The implementation of a Smart Grid demands a network of two-way communication for interaction between the several devices in the system and the management systems. However, communication between the active devices in the system is a big challenge. In addition to providing communication between a large numbers of devices, it is necessary ensure the security on transmitted information. In this context, the use of mesh networks is an interesting alternative. The main feature of this type of network is the auto configuration of the topology and the high dynamic on active devices. The routing infrastructure is implemented by these devices, through exchange of routing tables between the nodes. Thus, it is necessary prevent unauthorized devices disclose routes or may transmit any data on the network. In this context, the authenticity and the integrity information's can be compromised by a false node. Among the protective measures that can be applied in this case highlights the use of authentication mechanism in each node. In these terms, this work presents a proposal to ensure the authenticity of the participating nodes of a mesh network, through signing the control messages of OLSR protocol via SECOM middleware.