Quantum Implementations of Block Ciphers

Date

2025-8-26

Author

Çıldıroğlu, Hasan Ozgur

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The emergence of quantum computing demands rigorous reassessment of classical cryptographic primitives, particularly lightweight block ciphers (LBCs). This work addresses this critical need by presenting the first comprehensive quantum implementation and security analysis of the Feistel-based LBCs SLIM and MIBS against quantum cryptanalysis. Leveraging the inherent reversibility of the ciphers, we develop novel ancilla-free quantum circuits optimizing qubit utilization and depth. For SLIM-80, our design achieves 30,404 quantum cost with 112 qubits and depth of 4,066. For MIBS-64 and MIBS-80, we implement circuits with 23,371 and 24,363 quantum costs requiring 128 and 144 qubits, respectively, and a uniform depth of 4,768. We then quantify vulnerability to Grover’s key-search under the NIST PQC security constraint MAXDEPTH. By constructing Grover oracles under inner parallelization with multiple plaintext-ciphertext pairs to suppress false positives, we demonstrate total attack costs of 2^111 for SLIM-80 and MIBS-80, and 2^94 for MIBS-64. These costs fall below NIST’s Level-1 security threshold 2^170, confirming both ciphers’ susceptibility to quantum threats despite their lightweight efficiency. Our methodology establishes a quantum implementation framework for Feistel ciphers, revealing critical trade-offs among qubit efficiency, depth, and quantum resilience.

Subject Keywords

Quantum Circuit Implementation, Lightweight Block Ciphers, Grover Attack, SLIM, MIBS

URI

https://hdl.handle.net/11511/115670

Collections

Graduate School of Applied Mathematics, Thesis