Secrecy Capacity of a Class of Wiretap Channels with Side Information at the Transmitter

八郎 藤田

Hachiro Fujita

The wiretap channel with causal/noncausal side information at the transmitter is an extension of the original wiretap channel of Wyner to the multi-user case and has been investigated by several authors. Although much effort has been made to establish the secrecy capacity, it is still elusive even if the wiretap channel is physically degraded. In this paper, for a physically degraded wiretap channel, we show a lower bound on the secrecy capacity for the causal case and an upper bound for the noncausal case. We also show that under a certain condition, the secrecy capacity for the causal case is the same as that for the noncausal case. To illustrate the usefulness of our theoretical result, we introduce the concept of a symmetric wiretap channel with state, for which the above condition is easily checked, and we give some examples in which the secrecy capacity can be computed numerically.

隆太郎 松本, Ryutaroh Matsumoto

Mustafa El-Halabi

Bin Dai, Yuan Luo

In this paper, the model of wiretap channel has been reconsidered for the case that the main channel is controlled by channel state information (side information), and it is available at the transmitter in a noncausal manner (termed here noncausal side information) or causal manner (termed here causal side information). Inner and outer bounds are derived on the capacity-equivocation regions for the noncausal and causal manners, and the secrecy capacities for both manners are described and bounded, which provide the best transmission rate with perfect secrecy. Moreover, for the case that the side information is available at the transmitter in a memoryless manner (termed here memoryless side information), both the capacity-equivocation region and the secrecy capacity are determined. The results of this paper extend the previous work on wiretap channel with noncausal side information by providing an outer bound on the capacity-equivocation region. In addition, we find that the memoryless side information can not help to obtain the same secrecy capacity as that of the causal case, and this is different from the well known fact that the memoryless manner can achieve the capacity of the channel with causal side information.

Fangbiao Li, Zhi Xue

In this paper, we study the discrete memory Multiple Access Wiretap Channel (DM-MAWC) with one common message and non-causal side information. In this channel, two transmitters send a common message to the receivers, meanwhile they both transmit an individual confidential message, which must be kept secret from the second receiver (viewed as a wiretapper) to the first receiver. As the side information is non-causally available at the transmitters, we derive the achievable perfect secrecy capacity region for the MAWC with one common message and non-casual side information available at the transmitters by using Cover's superposition coding and Gelfand-Pinsker random binning coding schemes. The achievable secrecy capacity region of this paper subsumes the region of multiple access wiretap channel with or without common message and without side information as its special cases.