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<title>Encrypting data.</title>
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<br clear="all"><div class="SECT1">
<h1 class="SECT1"><a name="XMLSEC-NOTES-ENCRYPT">Encrypting data.</a></h1>
<p>The typical encryption process includes following steps:
</p>
<p></p>
<ul>
<li><p> Prepare data for encryption.
</p></li>
<li><p> Create or load encryption template and select start
<enc:EncryptedData/> node.
</p></li>
<li><p> Create encryption context <a href="xmlsec-xmlenc.html#XMLSECENCCTX">xmlSecEncCtx</a>
using <a href="xmlsec-xmlenc.html#XMLSECENCCTXCREATE">xmlSecEncCtxCreate</a> or
<a href="xmlsec-xmlenc.html#XMLSECENCCTXINITIALIZE">xmlSecEncCtxInitialize</a>
functions.
</p></li>
<li><p> Load encryption key in <a href="xmlsec-keysmngr.html#XMLSECKEYSMNGR">keys manager</a>
or generate a session key and set it in the encryption context
(<code class="STRUCTFIELD">encKey</code> member of
<a href="xmlsec-xmlenc.html#XMLSECENCCTX">xmlSecEncCtx</a> structure).
</p></li>
<li>
<p> Encrypt data by calling one of the following functions:
</p>
<p></p>
<ul>
<li><p> <a href="xmlsec-xmlenc.html#XMLSECENCCTXBINARYENCRYPT">xmlSecEncCtxBinaryEncrypt</a>
</p></li>
<li><p> <a href="xmlsec-xmlenc.html#XMLSECENCCTXXMLENCRYPT">xmlSecEncCtxXmlEncrypt</a>
</p></li>
<li><p> <a href="xmlsec-xmlenc.html#XMLSECENCCTXURIENCRYPT">xmlSecEncCtxUriEncrypt</a>
</p></li>
</ul>
</li>
<li><p> Check returned value and if necessary consume encrypted data.
</p></li>
<li><p> Destroy encryption context <a href="xmlsec-xmlenc.html#XMLSECENCCTX">xmlSecEncCtx</a>
using <a href="xmlsec-xmlenc.html#XMLSECENCCTXDESTROY">xmlSecEncCtxDestroy</a> or
<a href="xmlsec-xmlenc.html#XMLSECENCCTXFINALIZE">xmlSecEncCtxFinalize</a>
functions.
</p></li>
</ul>
<p> </p>
<div class="EXAMPLE">
<a name="AEN227"></a><p><b>Example 2. Encrypting binary data with a template.</b></p>
<pre class="PROGRAMLISTING">/**
* encrypt_file:
* @tmpl_file: the encryption template file name.
* @key_file: the Triple DES key file.
* @data: the binary data to encrypt.
* @dataSize: the binary data size.
*
* Encrypts binary #data using template from #tmpl_file and DES key from
* #key_file.
*
* Returns 0 on success or a negative value if an error occurs.
*/
int
encrypt_file(const char* tmpl_file, const char* key_file, const unsigned char* data, size_t dataSize) {
xmlDocPtr doc = NULL;
xmlNodePtr node = NULL;
xmlSecEncCtxPtr encCtx = NULL;
int res = -1;
assert(tmpl_file);
assert(key_file);
assert(data);
/* load template */
doc = xmlParseFile(tmpl_file);
if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
fprintf(stderr, "Error: unable to parse file \"%s\"\n", tmpl_file);
goto done;
}
/* find start node */
node = xmlSecFindNode(xmlDocGetRootElement(doc), xmlSecNodeEncryptedData, xmlSecEncNs);
if(node == NULL) {
fprintf(stderr, "Error: start node not found in \"%s\"\n", tmpl_file);
goto done;
}
/* create encryption context, we don't need keys manager in this example */
encCtx = xmlSecEncCtxCreate(NULL);
if(encCtx == NULL) {
fprintf(stderr,"Error: failed to create encryption context\n");
goto done;
}
/* load DES key */
encCtx->encKey = xmlSecKeyReadBinaryFile(xmlSecKeyDataDesId, key_file);
if(encCtx->encKey == NULL) {
fprintf(stderr,"Error: failed to load des key from binary file \"%s\"\n", key_file);
goto done;
}
/* set key name to the file name, this is just an example! */
if(xmlSecKeySetName(encCtx->encKey, key_file) < 0) {
fprintf(stderr,"Error: failed to set key name for key from \"%s\"\n", key_file);
goto done;
}
/* encrypt the data */
if(xmlSecEncCtxBinaryEncrypt(encCtx, node, data, dataSize) < 0) {
fprintf(stderr,"Error: encryption failed\n");
goto done;
}
/* print encrypted data with document to stdout */
xmlDocDump(stdout, doc);
/* success */
res = 0;
done:
/* cleanup */
if(encCtx != NULL) {
xmlSecEncCtxDestroy(encCtx);
}
if(doc != NULL) {
xmlFreeDoc(doc);
}
return(res);
}
</pre>
<p><a href="xmlsec-encrypt-template-file.html#XMLSEC-EXAMPLE-ENCRYPT1">Full program listing</a></p>
<p><a href="xmlsec-encrypt-template-file.html#XMLSEC-EXAMPLE-ENCRYPT1-TMPL">Simple encryption template file</a></p>
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