Secure communication in K-user multi-antenna broadcast channel with state feedback

Sheng Yang (1) , Mari Kobayashi (1)

1 L2S - Laboratoire des signaux et systèmes

In this paper, we consider the secure communication in a K-user multi-antenna broadcast channel (BC) with state feedback. We characterize the optimal secure degrees of freedom (SDoF) region of multiple-input single-output (MISO) channel. The SDoF region is achievable by a secret key based linear scheme, which generates analog secret keys by sending artificial noise and then performs space-time alignment scheme secured by these secret keys. The optimality is proved by deriving a new outer bound on the capacity region in a systematic way. Interestingly, the proposed outer bounding technique also applies to the erasure broadcast channel and provides a simpler proof as compared to the existing one. Finally, an explicit connection between the multi-antenna BC and the erasure BC is revealed. We show that, with a large number of users, secrecy cannot be guaranteed in the erasure BC, while it comes almost " for free " in the multi-antenna BC when the number of transmit antennas grows accordingly.

Domains: Information Theory [cs.IT]

Sheng Yang, Mari Kobayashi. Secure communication in K-user multi-antenna broadcast channel with state feedback. IEEE International Symposium on Information Theory - (ISIT 2015), Jun 2015, Hong Kong, China. pp.1976-1980, ⟨10.1109/ISIT.2015.7282801⟩. ⟨hal-01261220⟩