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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>3.2 rand -- An interface to the OpenSSL pseudo random number generator </title> <META NAME="description" CONTENT="3.2 rand -- An interface to the OpenSSL pseudo random number generator "> <META NAME="keywords" CONTENT="pyOpenSSL"> <META NAME="resource-type" CONTENT="document"> <META NAME="distribution" CONTENT="global"> <link rel="STYLESHEET" href="pyOpenSSL.css"> <LINK REL="next" href="openssl-ssl.html"> <LINK REL="previous" href="openssl-crypto.html"> <LINK REL="up" href="openssl.html"> <LINK REL="next" href="openssl-ssl.html"> </head> <body> <DIV CLASS="navigation"> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td><A href="openssl-netscape-spki.html"><img src="previous.gif" border="0" height="32" alt="Previous Page" width="32"></A></td> <td><A href="openssl.html"><img src="up.gif" border="0" height="32" alt="Up One Level" width="32"></A></td> <td><A href="openssl-ssl.html"><img src="next.gif" border="0" height="32" alt="Next Page" width="32"></A></td> <td align="center" width="100%">Python OpenSSL Manual</td> <td><A href="contents.html"><img src="contents.gif" border="0" height="32" alt="Contents" width="32"></A></td> <td><img src="blank.gif" border="0" height="32" alt="" width="32"></td> <td><img src="blank.gif" border="0" height="32" alt="" width="32"></td> </tr></table> <b class="navlabel">Previous:</b> <a class="sectref" href="openssl-netscape-spki.html">3.1.9 NetscapeSPKI objects</A> <b class="navlabel">Up:</b> <a class="sectref" href="openssl.html">3 OpenSSL </A> <b class="navlabel">Next:</b> <a class="sectref" href="openssl-ssl.html">3.3 SSL </A> <br><hr> </DIV> <!--End of Navigation Panel--> <H2><A NAME="SECTION000420000000000000000"> </A> <BR> 3.2 <tt class="module">rand</tt> -- An interface to the OpenSSL pseudo random number generator </H2> <P> <P> This module handles the OpenSSL pseudo random number generator (PRNG) and declares the following: <P> <dl><dt><b><a name='l2h-98'><tt class='function'>add</tt></a></b>(<var>string, entropy</var>) <dd> Mix bytes from <var>string</var> into the PRNG state. The <var>entropy</var> argument is (the lower bound of) an estimate of how much randomness is contained in <var>string</var>, measured in bytes. For more information, see e.g. <a class="rfc" name="rfcref-2096" href="http://www.ietf.org/rfc/rfc1750.txt">RFC 1750</a>. </dl> <P> <dl><dt><b><a name='l2h-99'><tt class='function'>bytes</tt></a></b>(<var>num_bytes</var>) <dd> Get some random bytes from the PRNG as a string. <P> This is a wrapper for the C function <tt class="function">RAND_bytes</tt>. </dl> <P> <dl><dt><b><a name='l2h-100'><tt class='function'>cleanup</tt></a></b>() <dd> Erase the memory used by the PRNG. <P> This is a wrapper for the C function <tt class="function">RAND_cleanup</tt>. </dl> <P> <dl><dt><b><a name='l2h-101'><tt class='function'>egd</tt></a></b>(<var>path</var><big>[</big><var>, bytes</var><big>]</big>) <dd> Query the Entropy Gathering Daemon<A NAME="tex2html2" HREF="#foot1108"><SUP>2</SUP></A> on socket <var>path</var> for <var>bytes</var> bytes of random data and and uses <tt class="function">add</tt> to seed the PRNG. The default value of <var>bytes</var> is 255. </dl> <P> <dl><dt><b><a name='l2h-102'><tt class='function'>load_file</tt></a></b>(<var>path</var><big>[</big><var>, bytes</var><big>]</big>) <dd> Read <var>bytes</var> bytes (or all of it, if <var>bytes</var> is negative) of data from the file <var>path</var> to seed the PRNG. The default value of <var>bytes</var> is -1. </dl> <P> <dl><dt><b><a name='l2h-103'><tt class='function'>screen</tt></a></b>() <dd> Add the current contents of the screen to the PRNG state. Availability: Windows. </dl> <P> <dl><dt><b><a name='l2h-104'><tt class='function'>seed</tt></a></b>(<var>string</var>) <dd> This is equivalent to calling <tt class="function">add</tt> with <var>entropy</var> as the length of the string. </dl> <P> <dl><dt><b><a name='l2h-105'><tt class='function'>status</tt></a></b>() <dd> Returns true if the PRNG has been seeded with enough data, and false otherwise. </dl> <P> <dl><dt><b><a name='l2h-106'><tt class='function'>write_file</tt></a></b>(<var>path</var>) <dd> Write a number of random bytes (currently 1024) to the file <var>path</var>. This file can then be used with <tt class="function">load_file</tt> to seed the PRNG again. </dl> <P> <dl><dt><b>exception <a name='l2h-107'><tt class='exception'>Error</tt></a></b> <dd> If the current RAND method supports any errors, this is raised when needed. The default method does not raise this when the entropy pool is depleted. <P> Whenever this exception is raised directly, it has a list of error messages from the OpenSSL error queue, where each item is a tuple <code>(<var>lib</var>, <var>function</var>, <var>reason</var>)</code>. Here <var>lib</var>, <var>function</var> and <var>reason</var> are all strings, describing where and what the problem is. See <span class='manpage'><i>err</i>(3)</span> for more information. </dl> <P> <BR><HR><H4>Footnotes</H4> <DL> <DT><A NAME="foot1108">... Daemon</A><A href="openssl-rand.html#tex2html2"><SUP>2</SUP></A></DT> <DD>See <a class="url" href="http://www.lothar.com/tech/crypto/">http://www.lothar.com/tech/crypto/</a> </DD> </DL> <DIV CLASS="navigation"> <p><hr> <table align="center" width="100%" cellpadding="0" cellspacing="2"> <tr> <td><A href="openssl-netscape-spki.html"><img src="previous.gif" border="0" height="32" alt="Previous Page" width="32"></A></td> <td><A href="openssl.html"><img src="up.gif" border="0" height="32" alt="Up One Level" width="32"></A></td> <td><A href="openssl-ssl.html"><img src="next.gif" border="0" height="32" alt="Next Page" width="32"></A></td> <td align="center" width="100%">Python OpenSSL Manual</td> <td><A href="contents.html"><img src="contents.gif" border="0" height="32" alt="Contents" width="32"></A></td> <td><img src="blank.gif" border="0" height="32" alt="" width="32"></td> <td><img src="blank.gif" border="0" height="32" alt="" width="32"></td> </tr></table> <b class="navlabel">Previous:</b> <a class="sectref" href="openssl-netscape-spki.html">3.1.9 NetscapeSPKI objects</A> <b class="navlabel">Up:</b> <a class="sectref" href="openssl.html">3 OpenSSL </A> <b class="navlabel">Next:</b> <a class="sectref" href="openssl-ssl.html">3.3 SSL </A> <hr> <span class="release-info">Release 0.10.</span> </DIV> <!--End of Navigation Panel--> </BODY> </HTML>