A Survey of Astronomical Systems for Cryptographic Entropy Generation

This survey comprehensively catalogs astronomical systems with cryptographic potential, analyzing their entropy characteristics, computational complexity, and suitability for multi-epoch security architectures. We examine solar cycles (11-year sunspot, longer periodicities), lunar cycles (synodic, anomalistic, nodal, saros), planetary conjunctions and aspects, and traditional calendrical systems from multiple civilizations. For each system, we quantify configuration space size, enumerate discrete states, and assess observational verifiability. We compare pure astronomical approaches with hybrid systems combining multiple cycle families. Our analysis reveals that multi-dimensional astronomical configuration spaces can achieve entropy levels of 180-220 bits while maintaining full determinism and external verifiability. This survey provides the empirical foundation for implementing astronomical entropy in next-generation cryptographic systems designed for generational security horizons.