e sophisticated 
     */
    mngr = xmlSecKeysMngrCreate();
    if(mngr == NULL) {
	fprintf(stderr, "Error: failed to create keys manager.\n");
	return(NULL);
    }
    if(xmlSecCryptoAppDefaultKeysMngrInit(mngr) &lt; 0) {
	fprintf(stderr, "Error: failed to initialize keys manager.\n");
	xmlSecKeysMngrDestroy(mngr);
	return(NULL);
    }    
    
    /* load private RSA key */
    key = xmlSecCryptoAppKeyLoad(key_file, xmlSecKeyDataFormatPem, NULL, NULL, NULL);
    if(key == NULL) {
        fprintf(stderr,"E