  This paper investigates the physical layer security (PLS) of a broadband
in-home power line communication (PLC) system when a malicious wireless device
tries to eavesdrop private messages exchanged between two PLC devices. Such a
security issue arises when electric power circuits, which are used for data
communication, are constituted by unshielded power cables. In this regard, the
hybrid wiretap channel model for formulating achievable secrecy rate and
secrecy outage probability is considered. Additionally, a data set of channel
estimates and measured additive noises obtained from a measurement campaign
carried out in several in-home facilities is used for providing practical
results, which can offer direction for dealing with the security aspects of
broadband in-home PLC systems in the physical layer perspective. The attained
results show high values of secrecy outage probability for all chosen values of
target secrecy rate and total power transmission (practical and theoretical)
when the PLC devices are far from each other and the eavesdropper is close to
the PLC transmitter (i.e., the distance is shorter than 2 meters). Overall, the
numerical results show that the vulnerability of broadband in-home PLC systems,
in terms of PLS, is relevant when practical values of total transmission power
apply. Therefore, a rethinking of the use of unshielded power cables or new
designs of the broadband in-home PLC system deserves special attention for
ensuring security at the physical layer.
