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Hierarchical key management for smart grids

Data transfer in smart grids is sensitive and must be properly protected. However, proven security approaches from the IT world can be used only to a certain extent. In particular, resource limitations in the communication network for the last mile and the field devices must be taken into account, which makes popular asymmetric public key infrastructures difficult to apply. This paper reviews current security architectures and proposes an efficient solution based on symmetric keys, which has advantages for highly resource limited devices and networks. Key management follows a four-level hierarchical approach, where the actual session keys used for regular data exchange in the smart grid can be derived automatically by the field devices to increase system security and save communication bandwidth. Execution time measurements of the cryptographic algorithms demonstrate the efficiency of the approach.