Yuanjing Zhang

In distributed systems, Byzantine consensus serves as a practical approach to addressing the Byzantine general problem. Previous research has exploited quantum resources to develop quantum-detectable Byzantine consensus protocols, aiming to surpass the 1/3 fault-tolerance bound. However, these consensus protocols are designed under the assumption of secure channel. They ignored malicious participants' attacks on the communication process. In this paper, we introduce a new quantum protocol for quantum Byzantine consensus utilizing the full quantum one-way function, which is the foundation for generating verification state in list distribution phase and secure message in agreement phase. By relying on the quantum circuit of the full quantum one-way function, the honest participants are able to reach consensus, while the malicious participants are effectively detected. In order to enhance the scalability of the proposed quantum Byzantine consensus protocol, we categorize the participants into three-member groups when the number of participants is n > 3. Meanwhile, the election of commander is introduced in agreement phase. In the proposed multi-party quantum Byzantine consensus protocol, the full quantum one-way function verifies the honesty of the participants both in list distribution phase and agreement phase. Security analysis demonstrates that the proposed multiparty quantum Byzantine consensus protocol is secure against quantum attacks and the dishonest behaviors of participants.

Fully homomorphic encryption enables computation on encrypted data while maintaining secrecy. This leads to an important open question whether quantum computation can be delegated and verified in a non-interactive manner or not. In this paper, we affirmatively answer this question by constructing quantum fully homomorphic encryption (QFHE) schemes with quantum obfuscation. For different scenarios, we propose two QFHE schemes with multi-valued quantum point obfuscation. One is with single-qubit point obfuscation and the other is with multi-qubit point obfuscation. The correctness of two QFHE schemes is proved theoretically. The evaluator does not know the decryption key and does not require a regular interaction with a user. The output state has the property of complete mixture, which guarantees the security. Moreover, the security level of the QFHE schemes depends on quantum obfuscation and encryption operators.