The use of energy management systems allows the management of electrical loads and resources inside a building. The variety of models allows end-users to optimize their energy usage considering multiple constraints while considering the end-users context and preferences. However, the sharing of data among users and entities, especially external entities, such as microgrid operators, energy community operators, and aggregators is an issue that needs to be addressed to protect data privacy. The proposed solution solves this issue by using signed tokens while being compliant with the European General Data Protection Regulation. The proposed solution is presented in this paper and demonstrated using real data regarding an office building. The results demonstrated the potential of this solution and the possibility of its use to protect the ownership rights of data, given the power to the owner and allow them to define the permissions of each data.