Work

Quantum related-key attacks on Feistel-like ciphers

Year: 2026

Type: article

Abstract: Quantum attacks employing superposition queries (Q2 model) have been demonstrated to compromise numerous classically secure block-cipher constructions. These attacks embed the target encryption structure into a period-finding problem, which dedicated quantum algorithms, including the Simon and BV algorithms, can solve. After restoring the secret state, attackers can launch an attack by recovering the key (the secret state contains key information) or distinguishing it from random permutations. In this paper, we investigate the quantum security of Feistel-like ciphers in a related-key setting. For several constructions, we demonstrate how to define a periodic function that can be evaluated using the Simon algorithm with only $O(n)$ O ( n ) quantum queries to the encryption oracle, where n represents the block size. This enables secret-state recovery attacks on Type-1/2 generalized Feistel schemes, as well as key-recovery attacks on the Feistel-FK and Misty L-KF constructions. All these attacks achieve an exponential reduction in query complexity compared to the best known classical or quantum methods.

Source: EPJ Quantum Technology

DOI: 10.1140/epjqt/s40507-026-00481-3

Authors: Hong-Wei Sun, Long Zhang, Dan-Dan Li, Zhen-Qiang Li, Rong-Xue Xu, Ke-Jia Zhang

Institutions: Heilongjiang University, Beijing University of Posts and Telecommunications, State Key Laboratory of Cryptology

Language: English

Topic: Cryptographic Implementations and Security

Subfield: Artificial Intelligence

Field: Computer Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,190

Funder: National Natural Science Foundation of China