<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Cryptographic transforms.</title> <meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.79"> <link rel="HOME" title="XML Security Library Reference Manual" href="index.html"> <link rel="UP" title="Adding support for new cryptographic library." href="xmlsec-notes-new-crypto.html"> <link rel="PREVIOUS" title="Klasses and objects." href="xmlsec-notes-new-crypto-klasses.html"> <link rel="NEXT" title="Keys data and keys data stores." href="xmlsec-notes-new-crypto-keys.html"> <style type="text/css">.synopsis, .classsynopsis { background: #eeeeee; border: solid 1px #aaaaaa; padding: 0.5em; } .programlisting { background: #eeeeff; border: solid 1px #aaaaff; padding: 0.5em; } .variablelist { padding: 4px; margin-left: 3em; } .navigation { background: #ffeeee; border: solid 1px #ffaaaa; margin-top: 0.5em; margin-bottom: 0.5em; } .navigation a { color: #770000; } .navigation a:visited { color: #550000; } .navigation .title { font-size: 200%; }</style> </head> <body><table witdh="100%" valign="top"><tr valign="top"> <td valign="top" align="left" width="210"> <img src="../images/logo.gif" alt="XML Security Library" border="0"><p></p> <ul> <li><a href="../index.html">Home</a></li> <li><a href="../download.html">Download</a></li> <li><a href="../news.html">News</a></li> <li><a href="../documentation.html">Documentation</a></li> <ul> <li><a href="../faq.html">FAQ</a></li> <li><a href="../api/xmlsec-notes.html">Tutorial</a></li> <li><a href="../api/xmlsec-reference.html">API reference</a></li> <li><a href="../api/xmlsec-examples.html">Examples</a></li> </ul> <li><a href="../xmldsig.html">XML Digital Signature</a></li> <ul><li><a href="http://www.aleksey.com/xmlsec/xmldsig-verifier.html">Online Verifier</a></li></ul> <li><a href="../xmlenc.html">XML Encryption</a></li> <li><a href="../c14n.html">XML Canonicalization</a></li> <li><a href="../bugs.html">Reporting Bugs</a></li> <li><a href="http://www.aleksey.com/pipermail/xmlsec">Mailing list</a></li> <li><a href="../related.html">Related</a></li> <li><a href="../authors.html">Authors</a></li> </ul> <table width="100%"> <tr> <td width="15"></td> <td><a href="http://xmlsoft.org/"><img src="../images/libxml2-logo.png" alt="LibXML2" border="0"></a></td> </tr> <tr> <td width="15"></td> <td><a href="http://xmlsoft.org/XSLT"><img src="../images/libxslt-logo.png" alt="LibXSLT" border="0"></a></td> </tr> <tr> <td width="15"></td> <td><a href="http://www.openssl.org/"><img src="../images/openssl-logo.png" alt="OpenSSL" border="0"></a></td> </tr> <!--Links - start--><!--Links - end--> </table> </td> <td valign="top"><table width="100%" valign="top"><tr><td valign="top" align="left" id="xmlsecContent"> <table width="100%" class="navigation" summary="Navigation header" cellpadding="2" cellspacing="2"><tr valign="middle"> <td><a accesskey="p" href="xmlsec-notes-new-crypto-klasses.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td> <td><a accesskey="u" href="xmlsec-notes-new-crypto.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td> <td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td> <th width="100%" align="center">XML Security Library Reference Manual</th> <td><a accesskey="n" href="xmlsec-notes-new-crypto-keys.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td> </tr></table> <br clear="all"><div class="SECT1"> <h1 class="SECT1"><a name="XMLSEC-NOTES-NEW-CRYPTO-TRANSFORMS">Cryptographic transforms.