Key management is the basic building block of all the security protocols and is one of the most challenging issues in wireless sensor networks (WSNs). Centralising a trusted key management server is not an appropriate solution in such fully distributed networks. On the other hand, designing a distributed key management system is a challenging task, due to the constrained characteristics of sensor nodes, which are limited in storage, computation, communication, and energy. In the literature, there is a hot research effort on key management purpose for WSNs. The greatest part of the existing solutions focuses mainly on the optimisation of the key number, rekeying frequency and process or the encryption system of the distributed keys. Unfortunately, these systems are implemented as an additional and independent service, involving a considerable overhead. In this study, the authors propose µKMS (micro key management system) for WSNs. µKMS implements a dissimulation scheme, embedding the rekeying process messages on the unexploited coding space of the exchanged ZigBee packets. They have developed simulations, where the obtained results show the relevance of µKMS in terms of communication overhead, storage overhead, and energy consumption.