code: public boolean validate(OneKey cnKey) throws CoseException {
          CBORObject obj = CBORObject.NewArray();
          obj.Add(contextString);
          if (objProtected.size() > 0) obj.Add(rgbProtected);
          else obj.Add(CBORObject.FromObject(new byte[0]));
          obj.Add(externalData);
          obj.Add(rgbContent);
          return validateSignature(obj.EncodeToBytes(), rgbSignature, cnKey);
      }
docs: Validate the signature on the message using the passed in key.
  
  @param cnKey key to use for validation
  @return true if the signature validates
  @throws CoseException Errors generated by the COSE module