<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/> <meta http-equiv="X-UA-Compatible" content="IE=9"/> <meta name="generator" content="Doxygen 1.8.14"/> <meta name="viewport" content="width=device-width, initial-scale=1"/> <title>Crypto++: gf256.cpp Source File</title> <link href="tabs.css" rel="stylesheet" type="text/css"/> <script type="text/javascript" src="jquery.js"></script> <script type="text/javascript" src="dynsections.js"></script> <link href="doxygen.css" rel="stylesheet" type="text/css" /> </head> <body> <div id="top"><!-- do not remove this div, it is closed by doxygen! --> <div id="titlearea"> <table cellspacing="0" cellpadding="0"> <tbody> <tr style="height: 56px;"> <td id="projectalign" style="padding-left: 0.5em;"> <div id="projectname">Crypto++  <span id="projectnumber">7.0</span> </div> <div id="projectbrief">Free C++ class library of cryptographic schemes</div> </td> </tr> </tbody> </table> </div> <!-- end header part --> <!-- Generated by Doxygen 1.8.14 --> <script type="text/javascript" src="menudata.js"></script> <script type="text/javascript" src="menu.js"></script> <script type="text/javascript"> /* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&dn=gpl-2.0.txt GPL-v2 */ $(function() { initMenu('',false,false,'search.php','Search'); }); /* @license-end */</script> <div id="main-nav"></div> </div><!-- top --> <div class="header"> <div class="headertitle"> <div class="title">gf256.cpp</div> </div> </div><!--header--> <div class="contents"> <div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">// gf256.cpp - originally written and placed in the public domain by Wei Dai</span></div><div class="line"><a name="l00002"></a><span class="lineno"> 2</span> </div><div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="preprocessor">#include "<a class="code" href="pch_8h.html">pch.h</a>"</span></div><div class="line"><a name="l00004"></a><span class="lineno"> 4</span> <span class="preprocessor">#include "<a class="code" href="gf256_8h.html">gf256.h</a>"</span></div><div class="line"><a name="l00005"></a><span class="lineno"> 5</span> </div><div class="line"><a name="l00006"></a><span class="lineno"> 6</span> NAMESPACE_BEGIN(<a class="code" href="namespace_crypto_p_p.html">CryptoPP</a>)</div><div class="line"><a name="l00007"></a><span class="lineno"> 7</span> </div><div class="line"><a name="l00008"></a><span class="lineno"> 8</span> GF256::Element GF256::Multiply(Element a, Element b)<span class="keyword"> const</span></div><div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="keyword"></span>{</div><div class="line"><a name="l00010"></a><span class="lineno"> 10</span>  word result = 0, t = b;</div><div class="line"><a name="l00011"></a><span class="lineno"> 11</span> </div><div class="line"><a name="l00012"></a><span class="lineno"> 12</span>  <span class="keywordflow">for</span> (<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> i=0; i<8; i++)</div><div class="line"><a name="l00013"></a><span class="lineno"> 13</span>  {</div><div class="line"><a name="l00014"></a><span class="lineno"> 14</span>  result <<= 1;</div><div class="line"><a name="l00015"></a><span class="lineno"> 15</span>  <span class="keywordflow">if</span> (result & 0x100)</div><div class="line"><a name="l00016"></a><span class="lineno"> 16</span>  result ^= m_modulus;</div><div class="line"><a name="l00017"></a><span class="lineno"> 17</span> </div><div class="line"><a name="l00018"></a><span class="lineno"> 18</span>  t <<= 1;</div><div class="line"><a name="l00019"></a><span class="lineno"> 19</span>  <span class="keywordflow">if</span> (t & 0x100)</div><div class="line"><a name="l00020"></a><span class="lineno"> 20</span>  result ^= a;</div><div class="line"><a name="l00021"></a><span class="lineno"> 21</span>  }</div><div class="line"><a name="l00022"></a><span class="lineno"> 22</span> </div><div class="line"><a name="l00023"></a><span class="lineno"> 23</span>  <span class="keywordflow">return</span> (GF256::Element) result;</div><div class="line"><a name="l00024"></a><span class="lineno"> 24</span> }</div><div class="line"><a name="l00025"></a><span class="lineno"> 25</span> </div><div class="line"><a name="l00026"></a><span class="lineno"> 26</span> GF256::Element GF256::MultiplicativeInverse(Element a)<span class="keyword"> const</span></div><div class="line"><a name="l00027"></a><span class="lineno"> 27</span> <span class="keyword"></span>{</div><div class="line"><a name="l00028"></a><span class="lineno"> 28</span>  Element result = a;</div><div class="line"><a name="l00029"></a><span class="lineno"> 29</span>  <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i=1; i<7; i++)</div><div class="line"><a name="l00030"></a><span class="lineno"> 30</span>  result = Multiply(<a class="code" href="class_square.html">Square</a>(result), a);</div><div class="line"><a name="l00031"></a><span class="lineno"> 31</span>  <span class="keywordflow">return</span> <a class="code" href="class_square.html">Square</a>(result);</div><div class="line"><a name="l00032"></a><span class="lineno"> 32</span> }</div><div class="line"><a name="l00033"></a><span class="lineno"> 33</span> </div><div class="line"><a name="l00034"></a><span class="lineno"> 34</span> NAMESPACE_END</div><div class="ttc" id="class_square_html"><div class="ttname"><a href="class_square.html">Square</a></div><div class="ttdoc">Square block cipher. </div><div class="ttdef"><b>Definition:</b> <a href="square_8h_source.html#l00024">square.h:24</a></div></div> <div class="ttc" id="pch_8h_html"><div class="ttname"><a href="pch_8h.html">pch.h</a></div><div class="ttdoc">Precompiled header file. </div></div> <div class="ttc" id="gf256_8h_html"><div class="ttname"><a href="gf256_8h.html">gf256.h</a></div><div class="ttdoc">Classes and functions for schemes over GF(256) </div></div> <div class="ttc" id="namespace_crypto_p_p_html"><div class="ttname"><a href="namespace_crypto_p_p.html">CryptoPP</a></div><div class="ttdoc">Crypto++ library namespace. </div></div> </div><!-- fragment --></div><!-- contents --> <!-- start footer part --> <hr class="footer"/><address class="footer"><small> Generated on Sun Sep 16 2018 07:57:52 for Crypto++ by  <a href="http://www.doxygen.org/index.html"> <img class="footer" src="doxygen.png" alt="doxygen"/> </a> 1.8.14 </small></address> </body> </html>