Proof of existence, integrity, and ownership contract

Nowadays, enterprises are using electronic signature solutions to sign agreements. However, the details of such files are stored in databases that can be changed easily, so they cannot be trusted for auditing purposes. Blockchain can solve this issue by integrating blockchain as a solution for these electronic signature systems.

Let's write a Solidity contract that can prove file ownership without revealing the actual file. It can prove that the file existed at a particular time and check for file integrity.

Enterprises can use this solution to store a hash of their agreements on blockchain. The advantage of doing this on blockchains is that the agreement date/time, the actual terms of the agreement, and so on can be proven.

We will achieve proof of ownership by storing the hash of the file and the owner's name as pairs. The owner can be the enterprise that created the agreement. On the other hand, we will achieve proof of existence by storing...