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<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="xmlsec-notes-dynamic-encryption-templates"></a>Creating dynamic encryption templates.</h2></div></div></div>
<p>The encryption template has structure similar 
	to the XML Encryption structure as it is described in 
	<a class="ulink" href="" target="_top">specification</a>.
	The only difference is that some nodes (for example,
	&lt;enc:CipherValue/&gt;)
	are empty. The XML Security Library sets the content of these
	nodes after doing necessary calculations.
	</p>
<div class="figure">
<a name="id-1.2.7.4.3"></a><p class="title"><b>Figure 4. XML Encryption structure</b></p>
<div class="figure-contents"><pre class="programlisting">
&lt;enc:EncryptedData Id? Type? MimeType? Encoding?&gt;
    &lt;enc:EncryptionMethod Algorithm /&gt;?
    (&lt;dsig:KeyInfo&gt;
	&lt;dsig:KeyName&gt;?
	&lt;dsig:KeyValue&gt;?
	&lt;dsig:RetrievalMethod&gt;?
	&lt;dsig:X509Data&gt;?
	&lt;dsig:PGPData&gt;?
	&lt;enc:EncryptedKey&gt;?
	&lt;enc:AgreementMethod&gt;?
	&lt;dsig:KeyName&gt;?
	&lt;dsig:RetrievalMethod&gt;?
	&lt;*&gt;?
    &lt;/dsig:KeyInfo&gt;)?
    &lt;enc:CipherData&gt;
	&lt;enc:CipherValue&gt;?
	&lt;enc:CipherReference URI?&gt;?
    &lt;/enc:CipherData&gt;
    &lt;enc:EncryptionProperties&gt;?
&lt;/enc:EncryptedData&gt;	
	    </pre></div>
</div>
<br class="figure-break"><p>
	     </p>
<div class="example">
<a name="id-1.2.7.4.4.1"></a><p class="title"><b>Example 13. Creating dynamic encrytion template.</b></p>
<div class="example-contents">
<pre class="programlisting">
/**
 * encrypt_file:
 * @xml_file:		the encryption template file name.
 * @key_file:		the Triple DES key file.
 *
 * Encrypts #xml_file using a dynamicaly created template and DES key from
 * #key_file.
 *
 * Returns 0 on success or a negative value if an error occurs.
 */
int 
encrypt_file(const char* xml_file, const char* key_file) {
    xmlDocPtr doc = NULL;
    xmlNodePtr encDataNode = NULL;
    xmlNodePtr keyInfoNode = NULL;
    xmlSecEncCtxPtr encCtx = NULL;
    int res = -1;
    
    assert(xml_file);
    assert(key_file);

    /* load template */
    doc = xmlParseFile(xml_file);
    if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
	fprintf(stderr, "Error: unable to parse file \"%s\"\n", xml_file);
	goto done;	
    }
    
    /* create encryption template to encrypt XML file and replace 
     * its content with encryption result */
    encDataNode = xmlSecTmplEncDataCreate(doc, xmlSecTransformDes3CbcId,
				NULL, xmlSecTypeEncElement, NULL, NULL);
    if(encDataNode == NULL) {
	fprintf(stderr, "Error: failed to create encryption template\n");
	goto done;   
    }

    /* we want to put encrypted data in the &lt;enc:CipherValue/&gt; node */
    if(xmlSecTmplEncDataEnsureCipherValue(encDataNode) == NULL) {
	fprintf(stderr, "Error: failed to add CipherValue node\n");
	goto done;   
    }

    /* add &lt;dsig:KeyInfo/&gt; and &lt;dsig:KeyName/&gt; nodes to put key name in the signed document */
    keyInfoNode = xmlSecTmplEncDataEnsureKeyInfo(encDataNode, NULL);
    if(keyInfoNode == NULL) {
	fprintf(stderr, "Error: failed to add key info\n");
	goto done;		
    }

    if(xmlSecTmplKeyInfoAddKeyName(keyInfoNode, NULL) == NULL) {
	fprintf(stderr, "Error: failed to add key name\n");
	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, assuming that there is not password */
    encCtx-&gt;encKey = xmlSecKeyReadBinaryFile(xmlSecKeyDataDesId, key_file);
    if(encCtx-&gt;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-&gt;encKey, key_file) &lt; 0) {
    	fprintf(stderr,"Error: failed to set key name for key from \"%s\"\n", key_file);
	goto done;
    }

    /* encrypt the data */
    if(xmlSecEncCtxXmlEncrypt(encCtx, encDataNode, xmlDocGetRootElement(doc)) &lt; 0) {
        fprintf(stderr,"Error: encryption failed\n");
	goto done;
    }
    
    /* we template is inserted in the doc */
    encDataNode = NULL;
        
    /* print encrypted data with document to stdout */
    xmlDocDump(stdout, doc);
    
    /* success */
    res = 0;

done:    

    /* cleanup */
    if(encCtx != NULL) {
	xmlSecEncCtxDestroy(encCtx);
    }

    if(encDataNode != NULL) {
	xmlFreeNode(encDataNode);
    }
        
    if(doc != NULL) {
	xmlFreeDoc(doc); 
    }
    return(res);
}
		</pre>
<p><a class="link" href="xmlsec-encrypt-dynamic-template.html#xmlsec-example-encrypt2" title="encrypt2.c">Full program listing</a></p>
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<p><br class="example-break">
	</p>
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