Individual Secrecy for the Broadcast Channel

TL;DR

This paper investigates secure broadcast communication ensuring individual secrecy constraints, developing achievable rate regions and characterizing capacity for special cases, including deterministic and Gaussian models, with practical trade-offs.

Contribution

It introduces new achievable rate regions for individual secrecy in broadcast channels, extending existing coding techniques and characterizing capacity in key scenarios.

Findings

Capacity region for deterministic case established.

Constant gap of 0.5 bits for Gaussian model.

Trade-off between secrecy level and throughput demonstrated.

Abstract

This paper studies the problem of secure communication over broadcast channels under the individual secrecy constraints. That is, the transmitter wants to send two independent messages to two legitimate receivers in the presence of an eavesdropper, while keeping the eavesdropper ignorant of each message (i.e., the information leakage from each message to the eavesdropper is made vanishing). Building upon Carleial-Hellman's secrecy coding, Wyner's secrecy coding, the frameworks of superposition coding and Marton's coding together with techniques such as rate splitting and indirect decoding, achievable rate regions are developed. The proposed regions are compared with those satisfying joint secrecy and without secrecy constraints, and the individual secrecy capacity regions for special cases are characterized. In particular, capacity region for the deterministic case is established, and for the Gaussian model, a constant gap (i.e., 0.5 bits within the individual secrecy capacity region) result is obtained. Overall, when compared with the joint secrecy constraint, the results allow for trading-off secrecy level and throughput in the system.