALSE</td>
-<td>HMAC key.</td>
-</tr>
-<tr class="row-even"><td>raw_data</td>
-<td>FALSE</td>
-<td>No</td>
-<td>Whether the cipher-text should be raw.
-Boolean. If set to TRUE, then Base64 encoding and
-decoding will not be performed and HMAC will not
-be a hexadecimal string.</td>
-</tr>
-</tbody>
-</table>
-<div class="admonition important">
-<p class="first admonition-title">Important</p>
-<p class="last"><code class="docutils literal"><span class="pre">encrypt()</span></code> and <code class="docutils literal"><span class="pre">decrypt()</span></code> will return FALSE if
-a mandatory parameter is not provided or if a provided
-value is incorrect. This includes <em>hmac_key</em>, unless <em>hmac</em>
-is set to FALSE.</p>
-</div>
-</div>
-<div class="section" id="supported-hmac-authentication-algorithms">
-<span id="digests"></span><h4><a class="toc-backref" href="#id15">Supported HMAC authentication algorithms</a><a class="headerlink" href="#supported-hmac-authentication-algorithms" title="Permalink to this headline">¶</a></h4>
-<p>For HMAC message authentication, the Encryption library supports
-usage of the SHA-2 family of algorithms:</p>
-<table border="1" class="docutils">
-<colgroup>
-<col width="19%" />
-<col width="34%" />
-<col width="47%" />
-</colgroup>
-<thead valign="bottom">
-<tr class="row-odd"><th class="head">Algorithm</th>
-<th class="head">Raw length (bytes)</th>
-<th class="head">Hex-encoded length (bytes)</th>
-</tr>
-</thead>
-<tbody valign="top">
-<tr class="row-even"><td>sha512</td>
-<td>64</td>
-<td>128</td>
-</tr>
-<tr class="row-odd"><td>sha384</td>
-<td>48</td>
-<td>96</td>
-</tr>
-<tr class="row-even"><td>sha256</td>
-<td>32</td>
-<td>64</td>
-</tr>
-<tr class="row-odd"><td>sha224</td>
-<td>28</td>
-<td>56</td>
-</tr>
-</tbody>
-</table>
-<p>The reason for not including other popular algorithms, such as
-MD5 or SHA1 is that they are no longer considered secure enough
-and as such, we don’t want to encourage their usage.
-If you absolutely need to use them, it is easy to do so via PHP’s
-native <a class="reference external" href="http://php.net/manual/en/function.hash-hmac.php">hash_hmac()</a> function.</p>
-<p>Stronger algorithms of course will be added in the future as they
-appear and become widely available.</p>
-</div>
-</div>
-</div>
-<div class="section" id="class-reference">
-<h2><a class="toc-backref" href="#id16">Class Reference</a><a class="headerlink" href="#class-reference" title="Permalink to this headline">¶</a></h2>
-<dl class="class">
-<dt id="CI_Encryption">
-<em class="property">class </em><code class="descname">CI_Encryption</code><a class="headerlink" href="#CI_Encryption" title="Permalink to this definition">¶</a></dt>
-<dd><dl class="method">
-<dt id="CI_Encryption::initialize">
-<code class="descname">initialize</code><span class="sig-paren">(</span><em>$params</em><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::initialize" title="Permalink to this definition">¶</a></dt>
-<dd><table class="docutils field-list" frame="void" rules="none">
-<col class="field-name" />
-<col class="field-body" />
-<tbody valign="top">
-<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
-<li><strong>$params</strong> (<em>array</em>) – Configuration parameters</li>
-</ul>
-</td>
-</tr>
-<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">CI_Encryption instance (method chaining)</p>
-</td>
-</tr>
-<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">CI_Encryption</p>
-</td>
-</tr>
-</tbody>
-</table>
-<p>Initializes (configures) the library to use a different
-driver, cipher, mode or key.</p>
-<p>Example:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">initialize</span><span class="p">(</span>
- <span class="k">array</span><span class="p">(</span><span class="s1">&#39;mode&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;ctr&#39;</span><span class="p">)</span>
-<span class="p">);</span>
-</pre></div>
-</div>
-<p>Please refer to the <a class="reference internal" href="#configuration"><span class="std std-ref">Configuring the library</span></a> section for detailed info.</p>
-</dd></dl>
-
-<dl class="method">
-<dt id="CI_Encryption::encrypt">
-<code class="descname">encrypt</code><span class="sig-paren">(</span><em>$data</em><span class="optional">[</span>, <em>$params = NULL</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::encrypt" title="Permalink to this definition">¶</a></dt>
-<dd><table class="docutils field-list" frame="void" rules="none">
-<col class="field-name" />
-<col class="field-body" />
-<tbody valign="top">
-<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
-<li><strong>$data</strong> (<em>string</em>) – Data to encrypt</li>
-<li><strong>$params</strong> (<em>array</em>) – Optional parameters</li>
-</ul>
-</td>
-</tr>
-<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">Encrypted data or FALSE on failure</p>
-</td>
-</tr>
-<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
-</td>
-</tr>
-</tbody>
-</table>
-<p>Encrypts the input data and returns its ciphertext.</p>
-<p>Example:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$ciphertext</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">encrypt</span><span class="p">(</span><span class="s1">&#39;My secret message&#39;</span><span class="p">);</span>
