php-doc-en/reference/hash/functions/hash-pbkdf2.xml

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<refentry xml:id="function.hash-pbkdf2" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>hash_pbkdf2</refname>
  <refpurpose>Generate a PBKDF2 key derivation of a supplied password</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis role="procedural">
   <type>string</type><methodname>hash_pbkdf2</methodname>
   <methodparam><type>string</type><parameter>algo</parameter></methodparam>
   <methodparam><type>string</type><parameter>password</parameter></methodparam>
   <methodparam><type>string</type><parameter>salt</parameter></methodparam>
   <methodparam><type>int</type><parameter>iterations</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>length</parameter><initializer>0</initializer></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter>raw_output</parameter><initializer>false</initializer></methodparam>
  </methodsynopsis>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>algo</parameter></term>
     <listitem>
      <para>
       Name of selected hashing algorithm (i.e. <literal>md5</literal>,
       <literal>sha256</literal>, <literal>haval160,4</literal>, etc..) See
       <function>hash_algos</function> for a list of supported algorithms.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>password</parameter></term>
     <listitem>
      <para>
       The password to use for the derivation.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>salt</parameter></term>
     <listitem>
      <para>
       The salt to use for the derivation. This value should be generated randomly.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>iterations</parameter></term>
     <listitem>
      <para>
       The number of internal iterations to perform for the derivation.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>length</parameter></term>
     <listitem>
      <para>
       The length of the output string. If <parameter>raw_output</parameter>
       is &true; this corresponds to the byte-length of the derived key, if
       <parameter>raw_output</parameter> is &false; this corresponds to twice the
       byte-length of the derived key (as every byte of the key is returned as
       two hexits).
      </para>
      <para>
       If <literal>0</literal> is passed, the entire output of the supplied
       algorithm is used.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>raw_output</parameter></term>
     <listitem>
      <para>
       When set to &true;, outputs raw binary data. &false; outputs lowercase
       hexits.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues"><!-- {{{ -->
  &reftitle.returnvalues;
  <para>
   Returns a string containing the derived key as lowercase hexits unless
   <parameter>raw_output</parameter> is set to &true; in which case the raw
   binary representation of the derived key is returned.
  </para>
 </refsect1><!-- }}} -->

 <refsect1 role="errors"><!-- {{{ -->
  &reftitle.errors;
  <para>
   An <constant>E_WARNING</constant> will be raised if the algorithm is
   unknown, the <parameter>iterations</parameter> parameter is less than or
   equal to <literal>0</literal>, the <parameter>length</parameter> is less
   than <literal>0</literal> or the <parameter>salt</parameter> is too long
   (greater than <constant>INT_MAX</constant><literal> - 4</literal>).
  </para>
 </refsect1><!-- }}} -->

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>hash_pbkdf2</function> example, basic usage</title>
    <programlisting role="php">
<![CDATA[
<?php
$password = "password";
$iterations = 1000;

// Generate a random IV using mcrypt_create_iv(),
// openssl_random_pseudo_bytes() or another suitable source of randomness
$salt = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM);

$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 20);
echo $hash;
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
120fb6cffcf8b32c43e7
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <caution>
   <para>
    The PBKDF2 method can be used for hashing passwords for storage. However, it
    should be noted that <function>password_hash</function> or
    <function>crypt</function> with <constant>CRYPT_BLOWFISH</constant> are
    better suited for password storage.
   </para>
  </caution>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>crypt</function></member>
    <member><function>password_hash</function></member>
    <member><function>hash</function></member>
    <member><function>hash_algos</function></member>
    <member><function>hash_init</function></member>
    <member><function>hash_hmac</function></member>
    <member><function>hash_hmac_file</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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