nx_sha1.nx

sha1.nx -- SHA-1 (FIPS 180-4 §6.1), 160-bit hash. NOT cryptographically safe for new protocols -- SHAttered (2017) produced chosen-prefix collisions; any signature scheme using SHA-1 is considered broken. But SHA-1 remains on the wire: - TLS 1.0/1.1 MAC (legacy handshake interop) - WebSocket handshake (RFC 6455 uses it in Sec-WebSocket-Accept; collision resistance is not relied on here -- just the mixing property, so it's safe in this specific use) - git object IDs (migrating to SHA-256 slowly) - HMAC-SHA1 (still fine; HMAC is collision-agnostic) - OAuth 1.0, PBKDF2, old certificates So we ship it for protocol interop, never for new signatures. Algorithm (FIPS 180-4 §6.1): - Pad: append 1 bit, zero-pad, append 64-bit big-endian length so total length is a multiple of 512 bits. - Process in 512-bit blocks using 80 rounds. - State is 5 words (H0..H4) initialised to the FIPS constants. Invariants: S1 Matches FIPS 180-4 test vectors. S2 Empty input hashes to da39a3ee5e6b4b0d3255bfef95601890afd80709. S3 State mmap'd per call -- no globals. license_tier: INDEPENDENT_REDERIVE genealogy_id: international-research-sources/nist/fips_180_4