-</pre></div>
-</div>
-<p>Please refer to the <a class="reference internal" href="#custom-parameters"><span class="std std-ref">Using custom parameters</span></a> section for information
-on the optional parameters.</p>
-</dd></dl>
-
-<dl class="method">
-<dt id="CI_Encryption::decrypt">
-<code class="descname">decrypt</code><span class="sig-paren">(</span><em>$data</em><span class="optional">[</span>, <em>$params = NULL</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::decrypt" title="Permalink to this definition">¶</a></dt>
-<dd><table class="docutils field-list" frame="void" rules="none">
-<col class="field-name" />
-<col class="field-body" />
-<tbody valign="top">
-<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
-<li><strong>$data</strong> (<em>string</em>) – Data to decrypt</li>
-<li><strong>$params</strong> (<em>array</em>) – Optional parameters</li>
-</ul>
-</td>
-</tr>
-<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">Decrypted data or FALSE on failure</p>
-</td>
-</tr>
-<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
-</td>
-</tr>
-</tbody>
-</table>
-<p>Decrypts the input data and returns it in plain-text.</p>
-<p>Example:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="k">echo</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">decrypt</span><span class="p">(</span><span class="nv">$ciphertext</span><span class="p">);</span>
-</pre></div>
-</div>
-<p>Please refer to the <a class="reference internal" href="#custom-parameters"><span class="std std-ref">Using custom parameters</span></a> secrion for information
-on the optional parameters.</p>
-</dd></dl>
-
-<dl class="method">
-<dt id="CI_Encryption::create_key">
-<code class="descname">create_key</code><span class="sig-paren">(</span><em>$length</em><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::create_key" title="Permalink to this definition">¶</a></dt>
-<dd><table class="docutils field-list" frame="void" rules="none">
-<col class="field-name" />
-<col class="field-body" />
-<tbody valign="top">
-<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
-<li><strong>$length</strong> (<em>int</em>) – Output length</li>
-</ul>
-</td>
-</tr>
-<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">A pseudo-random cryptographic key with the specified length, or FALSE on failure</p>
-</td>
-</tr>
-<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
-</td>
-</tr>
-</tbody>
-</table>
-<p>Creates a cryptographic key by fetching random data from
-the operating system’s sources (i.e. /dev/urandom).</p>
-</dd></dl>
-
-<dl class="method">
-<dt id="CI_Encryption::hkdf">
-<code class="descname">hkdf</code><span class="sig-paren">(</span><em>$key</em><span class="optional">[</span>, <em>$digest = 'sha512'</em><span class="optional">[</span>, <em>$salt = NULL</em><span class="optional">[</span>, <em>$length = NULL</em><span class="optional">[</span>, <em>$info = ''</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Encryption::hkdf" title="Permalink to this definition">¶</a></dt>
-<dd><table class="docutils field-list" frame="void" rules="none">
-<col class="field-name" />
-<col class="field-body" />
-<tbody valign="top">
-<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
-<li><strong>$key</strong> (<em>string</em>) – Input key material</li>
-<li><strong>$digest</strong> (<em>string</em>) – A SHA-2 family digest algorithm</li>
-<li><strong>$salt</strong> (<em>string</em>) – Optional salt</li>
-<li><strong>$length</strong> (<em>int</em>) – Optional output length</li>
-<li><strong>$info</strong> (<em>string</em>) – Optional context/application-specific info</li>
-</ul>
-</td>
-</tr>
-<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">A pseudo-random key or FALSE on failure</p>
-</td>
-</tr>
-<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">string</p>
-</td>
-</tr>
-</tbody>
-</table>
-<p>Derives a key from another, presumably weaker key.</p>
-<p>This method is used internally to derive an encryption and HMAC key
-from your configured <em>encryption_key</em>.</p>
-<p>It is publicly available due to its otherwise general purpose. It is
-described in <a class="reference external" href="https://tools.ietf.org/rfc/rfc5869.txt">RFC 5869</a>.</p>
-<p>However, as opposed to the description in RFC 5869, this implementation
-doesn’t support SHA1.</p>
-<p>Example:</p>
-<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$hmac_key</span> <span class="o">=</span> <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">encryption</span><span class="o">-&gt;</span><span class="na">hkdf</span><span class="p">(</span>
- <span class="nv">$key</span><span class="p">,</span>
- <span class="s1">&#39;sha512&#39;</span><span class="p">,</span>
- <span class="k">NULL</span><span class="p">,</span>
- <span class="k">NULL</span><span class="p">,</span>
- <span class="s1">&#39;authentication&#39;</span>
-<span class="p">);</span>
-
-<span class="c1">// $hmac_key is a pseudo-random key with a length of 64 bytes</span>
-</pre></div>
-</div>
-</dd></dl>
-
-</dd></dl>
-
-</div>
-</div>
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