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<title>RAND_set_rand_method</title>
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<ul id="index">
  <li><a href="#NAME">NAME</a></li>
  <li><a href="#SYNOPSIS">SYNOPSIS</a></li>
  <li><a href="#DESCRIPTION">DESCRIPTION</a></li>
  <li><a href="#THE-RAND_METHOD-STRUCTURE">THE RAND_METHOD STRUCTURE</a></li>
  <li><a href="#RETURN-VALUES">RETURN VALUES</a></li>
  <li><a href="#SEE-ALSO">SEE ALSO</a></li>
  <li><a href="#COPYRIGHT">COPYRIGHT</a></li>
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<p>RAND_set_rand_method, RAND_get_rand_method, RAND_OpenSSL - select RAND method</p>

<h1 id="SYNOPSIS">SYNOPSIS</h1>

<pre><code> #include &lt;openssl/rand.h&gt;

RAND_METHOD *RAND_OpenSSL(void);

int RAND_set_rand_method(const RAND_METHOD *meth);

const RAND_METHOD *RAND_get_rand_method(void);</code></pre>

<h1 id="DESCRIPTION">DESCRIPTION</h1>

<p>A <b>RAND_METHOD</b> specifies the functions that OpenSSL uses for random number generation.</p>

<p>RAND_OpenSSL() returns the default <b>RAND_METHOD</b> implementation by OpenSSL. This implementation ensures that the PRNG state is unique for each thread.</p>

<p>If an <b>ENGINE</b> is loaded that provides the RAND API, however, it will be used instead of the method returned by RAND_OpenSSL().</p>

<p>RAND_set_rand_method() makes <b>meth</b> the method for PRNG use. If an ENGINE was providing the method, it will be released first.</p>

<p>RAND_get_rand_method() returns a pointer to the current <b>RAND_METHOD</b>.</p>

<h1 id="THE-RAND_METHOD-STRUCTURE">THE RAND_METHOD STRUCTURE</h1>

<pre><code> typedef struct rand_meth_st {
     int (*seed)(const void *buf, int num);
     int (*bytes)(unsigned char *buf, int num);
     void (*cleanup)(void);
     int (*add)(const void *buf, int num, double entropy);
     int (*pseudorand)(unsigned char *buf, int num);
     int (*status)(void);
 } RAND_METHOD;</code></pre>

<p>The fields point to functions that are used by, in order, RAND_seed(), RAND_bytes(), internal RAND cleanup, RAND_add(), RAND_pseudo_rand() and RAND_status(). Each pointer may be NULL if the function is not implemented.</p>

<h1 id="RETURN-VALUES">RETURN VALUES</h1>

<p>RAND_set_rand_method() returns 1 on success and 0 on failure. RAND_get_rand_method() and RAND_OpenSSL() return pointers to the respective methods.</p>

<p><a href="../man3/RAND_bytes.html">RAND_bytes(3)</a>, <a href="../man3/ENGINE_by_id.html">ENGINE_by_id(3)</a>, <a href="../man7/RAND.html">RAND(7)</a></p>

<h1 id="COPYRIGHT">COPYRIGHT</h1>

<p>Licensed under the OpenSSL license (the &quot;License&quot;). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>

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