code: protected Collection<X509CertSelector> getSignerSelectors() {
  		X509CertSelector digSigSelector = new X509CertSelector();
  		digSigSelector.setBasicConstraints(-2);
  		digSigSelector.setKeyUsage(new boolean[] { true });
  
  		X509CertSelector caSelector = new X509CertSelector();
  		caSelector.setBasicConstraints(0);
  
  		return Arrays.asList(digSigSelector, caSelector);
  	}
docs: {@inheritDoc}