Quantum Private Comparison without Classical Computation

There are usually two kinds of signals i.e. quantum and classical to process in lots of existing protocols of quantum private comparison (QPC), for they employ quantum technology and classical computation to implement security and comparison, respectively. Classical operations and their information are prone to classical attacks with insufficient security. Therefore, a protocol of quantum gate-based QPC has been proposed without classical operations, but it is only applicable for qubits of computational basis. For its application to diagonal basis, this paper uses quantum gates and GHZ states to propose a new QPC protocol without classical data to process. There being no classical computation could lead to the improvement of security. The presented protocol is not only simple and efficient but also broadening applicable occasions. The analyses indicate its correctness and security.