Cryptanalysis of quantum secure direct communication protocol with mutual authentication based on single photons and Bell states

Recently, Yan et al. proposed a quantum secure direct communication (QSDC) protocol with authentication using single photons and Einstein-Podolsky-Rosen (EPR) pairs (Yan L. et al., Comput. Mater. Contin., 63 (2020) 1297). In this work, we show that the above QSDC protocol is secure neither against intercept-and-resend attack, nor against impersonation attack. With any of these two types of attacks, an eavesdropper can recover the full secret message. We also propose a suitable modification of this protocol, which not only defeats the above attacks, but also resists all other common attacks. Thus, our modified protocol provides an improvement over the existing one in terms of security. Copyright (C) 2022 EPLA