Given the sensitivity of the potential applications of wireless sensor networks, security emerges as a challenging issue in these networks. Because of the resource limitations, symmetric key establishment is one favorite paradigm for securing WSN. One of the main concerns when designing a key management scheme for WSN is the network scalability. Indeed, the protocol should support a large number of nodes to enable a large scale deployment of the network. In this paper, the authors propose a new highly scalable key establishment scheme for WSN. For that purpose, they make use, for the first time, of the until design theory.