UASCF Base-5 (Quinary): Design, Adversarial Self-Testing, and Defect Disclosure for a 5^1024-Keyspace Symmetric Cipher
S Ravichandran Ayyer · Zenodo (CERN European Organization for Nuclear Research) · 2026
This paper documents the complete design and adversarial self-testing history of UASCF Base-5, a new symmetric cipher operating on a balanced quinary (base-5) digit domain with a 5^1024 keyspace. Unlike prior UASCF variants, this design was developed collaboratively and tested at every construction stage rather than only at completion: a generic cryptanalysis attack toolkit (brute-force, algebraic affine-collapse, differential, and linear modules) was built and validated against positive and negative controls before the cipher itself was written, then applied to each of six block/key combination models (single/multiple character or block, under single/multiple keys), followed by avalanche, Shannon entropy, NIST SP 800-22, and IND-CPA/IND-CCA adversarial proxy testing. This process surfaced four real, disclosed defects — a deterministic-encryption weakness (100% distinguishing accuracy), a plaintext-leakage bug in an early sender/receiver utility, a directional avalanche-measurement artifact, and a bit-serialization bias that caused five spurious NIST test failures — each diagnosed to its root cause and corrected, with before/after results reported for all four. The final construction passes all twelve test vectors, the full NIST SP 800-22 core battery, and both IND-CPA and IND-CCA proxy checks. This paper also records the design rationale behind the choices made before any code was written: why base-5 was selected over binary or ternary, why a mixed-radix construction was considered and rejected, why a published (ARX) mathematical foundation was chosen over inventing a new one, and why the claimed novelty rests on the digit domain and key-chaining scheme rather than on undisclosed mathematics. A complementary, first-line-agnostic second-line layer is also documented: an initial single-bit length-encoding proposal was proven information-theoretically infeasible, redirected to a sound bucketed-padding design analogous to TLS/Tor traffic-analysis defenses, and, after a further disclosed cleartext-metadata defect was found and fixed, verified end-to-end on a physical Android device. Following editorial review, mod-5-native differential and linear cryptanalysis modules were also built, validated against a negative control (surfacing and fixing three further defects in the validation process itself), and applied to the real cipher, finding no structure at the tested, disclosed scope.