The two user multiple-input single-output (MISO) broadcast channel withconfidential messages (BCCM) is studied in which the nature of channel stateinformation at the transmitter (CSIT) from each user can be of the form$I_{i}$, $i=1,2$ where $I_{1}, I_{2}\in \{\mathsf{P}, \mathsf{D},\mathsf{N}\}$, and the forms $\mathsf{P}$, $\mathsf{D}$ and $\mathsf{N}$correspond to perfect and instantaneous, completely delayed, and no CSIT,respectively. Thus, the overall CSIT can alternate between $9$ possible statescorresponding to all possible values of $I_{1}I_{2}$, with each state occurringfor $\lambda_{I_{1}I_{2}}$ fraction of the total duration. The maincontribution of this paper is to establish the secure degrees of freedom(s.d.o.f.) region of the MISO BCCM with alternating CSIT with the symmetryassumption, where $\lambda_{I_{1} I_{2}}=\lambda_{I_{2}I_{1}}$. The main technical contributions include developing a) novel achievableschemes for MISO BCCM with alternating CSIT with security constraints whichalso highlight the synergistic benefits of inter-state coding for secrecy, b)new converse proofs via local statistical equivalence and channel enhancement;and c) showing the interplay between various aspects of channel knowledge andtheir impact on s.d.o.f.
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