Secret key generation using a relay with precoding in the null space

Abstract

A method comprising transmitting, by a first communication node (), a first communication; receiving, by a relay node (), the first communication and estimating a first communication channel (H; H). Transmitting, by a second communication node (), a second communication; receiving, by the relay node (), the second communication; and estimating a second communication channel (G, G); generating a first transmission signal (x; x); transmitting, by the relay node (), the first transmission signal (x; x); generating, by the first communication node (), a first instance of the encryption key (κ) based on a first received signal (r); generating, by the second communication node (), a second instance of the encryption key (κ) based on a second received signal (r), wherein: the transmission signal (x) is generated such that the first received signal (r) is equal to the second received signal (r).