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.
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.
In this paper, the role of feedback in two-way full-duplex Gaussian channel (TW-FD-GC) is revisited. First, we propose a practical coding scheme for the TW-FD-GC, which is based on the noisy type of the well-known Schalkwijk-Kailath (SK) feedback scheme. We show that though this scheme cannot achieve the capacity of the TW-FD-GC, the codeword length that achieves desired decoding error probability is extremely short. Then, we further prove that the proposed scheme is secure by itself, i.e., the achievable rate region of the proposed scheme is also an achievablesecrecyrate region of the two-way full-duplex Gaussian wiretap channel (TW-FD-GWTC). In addition, for the TW-FD-GWTC, numerical result shows that thesecrecysum rate of our proposed scheme can be as large as those achieved by existing schemes in the literature for some cases. Next, we extend the proposed scheme to the TW-FD-GC with Gaussian state interference non-causally known by the corresponding transmitter. We show that the interference can be perfectly canceled by this extended scheme. Finally, we prove that this extended scheme is also secure by itself, and numerical result shows that this extended scheme may perform better than the existing ones in the literature.
Physical layer security (PLS) in the down-link transmission of Internet of Things (IoT) systems is modeled as the compound wiretap channel (C-WTC). Recently, it has been shown that channel feedback helps to enhance the secrecy capacity of the C-WTC, where the channel feedback is used to generate secret keys protecting the transmitted message from being eavesdropped by the eavesdropper. In this paper, we show that for the Gaussian compound wiretap channel (GC-WTC), a hybrid feedback scheme that combines the existing secret-key type feedback and a variation of the classical Schalkwijk-Kailath (SK) type feedback scheme, performs better than the already existing one in the literature. The study of this paper offers a new option for the enhancement of the PLS in IoT systems.
Physical layer security (PLS) in the down-link transmission of Internet of Things (IoT) systems is modeled as the compound wiretap channel (C-WTC). Recently, it has been shown that channel feedback helps to enhance the secrecy capacity of the C-WTC, where the channel feedback is used to generate secret keys protecting the transmitted message from being eavesdropped by the eavesdropper. In this paper, we show that for the Gaussian compound wiretap channel (GC-WTC), a hybrid feedback scheme that combines the existing secret-key type feedback and a variation of the classical Schalkwijk-Kailath (SK) type feedback scheme, performs better than the already existing one in the literature. The study of this paper offers a new option for the enhancement of the PLS in IoT systems.
The two-user Gaussian broadcast wiretap channel with common message and feedback (GBC-WTC-CM-F) is revisited. Traditionally, achievable secrecy rate of this model is achieved by combining Marton’s coding scheme for the two-user broadcast channel (BC) and the secret-key based feedback scheme, where both of the two feedback links are used to transmit secret keys shared between the transceivers. Recently, it has been shown that for the Gaussian wiretap channel with feedback, the Schalkwijk-Kailath (SK) feedback scheme achieves its secrecy capacity. Then it is natural to ask: can we do better when applying the SK-type scheme to the GBC-WTC-CM-F? In this paper, we answer this question by proposing two kinds of SK-type schemes. Specifically, first, we propose a hybrid scheme where one feedback link is used to transmit a secret key, and the other one is used for SK-type coding. We show that this hybrid scheme may perform better than the existing one in some cases. Next, we show that Ozarow’s extended SK scheme for the two-user Gaussian BC with feedback, where both feedback links are used for SK-type coding, is self-secure (satisfying perfect weak secrecy constraint by itself) and may perform the best. We further show that Ozarow’s scheme is in fact a secure finite blocklength coding scheme, and extend it to the static fading SISO and SIMO cases. Finally, the results of this paper are further explained by numerical examples.
Recently, it has been shown that channel feedback helps to enhance the physical layer security (PLS) of communication systems. The current use of feedback focuses on generating secret keys protecting the transmitted messages, and this feedback scheme is proved to be optimal for some physically degraded channel models. In this paper, we revisit the model of the state-dependent wiretap channel with the noncausal state at the transmitter, which plays an important role in the PLS of the wireless communication systems. We propose a new feedback scheme for this model and show that the proposed new scheme performs better than the already existing secret key-based feedback scheme. The results of this paper are further explained via a Gaussian example.
For bi-directional communication, the most general form of encoders should consider the signals received in the past as inputs. However, in practice, it would also be highly desirable if feedback could be ignored for encoding purposes since this would lead to a simple system design. In this work, we investigate the question of whether and how much loss in secrecy rate would be incurred, if such an approach were taken. To do so, we investigate the role of feedback in secrecy for two three-node two-way channel models. First, we show that feedback is indeed useful for a class of full-duplex two-way wire-tap channels. In this case, when feedback is ignored, the channel is equivalent to a Gaussian degraded relay channel with confidential messages to the relay. The usefulness of feedback is demonstrated by deriving an upper bound for this channel when feedback is ignored, and then proving that, when feedback is used, a secrecy rate higher than this upper bound is achievable. Secondly, we consider the half-duplex Gaussian two-way relay channel where there is an eavesdropper co-located with the relay node, and find that the impact of feedback is less pronounced compared to the previous scenario. Specifically, the loss in secrecy rate, when ignoring the feedback, is quantified to be less than 0.5 bit per channel use when the power of the relay goes to infinity. We also show that this rate region is achievable under a simple time sharing scheme with cooperative jamming, which, with its simplicity and near-optimum performance, is a viable alternative to an encoder using feedback.