Speedcash / SCS already offers solution for this:
VAULT technology allows a user to validate document authenticity without disclosure of the document data by storing document hash on the SpeedCash blockchain.
Concretely SpeedCash VAULT allows SpeedCash holders to publish file validation fingerprints (hashes of files) over the blockchain. The content of the document itself is not published, allowing you to preserve its privacy. This has obvious benefits as all blocks in the SpeedCash network are marked with a timestamp, the time identifier impossible to falsify. Such publication proves that you owned the document at the specified time and can be used as legal proof of the ownership. It also allows users to verify a file’s integrity over time, for example if the hash of the file changes or the file has been altered or corrupted.
Combined with
Trusted Signature (match of SpeedCash wallet address and the person's name, nick name or company name) this feature allows the authors to protect their right over time.
www.scash.mlhttps://www.scash.ml/speedcash-vault/https://www.scash.ml/trusted-signatures/https://t.me/speedcashcoin