Mathematical Methods of Cryptography

Quantum cryptanalysis of the KB-256 block cipher

M. V. Polyakov^ab, A. M. Koreneva<sup>ac

a</sup> "Security Code", Moscow
^b Bauman Moscow State Technical University
^c Financial University under the Government of the Russian Federation, Moscow

Abstract: In this paper, we present the results of a quantum cryptanalysis of the KB-256 block cipher. First of all, we have obtained the complexity of quantum circuit implementation. This quantum circuit is a part of the oracle in Grover's algorithm. As a result, such an attack would require at least 1068 qubits and 188892 quantum gates. Also, in our analysis we have found that the cipher is resistant to attacks based on searching hidden linear structures.

Keywords: quantum cryptanalysis, Grover's search, quantum circuits, hidden linear functions.

UDC: 519.7

DOI: 10.17223/2226308X/17/25