Abstract: AES is currently the most widely used internationally standardized block cipher algorithm.The National Institute of Standards and Technology(NIST) uses the quantum security strength of AES as a reference for evaluating the security of post-quantum cryptography.Therefore,implementing the quantum circuit of the AES algorithm and analyzing its quantum security has become a research hotspot in cryptography.However,since implementing the AES algorithm’s quantum circuit requires hundreds of qubits and tens of thousands of quantum gates,making the implementation and optimization of Simplified AES quantum circuits has become an important research direction.This study successfully implements the S-box quantum circuit using the DORCIS tool based on the S-box lookup table,decomposes the CCCNOT gate into four Toffoli gates by borrowing one qubit,and avoids swap gates in shift operations by permuting variables.Additionally,an 8-qubit S-box quantum circuit for key expansion is designed and implemented using the Boolean expression of the S-box.The optimized S-AES quantum circuit is verified in the Qiskit Aer simulator,requiring only 32 qubits,51 NOT gates,220 CNOT gates,and 120 Toffoli gates.Compared to existing me-thods,this approach significantly reduces quantum resource consumption,enhancing the efficiency of implementing the Simplified AES quantum circuit.

Key words: Block cipher, Simplified AES, S box, Quantum circuit, Boolean expression