Hidden-Radix Cryptography and Post-Quantum Cryptography: A Comparative Analysis

A systematic comparison between hidden-radix cryptography (schemes where the numerical base or completion is kept secret) and modern post-quantum cryptography (PQC). Traces the evolution of the hidden-radix concept from a naive classical base-change cipher through large-secret-radix key encapsulation mechanisms (Silent Radix Encryption, SRE) to constructions grounded in p-adic completions and the idelic ring. Contrasts with the five principal PQC families (lattice-based, code-based, hash-based, multivariate, and isogeny-based) across dimensions of security model, hardness assumptions, quantum resistance, key sizes, and practical deployability.