On key agreement in wireless sensor networks based on radio transmission properties

Recently, several research contributions have justified that wireless communication is not only a security burden. Its unpredictable and erratic nature can also be turned against an adversary and used to augment conventional security protocols, especially key agreement. In this paper, we are inspired by promising studies on such key agreement schemes, yet aim for releasing some of their limiting assumptions. We demonstrate the feasibility of our scheme within performance-limited wireless sensor networks. The central idea is to use the reciprocity of the wireless channel response between two transceivers as a correlated random variable. Doing so over several frequencies results in a random vector from which a shared secret is extracted. By employing error correction techniques, we are able to control the trade-off between the amount of secrecy and the robustness of our key agreement protocol. To evaluate its applicability, the protocol is implemented on MicaZ sensor nodes and analyzed in indoor environments. Further, these experiments provide insights into realistic channel behavior, available information entropy, and show a high rate of successful key agreements, up to 95%.