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<title>Cryptographic transforms.</title>
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<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>
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