Efficient Key Generation and Distributionon Wireless Sensor Networks

Abstract: Wireless Sensor Networks have become popular during the last years. The introduction ofIPv6 which broadened the address space available, IEEE802.15.4 and adaption layers such as6loWPAN have allowed the intercommunication of small devices. These networks are usefulin many scenarios such as civil monitoring, mining, battle eld operations, as well as consumerproducts. Hence, practical security solutions for the intercommunication must be provided,ensuring privacy, authenticity, integrity and data freshness. In most cases, WSN nodes arenot tamper-proof and have very limited available resources and capabilities which makes PKIcurrently not attractive for this environment. At the same time, key pre-distribution providetoo low security for most applications. Therefore, the communication bootstrapping or thekey generation and distribution problem is an important concern to be addressed with theadditional di culty of the constrained capabilities of WSN nodes. In this thesis, a solution tothis problem is described. It makes use of ECDH and the curve K-163 for key exchange, AESCCM-128 for symmetric encryption to lower the processing overhead and a partial challengesolving chain as well as a TAS to provide strong authentication. Several hash functions havebeen analysed as well as several random number generating approaches. At the same time, inorder to t the key generation and distribution algorithms together with the regular sensoroperation, code optimizations were carried out on the cryptographic library Relic-Toolkit,reducing the memory footprint in 4KB; code reductions on Contiki OS allowed it to run usingonly 18KB of ash; and the peripheral drivers developed for the CC430 reduced as well thecomputation time. The solution allows to generate and distribute the keys in situ and isproved to be resilient to most adversaries while taking into account scalability, portability,energy consumption and making it suitable for consumer applications.