nx_doc_seal.nx

nx_doc_seal.nx -- LEGAL RUNG D5: tamper-evident e-signature SEAL. module: nishi-core.legal.doc_seal capability: LEGAL_ESIGN_SEAL Produces a non-repudiable, tamper-evident seal binding {document hash + signer identity + timestamp + the D0 legal regime/verdict} under a REAL RFC 8032 Ed25519 signature (not the V1 nx_sign_facade stand-in, which is explicitly non-cryptographic). This is the "DocuSign but better" core: 1. NEVER SEAL A VOID INSTRUMENT -- nx_seal_create FIRST runs the D0 compliance verdict (nx_legal_compliance) and REFUSES to produce any signature unless the verdict is VALID. The Rule-26 legal invariant is thus carried into the signing layer: you physically cannot e-seal a will that would be legally void. A generic e-sign product signs first and asks never; this one cannot. 2. CANONICAL RECORD -- a deterministic serialization binds the document hash, signer, timestamp, regime and verdict, so the signature commits to the FULL legal validity context, not just "someone clicked sign". 3. TAMPER-EVIDENT -- nx_seal_verify recomputes nothing it isn't given; any single-byte change to the canonical record (document hash, signer, regime, ...) breaks the Ed25519 verification (proven in the gate). Composes: nx_legal_compliance (D0 verdict), the ed25519 RFC-8032 chain (real signature). Distinct from nx_sign_facade because: that is a non- cryptographic V1 stand-in; a legal signature needs real Ed25519. license_tier: ORIGINAL lineage_id: nishi_doc_seal_d5