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<ul>
<li><a href="#name">NAME</a></li>
<li><a href="#synopsis">SYNOPSIS</a></li>
<li><a href="#description">DESCRIPTION</a></li>
<li><a href="#return_values">RETURN VALUES</a></li>
<li><a href="#notes">NOTES</a></li>
<li><a href="#see_also">SEE ALSO</a></li>
<li><a href="#history">HISTORY</a></li>
<li><a href="#copyright">COPYRIGHT</a></li>
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<p>
</p>
<hr />
<h1><a name="name">NAME</a></h1>
<p>RAND_DRBG_new,
RAND_DRBG_secure_new,
RAND_DRBG_set,
RAND_DRBG_set_defaults,
RAND_DRBG_instantiate,
RAND_DRBG_uninstantiate,
RAND_DRBG_free
- initialize and cleanup a RAND_DRBG instance</p>
<p>
</p>
<hr />
<h1><a name="synopsis">SYNOPSIS</a></h1>
<pre>
#include <openssl/rand_drbg.h></pre>
<pre>
RAND_DRBG *RAND_DRBG_new(int type,
unsigned int flags,
RAND_DRBG *parent);</pre>
<pre>
RAND_DRBG *RAND_DRBG_secure_new(int type,
unsigned int flags,
RAND_DRBG *parent);</pre>
<pre>
int RAND_DRBG_set(RAND_DRBG *drbg,
int type, unsigned int flags);</pre>
<pre>
int RAND_DRBG_set_defaults(int type, unsigned int flags);</pre>
<pre>
int RAND_DRBG_instantiate(RAND_DRBG *drbg,
const unsigned char *pers, size_t perslen);</pre>
<pre>
int RAND_DRBG_uninstantiate(RAND_DRBG *drbg);</pre>
<pre>
void RAND_DRBG_free(RAND_DRBG *drbg);</pre>
<p>
</p>
<hr />
<h1><a name="description">DESCRIPTION</a></h1>
<p><code>RAND_DRBG_new()</code> and <code>RAND_DRBG_secure_new()</code>
create a new DRBG instance of the given <strong>type</strong>, allocated from the heap resp.
the secure heap
(using <code>OPENSSL_zalloc()</code> resp. OPENSSL_secure_zalloc()).</p>
<p><code>RAND_DRBG_set()</code> initializes the <strong>drbg</strong> with the given <strong>type</strong> and <strong>flags</strong>.</p>
<p><code>RAND_DRBG_set_defaults()</code> sets the default <strong>type</strong> and <strong>flags</strong> for new DRBG
instances.</p>
<p>Currently, all DRBG types are based on AES-CTR, so <strong>type</strong> can be one of the
following values: NID_aes_128_ctr, NID_aes_192_ctr, NID_aes_256_ctr.
Before the DRBG can be used to generate random bits, it is necessary to set
its type and to instantiate it.</p>
<p>The optional <strong>flags</strong> argument specifies a set of bit flags which can be
joined using the | operator. Currently, the only flag is
RAND_DRBG_FLAG_CTR_NO_DF, which disables the use of the derivation function
ctr_df. For an explanation, see [NIST SP 800-90A Rev. 1].</p>
<p>If a <strong>parent</strong> instance is specified then this will be used instead of
the default entropy source for reseeding the <strong>drbg</strong>. It is said that the
<strong>drbg</strong> is <em>chained</em> to its <strong>parent</strong>.
For more information, see the NOTES section.</p>
<p><code>RAND_DRBG_instantiate()</code>
seeds the <strong>drbg</strong> instance using random input from trusted entropy sources.
Optionally, a personalization string <strong>pers</strong> of length <strong>perslen</strong> can be
specified.
To omit the personalization string, set <strong>pers</strong>=NULL and <strong>perslen</strong>=0;</p>
<p><code>RAND_DRBG_uninstantiate()</code>
clears the internal state of the <strong>drbg</strong> and puts it back in the
uninstantiated state.</p>
<p>
</p>
<hr />
<h1><a name="return_values">RETURN VALUES</a></h1>
<p><code>RAND_DRBG_new()</code> and <code>RAND_DRBG_secure_new()</code> return a pointer to a DRBG
instance allocated on the heap, resp. secure heap.</p>
<p><code>RAND_DRBG_set()</code>,
<code>RAND_DRBG_instantiate()</code>, and
<code>RAND_DRBG_uninstantiate()</code>
return 1 on success, and 0 on failure.</p>
<p><code>RAND_DRBG_free()</code> does not return a value.</p>
<p>
</p>
<hr />
<h1><a name="notes">NOTES</a></h1>
<p>The DRBG design supports <em>chaining</em>, which means that a DRBG instance can
use another <strong>parent</strong> DRBG instance instead of the default entropy source
to obtain fresh random input for reseeding, provided that <strong>parent</strong> DRBG
instance was properly instantiated, either from a trusted entropy source,
or from yet another parent DRBG instance.
For a detailed description of the reseeding process, see <em>RAND_DRBG(7)</em>.</p>
<p>The default DRBG type and flags are applied only during creation of a DRBG
instance.
To ensure that they are applied to the global and thread-local DRBG instances
(<master>, resp. <public> and <private>), it is necessary to call
<code>RAND_DRBG_set_defaults()</code> before creating any thread and before calling any
cryptographic routines that obtain random data directly or indirectly.</p>
<p>
</p>
<hr />
<h1><a name="see_also">SEE ALSO</a></h1>
<p><em>OPENSSL_zalloc(3)</em>,
<em>OPENSSL_secure_zalloc(3)</em>,
<em>RAND_DRBG_generate(3)</em>,
<em>RAND_DRBG(7)</em></p>
<p>
</p>
<hr />
<h1><a name="history">HISTORY</a></h1>
<p>The RAND_DRBG functions were added in OpenSSL 1.1.1.</p>
<p>
</p>
<hr />
<h1><a name="copyright">COPYRIGHT</a></h1>
<p>Copyright 2017-2020 The OpenSSL Project Authors. All Rights Reserved.</p>
<p>Licensed under the OpenSSL license (the "License"). 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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