The broadcast nature of wireless communications makes it difficult to hide transmitted signals from unauthorized users. To this end, physical-layer security is emerging as a promising paradigm to protect the wireless communications against eavesdropping attacks. The fundamental principle behind physical layer security is to exploit the inherent randomness of noise and communication channels to limit the amount of information that can be extracted at the `bit' level by an unauthorized receiver. In this paper, we investigate physical layer security issues in a two-way relay network. The idea is that when the eavesdropper channel is a degraded version of the main channel, the source and the destination can exchange perfectly secure messages at a non-zero rate. Moreover, we use green base stations as relays. Conventional energy sources are a huge source of atmospheric pollution. The renewable energy sources use natural resources and do not cause any pollution, hence they are termed green energy sources. We evaluate the security performance of cooperative relay transmission in Rayleigh fading environments in terms of secrecy capacity and intercept probability.