A Secure and Efficient ECC-Based User-to-User Authentication and Key Agreement Protocol for Smart Grid

Smart grid environments increasingly require secure user-to-user (U2U) communication for decentralized applications such as peer-to-peer energy trading and electric vehicle energy exchange. However, many existing authentication and key agreement schemes rely on centralized entities during authentication or provide insufficient protection against impersonation, insider, and ephemeral secret leakage (ESL) attacks. To address these limitations, this paper proposes an Elliptic Curve Cryptography (ECC)-based secure U2U authentication and key agreement protocol for smart grid environments. The proposed protocol employs ECDH-based session key establishment and Schnorr verification to enable mutual authentication without directly exposing long-term credentials. In addition, the protocol provides user anonymity and unlinkability by using session-dependent identity protection mechanisms. Security analysis demonstrates that the proposed scheme can resist various attacks, including impersonation, replay, denial-of-service, privileged insider, stolen device, and ESL attacks. Furthermore, simulation-based comparative analysis shows that the proposed protocol achieves stronger security features than several existing schemes, although it incurs moderately higher computational and communication costs due to additional elliptic curve operations and verification parameters.