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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_reseed,
RAND_DRBG_set_reseed_interval,
RAND_DRBG_set_reseed_time_interval,
RAND_DRBG_set_reseed_defaults
- reseed a RAND_DRBG instance</p>
<p>
</p>
<hr />
<h1><a name="synopsis">SYNOPSIS</a></h1>
<pre>
#include <openssl/rand_drbg.h></pre>
<pre>
int RAND_DRBG_reseed(RAND_DRBG *drbg,
const unsigned char *adin, size_t adinlen,
int prediction_resistance);</pre>
<pre>
int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg,
unsigned int interval);</pre>
<pre>
int RAND_DRBG_set_reseed_time_interval(RAND_DRBG *drbg,
time_t interval);</pre>
<pre>
int RAND_DRBG_set_reseed_defaults(
unsigned int master_reseed_interval,
unsigned int slave_reseed_interval,
time_t master_reseed_time_interval,
time_t slave_reseed_time_interval
);</pre>
<p>
</p>
<hr />
<h1><a name="description">DESCRIPTION</a></h1>
<p><code>RAND_DRBG_reseed()</code>
reseeds the given <strong>drbg</strong>, obtaining entropy input from its entropy source
and mixing in the specified additional data provided in the buffer <strong>adin</strong>
of length <strong>adinlen</strong>.
The additional data can be omitted by setting <strong>adin</strong> to NULL and <strong>adinlen</strong>
to 0.
An immediate reseeding from a live entropy source can be requested by setting
the <strong>prediction_resistance</strong> flag to 1.
This feature is not implemented yet, so reseeding with prediction resistance
requested will always fail.</p>
<p><code>RAND_DRBG_set_reseed_interval()</code>
sets the reseed interval of the <strong>drbg</strong>, which is the maximum allowed number
of generate requests between consecutive reseedings.
If <strong>interval</strong> > 0, then the <strong>drbg</strong> will reseed automatically whenever the
number of generate requests since its last seeding exceeds the given reseed
interval.
If <strong>interval</strong> == 0, then this feature is disabled.</p>
<p><code>RAND_DRBG_set_reseed_time_interval()</code>
sets the reseed time interval of the <strong>drbg</strong>, which is the maximum allowed
number of seconds between consecutive reseedings.
If <strong>interval</strong> > 0, then the <strong>drbg</strong> will reseed automatically whenever the
elapsed time since its last reseeding exceeds the given reseed time interval.
If <strong>interval</strong> == 0, then this feature is disabled.</p>
<p><code>RAND_DRBG_set_reseed_defaults()</code> sets the default values for the reseed interval
(<strong>master_reseed_interval</strong> and <strong>slave_reseed_interval</strong>)
and the reseed time interval
(<strong>master_reseed_time_interval</strong> and <strong>slave_reseed_tme_interval</strong>)
of DRBG instances.
The default values are set independently for master DRBG instances (which don't
have a parent) and slave DRBG instances (which are chained to a parent DRBG).</p>
<p>
</p>
<hr />
<h1><a name="return_values">RETURN VALUES</a></h1>
<p><code>RAND_DRBG_reseed()</code>,
<code>RAND_DRBG_set_reseed_interval()</code>, and
<code>RAND_DRBG_set_reseed_time_interval()</code>,
return 1 on success, 0 on failure.</p>
<p>
</p>
<hr />
<h1><a name="notes">NOTES</a></h1>
<p>The default OpenSSL random generator is already set up for automatic reseeding,
so in general it is not necessary to reseed it explicitly, or to modify
its reseeding thresholds.</p>
<p>Normally, the entropy input for seeding a DRBG is either obtained from a
trusted os entropy source or from a parent DRBG instance, which was seeded
(directly or indirectly) from a trusted os entropy source.
In exceptional cases it is possible to replace the reseeding mechanism entirely
by providing application defined callbacks using <code>RAND_DRBG_set_callbacks()</code>.</p>
<p>The reseeding default values 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_reseed_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>RAND_DRBG_generate(3)</em>,
<em>RAND_DRBG_bytes(3)</em>,
<em>RAND_DRBG_set_callbacks(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 2017-2019 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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