Building Secure Cryptographic Transforms, or How to Encrypt and MAC

We describe several notions of “cryptographic transforms,” symmetric schemes designed tomeet a variety of privacy and authenticity goals. We consider goals, such as replay-avoidanceand in-order packet delivery, that have not been fully addressed in previous works in this area.We then provide an analysis of possible ways to combine standard encryption and messageauthentication schemes in order to provably meet these goals. Our results further narrow thegap between the provable-security results from the theoretical community and the needs ofdevelopers who implement real systems.