Wireless network coding with physical-layer security

Today, relaying at routers is secure because we encrypt the confidential messages. We allow routers to have full access to contents of received packets and rest assured that the confidential contents cannot be decrypted, with the underlying assumption that adversaries in the network including the routers are computationally bounded. Nonetheless, as technology develops, much higher computational capability may be achieved. The network is not secure any more when routers or eavesdroppers at routers have infinite computational power. Indeed, there are non-computational security based schemes against external eavesdroppers, which make the eavesdroppers fail in receiving correct data, but unfortunately they cannot be used for security at routers, because we need to achieve not only security but also error-free data forwarding at routers, which is much more challenging. This paper proposes secure wireless network coding to achieve physical-layer security at routers by taking advantages of interference and noise, which are usually considered harmful. We exploit the interference to design network coding protocols to achieve not only security, but also error-free data forwarding at a high rate. Noise, which leads to the randomness of wireless channels, also contributes to providing security in our scheme. With the help of both interference and noise, wireless network coding can be a crucial approach to achieve security at routers, which traditional store-and-forward routing cannot achieve.