nx_blake2b.nx

nx_blake2b.nx -- RFC 7693 BLAKE2b-512 hash (variable output length). BLAKE2b is the 64-bit-optimized member of the BLAKE2 family (Aumasson, Neves, Wilcox-O'Hearn, Winnerlein 2013). The substrate brick under nx_argon2id (RFC 9106) and any future nx_blake3 / nx_kangaroo12 work. Per cardinal feedback-bits-up-exceed-never-match: This is the substrate's own BLAKE2b -- not a libsodium binding, not an OpenSSL EVP wrap. The math runs on substrate i64 ops. Per cardinal feedback-no-third-party-trust-native-or-nothing: Validated against RFC 7693 Appendix A KAT byte-exactly. Any change here MUST re-run the KAT smoke. ===== Algorithm summary (RFC 7693 sec 3) ========================= State: 8 x u64 chained hash words h[0..7], initialized to the BLAKE2b IV (= SHA-512 IV: square roots of first 8 primes). Parameter block (8-byte XOR into h[0]): byte 0 : output digest length (1..64) byte 1 : key length (0..64) byte 2 : fanout (1 for sequential) byte 3 : depth (1 for sequential) byte 4-7 : leaf length (0 for sequential) Compression F(h, block, t, last): v[0..7] = h[0..7] v[8..15] = IV[0..7] v[12] ^= t low 64 bits (bytes-so-far including this block) v[13] ^= t high 64 bits (0 in normal usage) v[14] ^= 0xFFFFFFFFFFFFFFFF if last block for r in 0..12: Mix 8 column + 4 diagonal moves per RFC 7693 sec 3.2. h[i] ^= v[i] ^ v[i+8] for i in 0..7 G(v, a, b, c, d, x, y):