We study secret communication for broadcast channels with two legitimate receivers and one eavesdropper. The transmitter sends two independent confidential messages to the legitimate receivers which have to be kept secret from the eavesdropper. Here, each legitimate receiver is interested in one confidential message having the other one already as side information available. This problem arises for example in the broadcast phase in a bidirectional relay network, where a relay node establishes a bidirectional communication between two nodes while keeping the communication secure from an eavesdropper outside the network. We provide achievable rate regions and an outer bound on the secrecy capacity region.
We study secret communication for broadcast channels with two legitimate receivers and one eavesdropper. The transmitter sends two independent confidential messages to the legitimate receivers which have to be kept secret from the eavesdropper. Here, each legitimate receiver is interested in one confidential message having the other one already as side information available. This problem arises for example in the broadcast phase in a bidirectional relay network, where a relay node establishes a bidirectional communication between two nodes while keeping the communication secure from an eavesdropper outside the network. We provide achievable rate regions and an outer bound on the secrecy capacity region.
We study secure communication in which two confidential messages are transmitted over a broadcast channel to two legitimate receivers, while keeping an eavesdropper ignorant. Each legitimate receiver is interested in decoding one confidential message, while having the other one as side information. In order to measure the secrecy of the communication, we investigate two different secrecy criteria: joint secrecy and individual secrecy. For both criteria, we provide an achievable rate region and a matching multi-letter outer bound presenting a multi-letter description for the capacity region. We further investigate the class of more capable channels and provide a single-letter converse establishing the secrecy capacity region, not only for more capable channels but less noisy and degraded channels as well. Our results indicate that the secrecy capacity for individual secrecy is higher than the one for joint secrecy, as one message can be used as a secret key for the other one.
In this article, a broadcast channel in the degraded state with two legitimate receivers in the attendance of an eavesdropper has been studied, where, the sender demands to forward two independent confidential messages that ought to be kept as secret as feasible of the eavesdropper to the legitimate receivers. In the studied system, it has been supposed that the non-causal channel state information has been considered at the transmitter side and every one of receivers has the message forwarded via source demanded via the further one. The model studied in this paper is further generalized into the formerly considered broadcast channel with confidential messages and considering side information in the receiver. It has been supplied an outer bound by considering confidentially conditions for proposed system.
The use of secret keys in broadcast channels with receiver side information is studied. The particular scenario is analyzed where a transmitter wants to send two confidential messages to two receivers, while keeping an external eavesdropper ignorant. Each receiver has one of the confidential messages as side information available for decoding. In addition to that, the transmitter shares independent secret keys of arbitrary rates with both receivers. The secret keys can be used in different ways: They can act as one-time pads to encrypt the confidential messages or they can be used as randomization resources for wiretap coding. Both approaches are discussed and an achievable rate region based on superposition coding is established for the one-time pad approach. For the wiretap coding approach, the secrecy capacity for degraded channels is derived. In the optimal coding scheme, the available secret keys are used as the randomization part of the wiretap code to keep the eavesdropper ignorant. In establishing the capacity region, a new upper bound on the sum-rate is derived. This bound shows that in an optimal coding scheme, in the degraded case, the total equivocation-rate of the (opposite) secret-keys at the legitimate receivers must equal the equivocation-rate of the secret-keys at the eavesdropper, when informed about the messages.
In this work, the bidirectional broadcast channel (BBC) with confidential messages is studied. The problem is motivated by the concept of bidirectional relaying in a three-node network, where a half-duplex relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol and thereby transmits additional confidential information to one of them in the broadcast phase. The corresponding confidential message is transmitted at a certain secrecy level which characterizes the amount of information that can be kept secret from the non-legitimate node. The capacity-equivocation and secrecy capacity regions of the BBC with confidential messages are established where the latter characterizes the communication scenario with perfect secrecy, which means that the confidential information is completely hidden from the non-legitimate node. Thereby, it is shown that the optimal processing exploits ideas and concepts of the BBC with common messages and of the classical broadcast channel with confidential messages.
Recent research developments show that the concept of bidirectional relaying significantly improves the performance in wireless networks. This applies to three-node networks, where a half-duplex relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol. In this work we consider the scenario when in the broadcast phase the relay transmits additional confidential information to one node, which should be kept as secret as possible from the other, non-intended node. This is the bidirectional broadcast channel with confidential messages for which we derive the capacity-equivocation region and the secrecy capacity region. The latter characterizes the communication scenario with perfect secrecy, where the confidential message is completely hidden from the non-legitimated node.
This paper studies the problem of secure communication over the broadcast channel with receiver-side information under the lens of individual secrecy constraints, that is, the transmitter wants to send two independent messages to two receivers, which have, respectively, the desired message of the other receiver as side information, while keeping the eavesdropper ignorant of each message (i.e., the information leakage rate from each message to the eavesdropper is made vanishing). Building upon one-time pad, secrecy coding, and broadcasting schemes, achievable rate regions are investigated, and the capacity region for special cases of either a weak or strong eavesdropper (compared to both legitimate receivers) is characterized. Interestingly, the capacity region for the former corresponds to a line and the latter corresponds to a rectangle with missing corners; a phenomenon occurring due to the coupling between user's rates. Moreover, the individual secrecy capacity region is also fully characterized for the case where the eavesdropper's channel is deterministic. In addition to discrete memoryless setup, Gaussian scenarios are studied. For the Gaussian model, in addition to the strong and weak eavesdropper cases, the capacity region is characterized for the low and high SNR regimes when the eavesdropper's channel is stronger than one receiver but weaker than the other. Remarkably, positive secure transmission rates are always guaranteed under the individual secrecy constraint, unlike the case of the joint secrecy constraint (i.e., the information leakage rate from both messages to the eavesdropper is made vanishing). Thus, this notion of secrecy serves as an appropriate candidate for trading off secrecy level and transmission rate, making secrecy more affordable but still acceptable to the end user.