\r\nis no evaluation that characterizes quantum secure communication

\r\n(QSC) protocols in a complete, general manner. The current paper

\r\naddresses the problem concerning the lack of such an evaluation

\r\nfor QSC protocols by introducing an optimality evaluation, which

\r\nis expressed as the average over the three main parameters of QSC

\r\nprotocols: efficiency, security, and practicality. For the efficiency

\r\nevaluation, the common expression of this parameter is used, which

\r\nincorporates all the classical and quantum resources (bits and qubits)

\r\nutilized for transferring a certain amount of information (bits) in a

\r\nsecure manner. By using criteria approach whether or not certain

\r\ncriteria are met, an expression for the practicality evaluation is

\r\npresented, which accounts for the complexity of the QSC practical

\r\nrealization. Based on the error rates that the common quantum attacks

\r\n(Measurement and resend, Intercept and resend, probe attack, and

\r\nentanglement swapping attack) induce, the security evaluation for

\r\na QSC protocol is proposed as the minimum function taken over

\r\nthe error rates of the mentioned quantum attacks. For the sake of

\r\nclarity, an example is presented in order to show how the optimality

\r\nis calculated.","references":null,"publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 146, 2019"}