Cryptographic Attribution and Immutable Decryption Provenance for Multi-Recipient Encrypted Document Distribution

Source summary

Develop a document-distribution system in which one encrypted file can produce recipient- and session-specific forensic copies when decrypted. Each copy should remain visually unchanged while carrying an invisible watermark associated with a recipient-signed decryption record. Use NIST-standardized post-quantum algorithms for key exchange and signatures, and a tamper-evident blockchain or distributed ledger for the audit record. The verification function should connect an extracted watermark to the recorded recipient and decryption event through verifiable ledger and signature evidence. All identity, encryption, watermarking, ledger and verification operations must work offline in an air-gapped environment, without cloud key-management services or public blockchains.