Collaborative authentication in unattended WSNs

An unattended wireless sensor network (UWSN) might collect valuable data representing an attractive target for the adversary. Since a sink visits the network infrequently, unattended sensors cannot immediately off-load data to some safe external entity. With sufficient time between sink visits, a powerful mobile adversary can easily compromise sensor-collected data. In this paper, we propose two schemes (CoMAC and ExCo) that leverage sensor co-operation to achieve data authentication. These schemes use standard (and inexpensive) symmetric cryptographic primitives coupled with key evolution and few messages exchange. We provide security analysis for proposed schemes and assess their effectiveness via simulations. We show that proposed schemes cope well with real WSN issues, such as message loss and sensor failure. We also compare the two schemes with respect to robustness and overhead, which allows network designers to carefully select the right scheme and tune appropriate system parameters. Copyright 2009 ACM.