Quantum key search with side channel advice

Abstract

Recently, a number of results have been published that show how to combine classical cryptanalysis with quantum algorithms, thereby (potentially) achieving considerable speed-ups. We follow this trend but add a novel twist by considering how to utilise side channel leakage in a quantum setting. This is non-trivial because Grover’s algorithm deals with unstructured data, however we are interested in searching through a key space which has structure due to the side channel information. We present a novel variation of a key enumeration algorithm that produces batches of keys that can be efficiently tested using Grover’s algorithm. This results in the first quantum key search that benefits from side channel information.