The energy cost of cryptographic key establishment in wireless sensor networks

Wireless sensor nodes generally face serious limitations in terms of computational power, energy supply, and network bandwidth. Therefore, the implementation of effective and secure techniques for setting up a shared secret key between sensor nodes is a challenging task. In this paper we analyze and compare the energy cost of two different protocols for authenticated key establishment. The first protocol employs a lightweight variant of the Kerberos key transport mechanism with 128-bit AES encryption. The second protocol is based on ECMQV, an authenticated version of the elliptic curve Diffie-Hellman key exchange, and uses a 256-bit prime field GF(p) as underlying algebraic structure. We evaluate the energy cost of both protocols on a Rockwell WINS node equipped with a 133 MHz Strong ARM processor and a 100 kbit/s radio module. The evaluation considers both the processor's energy consumption for calculating cryptographic primitives and the energy cost of radio communication for different transmit power levels. Our simulation results show that the ECMQV key exchange consumes up to twice as much energy as Kerberos-like key transport.