125 lines
4.6 KiB
HTML
Executable File
125 lines
4.6 KiB
HTML
Executable File
<?xml version="1.0" ?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>RAND_DRBG_generate</title>
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<meta http-equiv="content-type" content="text/html; charset=utf-8" />
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<link rev="made" href="mailto:root@localhost" />
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</head>
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<body style="background-color: white">
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<!-- INDEX BEGIN -->
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<div name="index">
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<p><a name="__index__"></a></p>
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<ul>
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<li><a href="#name">NAME</a></li>
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<li><a href="#synopsis">SYNOPSIS</a></li>
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<li><a href="#description">DESCRIPTION</a></li>
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<li><a href="#return_values">RETURN VALUES</a></li>
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<li><a href="#notes">NOTES</a></li>
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<li><a href="#see_also">SEE ALSO</a></li>
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<li><a href="#history">HISTORY</a></li>
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<li><a href="#copyright">COPYRIGHT</a></li>
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</ul>
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<hr name="index" />
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</div>
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<!-- INDEX END -->
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<p>
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</p>
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<hr />
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<h1><a name="name">NAME</a></h1>
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<p>RAND_DRBG_generate,
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RAND_DRBG_bytes
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- generate random bytes using the given drbg instance</p>
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<p>
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</p>
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<hr />
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<h1><a name="synopsis">SYNOPSIS</a></h1>
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<pre>
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#include <openssl/rand_drbg.h></pre>
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<pre>
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int RAND_DRBG_generate(RAND_DRBG *drbg,
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unsigned char *out, size_t outlen,
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int prediction_resistance,
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const unsigned char *adin, size_t adinlen);</pre>
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<pre>
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int RAND_DRBG_bytes(RAND_DRBG *drbg,
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unsigned char *out, size_t outlen);</pre>
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<p>
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</p>
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<hr />
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<h1><a name="description">DESCRIPTION</a></h1>
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<p><code>RAND_DRBG_generate()</code> generates <strong>outlen</strong> random bytes using the given
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DRBG instance <strong>drbg</strong> and stores them in the buffer at <strong>out</strong>.</p>
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<p>Before generating the output, the DRBG instance checks whether the maximum
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number of generate requests (<em>reseed interval</em>) or the maximum timespan
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(<em>reseed time interval</em>) since its last seeding have been reached.
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If this is the case, the DRBG reseeds automatically.
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Additionally, an immediate reseeding can be requested by setting the
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<strong>prediction_resistance</strong> flag to 1.
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Requesting prediction resistance is a relative expensive operation.
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See NOTES section for more details.</p>
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<p>The caller can optionally provide additional data to be used for reseeding
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by passing a pointer <strong>adin</strong> to a buffer of length <strong>adinlen</strong>.
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This additional data is mixed into the internal state of the random
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generator but does not contribute to the entropy count.
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The additional data can be omitted by setting <strong>adin</strong> to NULL and
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<strong>adinlen</strong> to 0;</p>
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<p><code>RAND_DRBG_bytes()</code> generates <strong>outlen</strong> random bytes using the given
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DRBG instance <strong>drbg</strong> and stores them in the buffer at <strong>out</strong>.
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This function is a wrapper around the <code>RAND_DRBG_generate()</code> call,
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which collects some additional data from low entropy sources
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(e.g., a high resolution timer) and calls
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RAND_DRBG_generate(drbg, out, outlen, 0, adin, adinlen).</p>
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<p>
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</p>
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<hr />
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<h1><a name="return_values">RETURN VALUES</a></h1>
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<p><code>RAND_DRBG_generate()</code> and <code>RAND_DRBG_bytes()</code> return 1 on success,
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and 0 on failure.</p>
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<p>
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</p>
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<hr />
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<h1><a name="notes">NOTES</a></h1>
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<p>The <em>reseed interval</em> and <em>reseed time interval</em> of the <strong>drbg</strong> are set to
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reasonable default values, which in general do not have to be adjusted.
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If necessary, they can be changed using <em>RAND_DRBG_set_reseed_interval(3)</em>
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and <em>RAND_DRBG_set_reseed_time_interval(3)</em>, respectively.</p>
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<p>A request for prediction resistance can only be satisfied by pulling fresh
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entropy from a live entropy source (section 5.5.2 of [NIST SP 800-90C]).
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It is up to the user to ensure that a live entropy source is configured
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and is being used.</p>
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<p>
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</p>
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<hr />
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<h1><a name="see_also">SEE ALSO</a></h1>
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<p><em>RAND_bytes(3)</em>,
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<em>RAND_DRBG_set_reseed_interval(3)</em>,
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<em>RAND_DRBG_set_reseed_time_interval(3)</em>,
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<em>RAND_DRBG(7)</em></p>
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<p>
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</p>
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<hr />
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<h1><a name="history">HISTORY</a></h1>
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<p>The RAND_DRBG functions were added in OpenSSL 1.1.1.</p>
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<p>Prediction resistance is supported from OpenSSL 3.0.</p>
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<p>
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</p>
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<hr />
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<h1><a name="copyright">COPYRIGHT</a></h1>
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<p>Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.</p>
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<p>Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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<a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>
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</body>
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</html>
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