Proof of ownership or proof of existence is a technique that can be used by anyone via the Bitcoin Cash protocol in order to certify the integrity of a variety of proofs. Our last Guide covered the basics on how a person can prove ownership of a specific BCH address and tether a unique message and digital signature to the address as well.
However, there are other methods available that allow people to record various things like a document or file. The BCH chain allows you to add raw data to a transaction using an opcode called OP_Return. Our website hosts a service called Notary.Bitcoin.com that allows people to tether the hash of a signature and file within the blockchain’s recorded data. Similarly to how the private key allows someone to prove ownership of an address, a private key can also correspond with the owner’s signature and the hash of the file held in the BCH blockchain.