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<title>Generates a PKCS5 v2 PBKDF2 string</title>
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<h1 class="refname">openssl_pbkdf2</h1>
<p class="verinfo">(PHP 5 >= 5.5.0, PHP 7)</p><p class="refpurpose"><span class="refname">openssl_pbkdf2</span> — <span class="dc-title">Generates a PKCS5 v2 PBKDF2 string</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.openssl-pbkdf2-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">string</span> <span class="methodname"><strong>openssl_pbkdf2</strong></span>
( <span class="methodparam"><span class="type">string</span> <code class="parameter">$password</code></span>
, <span class="methodparam"><span class="type">string</span> <code class="parameter">$salt</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$key_length</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$iterations</code></span>
[, <span class="methodparam"><span class="type">string</span> <code class="parameter">$digest_algorithm</code><span class="initializer"> = "sha1"</span></span>
] )</div>
<p class="para rdfs-comment">
<span class="function"><strong>openssl_pbkdf2()</strong></span> computes PBKDF2 (Password-Based Key Derivation Function 2),
a key derivation function defined in PKCS5 v2.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.openssl-pbkdf2-parameters">
<h3 class="title">Parameters</h3>
<dl>
<dt>
<code class="parameter">password</code></dt>
<dd>
<p class="para">
Password from which the derived key is generated.
</p>
</dd>
<dt>
<code class="parameter">salt</code></dt>
<dd>
<p class="para">
PBKDF2 recommends a crytographic salt of at least 64 bits (8 bytes).
</p>
</dd>
<dt>
<code class="parameter">key_length</code></dt>
<dd>
<p class="para">
Length of desired output key.
</p>
</dd>
<dt>
<code class="parameter">iterations</code></dt>
<dd>
<p class="para">
The number of iterations desired. <a href="https://pages.nist.gov/800-63-3/sp800-63b.html#sec5" class="link external">» NIST
recommends at least 10,000</a>.
</p>
</dd>
<dt>
<code class="parameter">digest_algorithm</code></dt>
<dd>
<p class="para">
Optional hash or digest algorithm from <span class="function"><a href="function.openssl-get-md-methods.html" class="function">openssl_get_md_methods()</a></span>. Defaults to SHA-1.
</p>
</dd>
</dl>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.openssl-pbkdf2-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns raw binary string or <strong><code>FALSE</code></strong> on failure.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.openssl-pbkdf2-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-973">
<p><strong>Example #1 openssl_pbkdf2() example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$password </span><span style="color: #007700">= </span><span style="color: #DD0000">'yOuR-pAs5w0rd-hERe'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$salt </span><span style="color: #007700">= </span><span style="color: #0000BB">openssl_random_pseudo_bytes</span><span style="color: #007700">(</span><span style="color: #0000BB">12</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$keyLength </span><span style="color: #007700">= </span><span style="color: #0000BB">40</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$iterations </span><span style="color: #007700">= </span><span style="color: #0000BB">10000</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$generated_key </span><span style="color: #007700">= </span><span style="color: #0000BB">openssl_pbkdf2</span><span style="color: #007700">(</span><span style="color: #0000BB">$password</span><span style="color: #007700">, </span><span style="color: #0000BB">$salt</span><span style="color: #007700">, </span><span style="color: #0000BB">$keyLength</span><span style="color: #007700">, </span><span style="color: #0000BB">$iterations</span><span style="color: #007700">, </span><span style="color: #DD0000">'sha256'</span><span style="color: #007700">);<br />echo </span><span style="color: #0000BB">bin2hex</span><span style="color: #007700">(</span><span style="color: #0000BB">$generated_key</span><span style="color: #007700">).</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br />echo </span><span style="color: #0000BB">base64_encode</span><span style="color: #007700">(</span><span style="color: #0000BB">$generated_key</span><span style="color: #007700">).</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.openssl-pbkdf2-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><span class="function"><a href="function.hash-pbkdf2.html" class="function" rel="rdfs-seeAlso">hash_pbkdf2()</a> - Generate a PBKDF2 key derivation of a supplied password</span></li>
<li class="member"><span class="function"><a href="function.openssl-get-md-methods.html" class="function" rel="rdfs-seeAlso">openssl_get_md_methods()</a> - Gets available digest methods</span></li>
</ul>
</p>
</div>
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