title: Quantum exhaustive key search with simplified-DES as a case study.
abstract: To evaluate the security of a symmetric cryptosystem against any quantum attack, the symmetric algorithm must be first implemented on a quantum platform. In this study, a quantum implementation of a classical block cipher is presented. A quantum circuit for a classical block cipher of a polynomial size of quantum gates is proposed. The entire work has been tested on a quantum mechanics simulator called libquantum. First, the functionality of the proposed quantum cipher is verified and the experimental results are compared with those of the original classical version. Then, quantum attacks are conducted by using Grover's algorithm to recover the secret key. The proposed quantum cipher is used as a black box for the quantum search. The quantum oracle is then queried over the produced ciphertext to mark the quantum state, which consists of plaintext and key qubits. The experimental results show that for a key of n-bit size and key space of N such that [Formula: see text], the key can be recovered in [Formula: see text] computational steps.
authors.affiliation: School of Computer Sciences, Universiti Sains Malaysia (USM), 11800 Minden, Pulau Pinang Malaysia.
authors.forename: Mishal
authors.initials: M
authors.lastname: Almazrooie
authors.affiliation: School of Computer Sciences, Universiti Sains Malaysia (USM), 11800 Minden, Pulau Pinang Malaysia.
authors.forename: Azman
authors.initials: A
authors.lastname: Samsudin
authors.affiliation: School of Computer Sciences, Universiti Sains Malaysia (USM), 11800 Minden, Pulau Pinang Malaysia.
authors.forename: Rosni
authors.initials: R
authors.lastname: Abdullah
authors.affiliation: School of Physics, Universiti Sains Malaysia (USM), 11800 Minden, Pulau Pinang Malaysia.
authors.forename: Kussay N
authors.initials: KN
authors.lastname: Mutter
keywords: Block cipher; Grover search; Quantum cryptanalysis; Quantum simulation; Symmetric cryptography