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The typical encryption process includes following steps:
Prepare data for encryption.
Create or load encryption template and select start <enc:EncryptedData/> node.
Create encryption context xmlSecEncCtx using xmlSecEncCtxCreate or xmlSecEncCtxInitialize functions.
Load encryption key in keys manager
or generate a session key and set it in the encryption context
(encKey member of
xmlSecEncCtx structure).
Encrypt data by calling one of the following functions:
Check returned value and if necessary consume encrypted data.
Destroy encryption context xmlSecEncCtx using xmlSecEncCtxDestroy or xmlSecEncCtxFinalize functions.
Example 11. Encrypting binary data with a template.
/**
* 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);
}