Implementation of physical layer key sharing schemes using Software Defined Radios

We present implementations of two secret key sharing schemes over a Gaussian wire-tap channel and an error-free public side channel. Information-theoretic secrecy is the basis for these schemes. The first scheme uses only one-way communication between transmitter and receiver. In this case, without interaction, we share randomness from transmitter to receiver and extract a secret key from this randomness with the help of extra information sent by the transmitter on the side channel. In this scheme, we show it is possible to agree on a secret key, if the channel conditions between transmitter and receiver are better than that of the transmitter and any eavesdropper. The second scheme is with two-way communication between transmitter and receiver. In this case, we model the AWGN channel as a Binary Symmetric Channel, and show that it is possible for secret key sharing even if the transmitter-eavesdropper channel quality is better than that of the transmitter-receiver channel. We present simulation and experimental results for both these schemes with the help of Software Defined Radio tools.