SHAKE: Single HAsh key establishment for resource constrained devices

Pairwise secret key establishment leveraging properties of the wireless channel, is an effective security means in scenarios where no common secret or PKI is available. Related work has shown that secret bit streams can be extracted from, e.g., signal strength ratio measurement between two peers. However, they all require a considerable amount of computing resources by the two parties. In this paper we present SHAKE, a novel algorithm to establish a key using the physical properties of the wireless channel. SHAKE is particularly suitable for scenarios where the two peers have very diverse computational resources. For example, SHAKE can be used to establish a key between a sensor and the sink in a Wireless Sensor Network. We show that a secret key can be established shifting the computational burden on one peer while the other party only require one hash evaluation, what can be afforded by any resource constrained device. We evaluate SHAKE through theoretical analysis and provide validation through real world measurements. According to our experiments, the proposed protocol generates high-entropy bit at remarkable rates and enjoys minimal computational complexity requirements at one of the two parties.