The role of noisy feedback in secure communications

Tatsuya Tomaru

Dengfeng Xia, Chuanchuan Yang, Bin Dai

In this paper, the role of feedback in two-way full-duplex Gaussian wiretap channel (TW-FD-GWTC) is revisited. Traditionally, in the TW-FD-GWTC, one direction channel (feedback channel) is used to transmit a secret key which ensures the secure communication over the other direction channel (feedforward channel), i.e., the transmission rate of the feedback channel is sacrificed to ensure the physical layer security (PLS) in the feedforward channel. Can both directions achieve positive secrecy rates? We answer this question by proposing a noisy feedback scheme for the TW-FD-GWTC. In this proposed new scheme, both directions achieve positive secrecy rates, and the maximum secrecy sum rate approaches that in the literature. The study of this paper offers a new option for the enhancement of the physical layer security in two-way full-duplex wiretap channel.

Björn Tackmann

Jincheng Zhang

This paper investigates the feasibility and potential benefits of employing quantum relays to enhance secure communication over noisy channels. Traditional direct quantum communication suffers from signal degradation and loss over extended distances, severely limiting its practical application. We propose a novel architecture utilizing quantum entanglement and measurement feedback, where a relay node acts as an intermediary to amplify and correct quantum signals. The core concept involves establishing entanglement between the sender, receiver, and the relay. Measurements performed by the relay, coupled with feedback, enable the relay to effectively combat channel noise and preserve the integrity of the transmitted quantum information. We formally describe the key protocols and mathematical formulations involved, emphasizing the role of entanglement distillation and quantum error correction. The presented approach offers a promising pathway to overcoming the distance limitations of direct quantum communication and establishing secure quantum networks. This work focuses on theoretical development and lays the groundwork for future experimental investigations.

K. Murali, M. Lakshmanan

Germán Bassi, Pablo Piantanida, Shlomo Shitz Shamai

It is well-known that feedback does not increase the capacity of point-to-point memoryless channels, however, its effect in secure communications is not fully understood yet. In this work, an achievable scheme for the wiretap channel with generalized feedback -based on joint source-channel coding- is presented. This scheme recovers previous results, thus it can be seen as a generalization and unification of several results in the field. Additionally, the Gaussian wiretap channel with noisy feedback is analyzed, and the scheme achieves positive secrecy rates even in unfavorable situations where the eavesdropper experiences a much better channel than the legitimate user.