Relay system can improve the secrecy of a wireless communication with physical layer security algorithms.Most of these algorithms include two stages:during the first stage

the source node sends coded messages to the relays

and during the second stage

the relays forward the received messages to the destination node.Usually

there is no protection during the first stage

thus most of the secrecy analysis is based on the assumption that there is no direct channel between the source and the eavesdropper.In a practical system

when the eavesdropper is located near the source

the secrecy rate of all these algorithms is down to zero.In this paper

a novel three-stage algorithm with hybrid signals is proposed

which can offer full protection on a relay system.The algorithm results in a non-convex optimal problem

and a sub-optimal solution with low computational complexity is proposed.The theoretical analysis and simulation results show that the proposed scheme can achieve much better secrecy performance than traditional algorithms when the eavesdropper is near the source node.