The smart grid (SG) plays an increasingly essential role in people’s daily lives. However, cross-domain energy-sharing security and efficiency have become important, along with the diversity and remoteness of energy resources. This paper first introduces a blockchain-enabled EV-shared charging model with blockchain technology to improve energy management and sharing ability. Then, an identity-based aggregate signature (ID-AS) scheme has been designed to improve the efficiency of signature verification for the large volume of transaction verification in a blockchain-enabled smart grid. Meanwhile, the lattice assumption can enhance the anti-quantum security of the cross-domain energy-sharing processes. The simulation and performance comparison results show that the proposed model and algorithm are more efficient and practical.