This PR establishes a formal, side-channel-aware naming convention for secret function arguments. It updates CONTRIBUTING.md to require the sec prefix for any function arguments processed in constant time. Relevant secret arguments in the API (like key32, nonce32, tweak32, and aux_rand32) have been renamed to seckey32, secnonce32, sectweak32, and aux_secrand32. Arguments that are intentionally not constant-time (such as public tweaks) remain unchanged, clearly distinguishing their behavior. All underlying source files, headers, and tests have been updated and fully tested to ensure no regressions.