  Employing reconfigurable intelligent surfaces (RIS) is emerging as a
game-changer candidate, thanks to their unique capabilities in improving the
power efficiency and supporting the ubiquity of future wireless communication
systems. Conventionally, a wireless network design has been limited to the
communicating end points, i.e., the transmitter and the receiver. In general,
we take advantage of the imposed channel state knowledge to manipulate the
transmitted signal and to improve the detection quality at the receiver. With
the aid of RISs, and to some extent, the propagation channel has become a part
of the design problem. In this paper, we consider a single-input single-output
cooperative network and investigate the effect of using RISs in enhancing the
physical layer security of the system. Specifically, we formulate an
optimization problem to study the effectiveness of the RIS in improving the
system secrecy by introducing a weighted variant of the secrecy capacity
definition. Numerical simulations are provided to show the design trade-offs
and to present the superiority of RIS-assisted networks over the conventional
ones in terms of the system's secrecy performance.
