A review of indirect authentication in LEO satellite networks: Three decades of progress

Low Earth Orbit (LEO) satellite networks have become the main differentiator in achieving global connectivity, augmenting terrestrial networks through improved coverage, lower latency, and seamless integration with next-generation technologies such as 5G, IoT, and edge computing. However, the expansion of LEO constellations introduces substantial security challenges, mainly in ensuring authentication under dynamic, resource-constrained conditions. Indirect authentication, where satellites serve as intermediaries rather than authenticators, is the most commonly adopted model due to its lightweight design and operational efficiency. Despite its prevalence, the current body of research lacks a comprehensive and up-to-date review focused exclusively on indirect authentication protocols within LEO environments.This survey addresses that gap by systematically analyzing 69 indirect authentication schemes published within the last three decades. The protocols are analyzed based on architecture, cryptographic design, security features, and performance trade-offs. In addition to tracing the evolution of indirect models, The study also examines emerging approaches, blockchain, quantum-resilient, physical-layer, and Zero Trust authentication, while identifying trends, challenges, and future research directions. By providing a structured and critical review, this work aims to support the design of secure, scalable, and efficient authentication methods tailored to the unique demands of LEO satellite networks.