Comments on a Double-Blockchain Assisted Data Aggregation Scheme for Fog-Enabled Smart Grid

To comply with the specific requirements of smart grids, Chen et al. proposed a data aggregation scheme by utilizing double blockchains and the Paillier cryptosystem that is an additive homomorphic encryption system for public-key cryptography. Chen et al. claimed that their scheme could resist various attacks and ensure data confidentiality, data integrity, validity, identity anonymity and authenticity. However, after thoroughly analyzing their scheme, we find that it suffers from five flaws. Firstly, anonymity is not ensured as claimed. Secondly, private keys of smart meters and fog nodes can be easily retrieved. Thirdly, after a smart meter or a fog node’s private key is revealed, a malicious entity can impersonate it and generate a valid signature of the forged data’s ciphertext. Fourthly, in both of the UA-blockchain generation phase and FA-blockchain generation phase, the signature verification will never succeed. Fifthly, some statements in Chen et al.’s scheme are inaccurate or missing such that their scheme cannot work as claimed. The details of how these flaws damage Chen et al.’s scheme are shown in this paper.