Computationally and Resource Efficient Group Key Agreement for Ad Hoc Sensor Networks

Abstract

Secure and reliable group communication is an important aspect of security in distributed ad hoc sensor networks. Most sensors are built to be inexpensive, low power devices and consequently have limited computational and communication resources. Constraints in resources make most conventional security protocols, such as Diffie-Hellman key exchange impractical. This work adapts existing work on tree-based group key agreement that combines key trees with Diffie-Hellman key exchange, by replacing expensive public key operations with relatively cheaper symmetric key operations. The modular exponentiations in Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> * used in Diffle-Hellman key exchange are replaced by polynomial evaluations in GF(2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sup> ) Galois fields, thereby reducing the code space and time complexity requirements for the protocols substantially. This makes the protocol adaptable for use on resource-constrained sensor networks. We also focus on secure and efficient group key management in the case of group mutation. Our group key management scheme will set up a per-session shared secret key among the group members when new members join or existing members leave the group. We also discuss a performance analysis of our scheme wherein we show that our protocol is efficient in terms of computational and memory requirements.