</a></h1> <p>The cryptographic transforms (digests, signatures and encryption) implementation is the main goal of "xmlsec-<crypto>" library. Most of the cryptographic <a href="xmlsec-notes-transforms.html">transforms</a> use default <code class="STRUCTFIELD">pushBin</code> and <code class="STRUCTFIELD">popBin</code> methods and provide custom <a href="xmlsec-transforms.html#XMLSECTRANSFORMEXECUTEMETHOD">execute</a> method. The binary transform <a href="xmlsec-transforms.html#XMLSECTRANSFORMEXECUTEMETHOD">execute</a> method processes data from the input buffer <code class="STRUCTFIELD">inBuf</code> and pushes results to <code class="STRUCTFIELD">outBuf</code>. The transform should try to consume and remove data from <code class="STRUCTFIELD">inBuf</code> buffer as soon as the data became available. However, it might happen that current data size in the input buffer is not enough (for example, RSA-PKCS1 algorithm requires that all the data are available in one buffer). In this case, transform might keep the data in the input buffer till the next call to <a href="xmlsec-transforms.html#XMLSECTRANSFORMEXECUTEMETHOD">execute</a> method. The "last" parameter of the <a href="xmlsec-transforms.html#XMLSECTRANSFORMEXECUTEMETHOD">execute</a> indicates that transform MUST process all the data in the input buffer and return as much as possible in the output buffer. The <a href="xmlsec-transforms.html#XMLSECTRANSFORMEXECUTEMETHOD">execute</a> method might be called multiple times with non-zero "last" parameter until the transforms returns nothing in the output buffer. In addition, the transform implementation is responsible for managing the transform <code class="STRUCTFIELD">status</code> variable. </p> <div class="TABLE"> <a name="AEN590"></a><p><b>Table 2. Typical transform status managing.</b></p> <table border="1" class="CALSTABLE"> <col> <col> <tbody> <tr> <td>xmlSecTransformStatusNone</td> <td>Transform initializes itself (for example, cipher transform generates or reads IV) and sets <code class="STRUCTFIELD">status</code> variable to xmlSecTransformStatusWorking.</td> </tr> <tr> <td>xmlSecTransformStatusWorking</td> <td>Transform process the next (if "last" parameter is zero) or last block of data (if "last" parameter is non-zero). When transform returns all the data, it sets the <code class="STRUCTFIELD">status</code> variable to xmlSecTransformStatusFinished.</td> </tr> <tr> <td>xmlSecTransformStatusFinished</td> <td>Transform returns no data to indicate that it finished processing.</td> </tr> </tbody> </table> </div> <p>In adition to <a href="xmlsec-transforms.html#XMLSECTRANSFORMEXECUTEMETHOD">execute</a> methods, signature, hmac or digest transforms MUST implement <a href="xmlsec-transforms.html#XMLSECTRANSFORMVERIFYMETHOD">verify</a> method. The <a href="xmlsec-transforms.html#XMLSECTRANSFORMVERIFYMETHOD">verify</a> method is called after transform execution is finished. The <a href="xmlsec-transforms.html#XMLSECTRANSFORMVERIFYMETHOD">verify</a> method implementation must set the "status" member to <a href="xmlsec-transforms.html#XMLSECTRANSFORMSTATUSOK">xmlSecTransformStatusOk</a> if signature, hmac or digest is successfuly verified or to <a href="xmlsec-transforms.html#XMLSECTRANSFORMSTATUSFAIL">xmlSecTransformStatusFail</a> otherwise. </p> <p>The transforms that require a key (signature or encryption transforms, for example) MUST imlpement <a href="xmlsec-transforms.html#XMLSECTRANSFORMSETKEYREQUIREMENTSMETHOD">setKeyReq</a> (prepares the <a href="xmlsec-keys.html#XMLSECKEYREQ">key requirements</a> for key search) and <a href="xmlsec-transforms.html#XMLSECTRANSFORMSETKEYMETHOD">setKey</a> (sets the key in the transform) methods. </p> </div> <table class="navigation" width="100%" summary="Navigation footer" cellpadding="2" cellspacing="2"><tr valign="middle"> <td align="left"><a accesskey="p" href="xmlsec-notes-new-crypto-klasses.html"><b><<< Klasses and objects.</b></a></td> <td align="right"><a accesskey="n" href="xmlsec-notes-new-crypto-keys.html"><b>Keys data and keys data stores. >>></b></a></td> </tr></table> </td></tr></table></td> </tr></table></body> </html>