FB-ASC+: Improved Fog-Blockchain Assisted Certificateless Aggregate Signcryption Scheme

Smart grids enable two-way communication between control centers and smart meters. However, this capability introduces security and privacy risks and has consequently prompted extensive research. Liu et al. proposed a fog-blockchain-assisted certificateless aggregate signcryption (FB-ASC) scheme to achieve confidentiality and unforgeability in smart grids. Our research demonstrates that their signcryption design achieves neither confidentiality nor unforgeability, and we show that the supporting lemmas in their paper do not hold. Under the same system models, we presented effective attacks on their scheme and consequently proposed the FB-ASC+ scheme that provides provable security guarantees against the aforementioned attacks. Comparison results further illustrate its performance advantages over pairing-based alternatives in typical smart-grid scenarios.