public void verifyPostBindingSignature(Document document, PublicKey publicKey)
     throws VerificationException {
   SAML2Signature saml2Signature = new SAML2Signature();
   try {
     if (!saml2Signature.validate(document, publicKey)) {
       throw new VerificationException("Invalid signature on document");
     }
   } catch (ProcessingException e) {
     throw new VerificationException("Error validating signature", e);
   }
 }