This paper studies the degraded broadcast channel with rate-limited feedback. The transmitter aims to convey a common message to receiver 1 and 2 in addition to a confidential message intended only for receiver 1. The feedback symbol, independent of the channel outputs, is introduced to serve as a secret key between the transmitter and receiver 1. The capacity-equivocation region of this channel model is obtained. A simpler and more intuitive derivation instead of the recursive argument is used to get the single-letter characterization of the upper bound. Furthermore, a novel coding scheme is presented to achieve the upper bound. This paper also derives the secrecy capacity of this channel which subsumes the secrecy capacity of the degraded wiretap channel with rate-limited feedback.
This paper studies the degraded broadcast channel with rate-limited feedback. The transmitter aims to convey a common message to receiver 1 and 2 in addition to a confidential message intended only for receiver 1. The feedback symbol, independent of the channel outputs, is introduced to serve as a secret key between the transmitter and receiver 1. The capacity-equivocation region of this channel model is obtained. A simpler and more intuitive derivation instead of the recursive argument is used to get the single-letter characterization of the upper bound. Furthermore, a novel coding scheme is presented to achieve the upper bound. This paper also derives the secrecy capacity of this channel which subsumes the secrecy capacity of the degraded wiretap channel with rate-limited feedback.
This paper studies the problem of secure communication over a wiretap channel p(y,z|x) with a secure feedback link of rate Rf, where X is the channel input, and Y and Z are channel outputs observed by the legitimate receiver and the eavesdropper, respectively. It is shown that the secrecy capacity, the maximum data rate of reliable communication while the intended message is not revealed to the eavesdropper, is upper bounded as Cs(Rf) les maxmin/p(x) {I(X;Y), I(X;Y |Z) + Rf}. The proof of the bound crucially depends on a recursive argument which is used to obtain the single-letter characterization. This upper bound is shown to be tight for the class of physically degraded wiretap channels. A capacity-achieving coding scheme is presented for this case, in which the receiver securely feeds back fresh randomness with rate Rf, generated independent of the received channel output symbols. The transmitter then uses this shared randomness as a secret key on top of Wyner's coding scheme for wiretap channels without feedback. Hence, when a feedback link is available, the receiver should allocate all resources to convey a new key rather than sending back the channel output.
This paper studies the problem of secure communication over a degraded wiretap channel p(y, z|x) = p(y|x)p(z|y) with secure feedback link of rate Rf, where X is the channel input, and Y and Z are channel outputs observed by the legitimate receiver and the wiretapper respectively. The secrecy capacity is characterized as Cs{Rf) = maxmin{I(X; Y), I(X; Y|Z) + Rf}. p(x)equation. A capacity-achieving coding scheme is presented, in which the receiver securely feeds back fresh randomness with rate Rf, independent of the received channel output. The transmitter then uses the shared randomness as a secret key on top of Wynerpsilas coding scheme for wiretap channel without feedback. Hence, when the receiver has a means of interacting with the transmitter, he should allocate all resources to convey a new key rather than sending back the channel output. For the converse, a recursive argument is used to obtain the single-letter characterization.
The discrete memoryless broadcast channels (DMBCs) with noiseless feedback are studied. The entire capacity-equivocation regions of two models of the DMBCs with noiseless feedback are obtained. One is the degraded DMBCs with rate-limited feedback; the other is the less and reversely less noisy DMBCs with causal feedback. In both models, two kinds of messages are transmitted. The common message is to be decoded by both the legitimate receiver and the eavesdropper, while the confidential message is only for the legitimate receiver. Our results generalize the secrecy capacity of the degraded wiretap channel with rate-limited feedback (Ardestanizadeh et al., 2009) and the restricted wiretap channel with noiseless feedback (Dai et al., 2012). Furthermore, we use a simpler and more intuitive deduction to get the single-letter characterization of the capacity-equivocation region, instead of relying on the recursive argument which is complex and not intuitive.
In this paper, we investigate the model of degraded broadcast channel with noncausal side information, confidential messages and noiseless feedback. This work is from Steinberg's work on the degraded broadcast channel with noncausal side information, and Csiszár and Körner's work on broadcast channel with confidential messages. In this new model, the transmitter sends a confidential message to the non-degraded receiver, and meanwhile sends a common message to both the degraded and non-degraded receivers. Moreover, the channel for the non-degraded receiver is controlled by channel state information (side information), and it is available to the transmitter in a noncausal manner (termed here noncausal side information). In addition, we assume that there is a noiseless feedback from the output of the channel for the non-degraded receiver to the transmitter, and it helps them share a secret key, which enlarges the degraded receiver's uncertainty about the confidential message. Measuring the uncertainty by equivocation (conditional entropy), the capacity-equivocation region composed of all achievable rates-equivocation triples is determined for this new model. Furthermore, the secrecy capacity is formulated, which provides the best transmission rate with perfect secrecy.
This paper investigates the secure data transmission in the broadcast channel with noiseless feedback by using the information-theoretic method. We consider transmitting a private message and a common message to two receivers, of which the common message is to be decoded by both receivers while the private message is only for the intended receiver. The channel to the intended receiver is assumed to be independent of that to the other receiver. Feedback from the output of the intended receiver is used as a shared secret key to enhance the secrecy in the transmission. The capacity-equivocation region and the secrecy capacity of this new model are obtained. We find the secrecy capacity is enhanced by using feedback, even in the case that the other receiver is in a better position than the intended receiver. In addition, our results generalize the secrecy capacity of the degraded wiretap channel with secure feedback, and the capacity region of the degraded broadcast channel.
From the perspective of secure communication, we study transmitting confidential messages in broadcast channel with action-dependent states. Transmitter aims to convey a common message to both receiver 1 and 2, and a confidential message only to receiver 1. It can take actions to affect the generation of channel states which are causally known to the encoder. The inner and outer bounds on the capacity-equivocation region of such a channel are characterized. The corresponding bounds on the secrecy capacity are also obtained. To achieve the rate-equivocation triples, we construct coding schemes using superposition coding and Wyner's random binning. For the special case where no common message is sent, the inner and outer bounds coincide with each other. A binary example is given to illustrate the results.