Abstract. Sensor networks offer the advantages of simple and low-resource communication. Nevertheless, security is of particular importance in many cases such as when sensitive data is communicated or tamper-resistance is required. Updating the security keys is one of the key points in security, which restrict the amount of data that may be exposed when a key is compromised. In this paper, we propose novel key update methods, and benefiting from stochastic model checking we propose a novel method for determining optimal key update strategies for custom network scenarios. We also present a case study where an application in commercial building automation is considered.