Note that the aforementioned robust storage can be easily turned into an authenticated storage. Authenticated storage refers to a storage system where each entity can prove to another that it had stored a given object. Typical examples are court documents that need to be attested (e.g., that they are issued by a given entity) or modifications/updates to legal documents.
Namely, blockchain users are typically equipped with nonrepudiable pub- lic/private key pairs. Since each transaction confirmed in the blockchain is authenticated, users can prove in the aforementioned storage protocol the ownership of object O.
Clearly, the blockchain can also be used to prove data ownership without revealing the actual data. For instance, one can publicly reveal a file digest (e.g., hash) for an object that has been committed in the blockchain and if conflict arises the person can prove that he or she has the data that matches the hash. This is especially useful for contracts, copyrighted material, patents, and so on. For example, one can prove that he or she developed a specific software revision at any given point in time by time-stamping the hash of the revision tree. BTProof  and Proof of Existence  already offer such services by leveraging Bitcoin’s blockchain.
-  In the case of Bitcoin, each public key maps to a unique Bitcoin address.