nx_sha256.nx

sha256.nx -- SHA-256 in pure NishiLang (Phase G9, FIPS 180-4). Canonical: this is the substrate-wide canonical SHA-256 implementation per [[feedback-no-tool-proliferation-bit-level]]. HMAC-SHA256 / HKDF-SHA256 / DRBG-SHA256 etc. compose THIS file's sha256 primitive; they're distinct primitives (different specs: FIPS 198-1 HMAC, RFC 5869 HKDF, NIST SP 800-90A DRBG) but all share THIS sha256 as their SHA-256 backbone. Re-implementing the SHA-256 K-table or round function inline is refused. license_tier: INDEPENDENT_REDERIVE genealogy_id: international-research-sources/nist/fips_180_4 Used for: content-addressed build artifacts (F6), session tokens (rand.nx + sha256 = HMAC), TLS 1.3 handshake (G15), Git-style object addressing, reproducible-build attestation. Implementation follows FIPS 180-4 section 6.2 exactly -- no precomputed tables beyond the standard K[0..63] round constants. Pure i64 arithmetic; all 32-bit ops masked with 0xFFFFFFFF. API: sha256_init(*ctx) — reset a fresh Sha256 context sha256_update(*ctx, *u8 bytes, len) — feed input chunks sha256_final(*ctx, *u8 out32) — write 32-byte digest sha256_digest(*u8 bytes, len, *u8 out32) — one-shot convenience The context is ~128 bytes: 8 words of hash state + 64-byte partial block buffer + 8-byte length counter + an index. Caller allocates (stack or heap) and passes pointer. nx_safety_envelope: (schema: nishi-library/seeds/safety-critical-standards.toml) intended_use: "SHA-256 cryptographic hash -- HMAC + HKDF + content-addressed storage + digital signatures + Wheeler-DDC integrity chain" sil_target: SIL3 (integrity primitive; collision or preimage attack = signature forgery) asil_target: QM dal_target: DAL B iec_62304_class: B