nx_nishifs_crypt.nx

nx_nishifs_crypt.nx -- ladder C7 (the FS): NATIVE ENCRYPTION AT REST for NishiFS (the last FS core axis). Content-addressed encryption, done honestly: the CID is sha256 over the PLAINTEXT (so integrity-on-read + dedup are preserved), the object is stored as CIPHERTEXT, and reads DECRYPT-then-verify the CID -- so a WRONG KEY yields wrong plaintext -> CID mismatch -> rejected (the integrity check doubles as authentication). Cipher = a SOVEREIGN sha256-keystream (hash-CTR): keystream block_i = sha256(key || nonce || i), XORed into the data; per-object nonce = the plaintext CID (convergent encryption -> same content+key = same ciphertext = dedup preserved). XOR is implemented bitwise (xorb) since it composes only +,&,|,<<,>>. HONEST CAVEATS (no overclaim): (1) a standard AEAD (ChaCha20-Poly1305 / AES-GCM) is the hardening refinement over a hash-CTR stream cipher; (2) convergent encryption has the known confirmation-of-file attack; (3) the key here is a literal for the KAT -- real key mgmt (KDF from a passphrase / hardware) is separate. KAT 6/6: T1 encrypt-at-rest round-trip (right key decrypts); T2 stored bytes are CIPHERTEXT (!= plaintext); T3 wrong key -> AUTH-FAIL (no plaintext leaked); T4 CID over plaintext + dedup (same pt+key -> same store, arena does not grow); T5 tamper ciphertext -> AUTH-FAIL (integrity caught); T6 distinct plaintext -> distinct ciphertext (no keystream reuse). composes nx_sha256 + nx_syscalls. NEVER-BRICK (Rule 26): pure in-memory, writes NOTHING. expect_exit: 0 license_tier: ORIGINAL