Classical Encryption and Authentication under Quantum Attacks
This addresses the need for robust post-quantum cryptography for secure communication systems, though it is incremental as it builds on prior work by Boneh and Zhandry.
The paper tackles the problem of securing classical encryption and authentication against quantum superposition attacks, where adversaries can evaluate functions in superposition, and it re-proves a result showing that uniformly random functions can serve as secure message-authentication codes under such attacks.
Post-quantum cryptography studies the security of classical, i.e. non-quantum cryptographic protocols against quantum attacks. Until recently, the considered adversaries were assumed to use quantum computers and behave like classical adversaries otherwise. A more conservative approach is to assume that also the communication between the honest parties and the adversary is (partly) quantum. We discuss several options to define secure encryption and authentication against these stronger adversaries who can carry out 'superposition attacks'. We re-prove a recent result of Boneh and Zhandry, stating that a uniformly random function (and hence also a quantum-secure pseudorandom function) can serve as a message-authentication code which is secure, even if the adversary can evaluate this function in superposition.