  In this paper, we propose a self-dependent two-way secure communication where
two sources exchange confidential messages via a wireless powered untrusted
amplify-and-forward (AF) relay and friendly jammer (FJ). By adopting the time
switching (TS) architecture at the relay, the data transmission is accomplished
in three phases: Phase I) Energy harvesting by the untrusted relay and the FJ
through non-information transmissions from the sources, Phase II) Information
transmission by the sources and jamming transmissions from the FJ to reduce
information leakage to the untrusted relay; and Phase III) Forwarding the
scaled version of the received signal from the untrusted relay to the sources.
For the proposed system, we derive a new closed-form lower bound expression for
the ergodic secrecy sum rate (ESSR). Numerical examples are provided to
demonstrate the impacts of different system parameters such as energy
harvesting time, transmit signal-to-noise ratio (SNR) and the relay/FJ location
on the secrecy performance. The numerical results illustrate that the proposed
network with friendly jamming (WFJ) outperforms traditional one-way
communication and the two-way without friendly jamming (WoFJ) policy.
