  Physical layer security is a useful tool to prevent confidential information
from wiretapping. In this paper, we consider a generalized model of
conventional physical layer security, referred to as hierarchical information
accessibility (HIA). A main feature of the HIA model is that a network has a
hierarchy in information accessibility, wherein decoding feasibility is
determined by a priority of users. Under this HIA model, we formulate a sum
secrecy rate maximization problem with regard to precoding vectors. This
problem is challenging since multiple non-smooth functions are involved into
the secrecy rate to fulfill the HIA conditions and also the problem is
non-convex. To address the challenges, we approximate the minimum function by
using the LogSumExp technique, thereafter obtain the first-order optimality
condition. One key observation is that the derived condition is cast as a
functional eigenvalue problem, where the eigenvalue is equivalent to the
approximated objective function of the formulated problem. Accordingly, we show
that finding a principal eigenvector is equivalent to finding a local optimal
solution. To this end, we develop a novel method called generalized power
iteration for HIA (GPI-HIA). Simulations demonstrate that the GPI-HIA
significantly outperforms other baseline methods in terms of the secrecy rate.
