Quantum Implementation and Analysis of DEFAULT.

In this paper, we present the quantum implementation and analysis of the recently proposed block cipher, DEFAULT. This cipher consists of two components, namely DEFAULT-LAYER and DEFAULT-CORE. Two instances of DEFAULT-LAYER are used before and after DEFAULT-CORE (in the so-called ‘sandwich construction’). We discuss the various choices made to keep the cost for the basic quantum circuit and that of the Grover’s oracle search, and compare it with the levels of quantum security specified by the United States’ National Institute of Standards and Technology (NIST). All in all, our work fits in the research trend of finding the possible quantum vulnerability of symmetric key ciphers.