Let’s say we came up with an amazing new tech buzzword, “3D printing artificial intelligence on the blockchain.” We wanted to prove that we came up with it before some date, but we don’t yet want to reveal the buzzword to the public.
How do we do this in a way that everyone trusts? Well, by combining hash functions and the trustless blockchain! We store a hash of our document onto the blockchain.
By doing so, we can prove to everyone at any later date that we were the ones who included that hash on the blockchain, and that our information has not been changed.
By doing so, we have now “proved the existence” of some piece of information at some point in time.
With Proof-of-Existence, we leverage both the public auditability and immutability of the blockchain.
With a blockchain, we can cryptographically prove commitment to some particular value.
This is nothing more than a record-keeping use case, and there are several which fall under this category.
One of these use cases is document ownership.
We can prove that we own some document at some time through a commitment scheme: hash the document with some random number, then you have your hash commitment.
Reveal the inputs later to prove your ownership.
In addition, there’s the opportunity to implement a decentralized DNS system.
“DNS” stands for “Domain Name System,” and its one purpose is to associate URLs with IP addresses.
Our browsers look to trusted DNS servers to provide this service, but why not put this service on a trustless database? In a smart contract, we can easily design a scheme that creates associations between names and values.
We’ll expand on how we take advantage of these properties in the Advanced Use Cases section.