code: private void readTrustStore() throws IOException, FormatNotUnderstoodException {
  		if (((this.hocr.getSigTruststoreFile() != null) && (!"".equals(this.hocr.getSigTruststoreFile())))) {
  			LOG.info("Reading truststore to validate certificate chain for signatures");
  			FlinkKeyStoreManager fksm = new FlinkKeyStoreManager();
  			try {
  				fksm.openKeyStore(new Path(this.hocr.getSigTruststoreFile()), this.hocr.getSigTruststoreType(),
  						this.hocr.getSigTruststorePassword());
  				this.hocr.setX509CertificateChain(fksm.getAllX509Certificates());
  			} catch (NoSuchAlgorithmException | CertificateException | KeyStoreException | IllegalArgumentException e) {
  				LOG.error("Exception: ",e);
  				throw new FormatNotUnderstoodException(
  						"Cannot read truststore to establish certificate chain for signature validation " + e);
  			}
  
  		}
  	}
docs: *
  Read truststore for establishing certificate chain for signature validation
  
  @param conf
  @throws IOException
  @throws FormatNotUnderstoodException