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<title>GnuTLS 3.5.4: Random number generation</title>
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<a name="Random-number-generation"></a>
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<p>
Next: <a href="Overriding-algorithms.html#Overriding-algorithms" accesskey="n" rel="next">Overriding algorithms</a>, Previous: <a href="Hash-and-MAC-functions.html#Hash-and-MAC-functions" accesskey="p" rel="prev">Hash and MAC functions</a>, Up: <a href="Using-GnuTLS-as-a-cryptographic-library.html#Using-GnuTLS-as-a-cryptographic-library" accesskey="u" rel="up">Using GnuTLS as a cryptographic library</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Function-and-Data-Index.html#Function-and-Data-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Random-number-generation-1"></a>
<h3 class="section">8.4 Random number generation</h3>
<a name="index-random-numbers"></a>
<p>Access to the random number generator is provided using the <a href="Cryptographic-API.html#gnutls_005frnd">gnutls_rnd</a>
function. It allows obtaining random data of various levels.
</p>
<div class="float"><a name="gnutls_005frnd_005flevel_005ft"></a>
<dl compact="compact">
<dt><code>GNUTLS_RND_NONCE</code></dt>
<dd><p>Non-predictable random number. Fatal in parts
of session if broken, i.e., vulnerable to statistical analysis.
</p></dd>
<dt><code>GNUTLS_RND_RANDOM</code></dt>
<dd><p>Pseudo-random cryptographic random number.
Fatal in session if broken.
</p></dd>
<dt><code>GNUTLS_RND_KEY</code></dt>
<dd><p>Fatal in many sessions if broken.
</p></dd>
</dl>
<div class="float-caption"><p><strong>Figure 8.5: </strong>The random number levels.</p></div></div>
<dl>
<dt><a name="index-gnutls_005frnd"></a>Function: <em>int</em> <strong>gnutls_rnd</strong> <em>(gnutls_rnd_level_t <var>level</var>, void * <var>data</var>, size_t <var>len</var>)</em></dt>
<dd><p><var>level</var>: a security level
</p>
<p><var>data</var>: place to store random bytes
</p>
<p><var>len</var>: The requested size
</p>
<p>This function will generate random data and store it to output
buffer.
</p>
<p>This function is thread-safe and also fork-safe.
</p>
<p><strong>Returns:</strong> Zero on success, or a negative error code on error.
</p>
<p><strong>Since:</strong> 2.12.0
</p></dd></dl>
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