N3PA-STIN: A Novel Three-Party Authentication Protocol for Multi-User Access in Satellite-Terrestrial Integrated Networks

Satellite-Terrestrial Integrated Network (STIN) serves as essential infrastructure for providing seamless global coverage and wireless remote subscription services. However, the inherent heterogeneity, satellite exposure, and the openness of satellite-terrestrial links pose significant security challenges for authentication, such as privacy breaches, eavesdropping, replay attacks, and identity impersonation, as well as scalability issues like dynamic node joining and revocation. Existing authentication protocols suffer from deficiencies in unlinkability, scalability, and resistance to multiple attacks, and often rely on overly optimistic assumptions regarding satellite trustworthiness. Moreover, performance bottlenecks in handling numerous user access authentication requests within short timeframes remain unresolved. To address these challenges, we propose the N3PA-STIN protocol, a novel three-party authentication protocol for multi-user access that ensures mutual trust among users, satellites, and ground stations. The protocol minimizes computational overhead through an efficient batch verification mechanism, and enhances privacy and unlinkability by employing temporary identifiers derived from one-time pseudonyms. Furthermore, the protocol ensures conditional anonymity, enabling accountability while preserving user privacy, and achieves conditional verifiability by restricting the verification of authentication messages exclusively to registered nodes. A domain key update mechanism based on the Chinese Remainder Theorem (CRT) supports dynamic node management, effectively addressing the scalability challenges in heterogeneous networks. Security and performance analyses demonstrate that the N3PA-STIN protocol meets the security requirements and minimizes both computational and communication overhead, making it a practical and effective solution for STIN.