## Cryptology ePrint Archive: Report 2017/1247

Block encryption of quantum messages

Min Liang and Li Yang

Abstract: In modern cryptography, block encryption is a fundamental cryptographic primitive. However, it is impossible for block encryption to achieve the same security as one-time pad. Quantum mechanics has changed the modern cryptography, and lots of researches have shown that quantum cryptography can outperform the limitation of traditional cryptography.

This article focuses on block encryption of quantum data. Based on pseudorandom functions, we construct a quantum block encryption (QBE) scheme, and prove it has indistinguishable encryption under chosen plaintext attack. Moreover, the combination of the QBE and quantum message authentication scheme has indistinguishable encryption under chosen ciphertext attack. In addition, QBE can achieve perfect security in a particular case. Comparing with quantum one-time pad (QOTP), QBE scheme can be the same secure as QOTP, and the secret key can be reused (no matter whether the eavesdropping exists or not). Thus, block encryption based on quantum mechanics can break the limitation of perfectly secure encryption, and can be used as the new cryptographic primitive instead of QOTP. In order to physically implement the QBE scheme, we only need to implement two kinds of single-qubit gates (Pauli $X$ gate and Hadamard gate), so it is within reach of current quantum technology.

Category / Keywords: secret-key cryptography / Quantum cryptography, quantum encryption, block encryption, quantum pseudorandom functions, perfect security