I think your proposed answer sounds fine. Just start off with general aspects of the research and what your specific role is. If there are more specific questions by the interviewer, just reply back that you can't give out too many details due to confidentiality. I'm sure they will understand.
Since it's not literally classified research, seems like you should be able to talk about the sort of techniques you're using or data gathering/synthesis you're doing, without revealing the secret sauce/specific research that's being done.