Efficient broadcast authentication for Wireless Sensor and Actuator Networks

In the last decade, broadcast authentication for Wireless Sensor and Actuator Networks (WSANs) has evolved to a prosperous research topic. There basically exist two different approaches to verify a message´s originator. On the one hand, public-key cryptography is well-suited to sign and verify messages. However, this may not be feasible for low-cost, lowpower nodes with limited processing capabilities as can be found in WSANs. On the other hand, schemes that are based on symmetric-key cryptography require some kind of asymmetry which is crucial for broadcast authentication. Plenty of them are based on the TESLA protocol. TESLA achieves asymmetry by the use of one-way key chains with delayed disclosure of keys by requiring time synchronization. However, the authentication delay introduced by TESLA leads to some major disadvantages. This paper addresses the security demands of WSANs and proposes a broadcast authentication scheme allowing instantaneous message authentication. The basic scheme is further extended with a probabilistic model. The proposed concept is theoretically analyzed and the improvement of the security level is examined. Furthermore, storage requirements and the computational effort are investigated and compared to other approaches. Finally, a typical use case, i.e., streetlight management, is depicted.