Communications in Theoretical Physics
A Novel Quantum Covert Channel Protocol Based on Any Quantum Secure Direct Communication Scheme
Shujiang Xu, Xiu‐Bo Chen, Xinxin Niu, Yixian Yang
Abstract
By analyzing the basic properties of unitary transformations used in a quantum secure direct communication (QSDC) protocol, we show the main idea why a covert channel can be established within any QSDC channel which employs unitary transformations to encode information. On the basis of the fact that the unitary transformations used in a QSDC protocol are secret and independent, a novel quantum covert channel protocol is proposed to transfer secret messages with unconditional security. The performance, including the imperceptibility, capacity and security of the proposed protocol are analyzed in detail.