Currently when buying and selling digital assets, there is no way to truly secure and validate ownership in a digital asset or verify a transaction in a decentralized (trustless), public manner.
For example, say you sell a WordPress plugin to someone. What prevents them from sharing this plugin with someone else who could use it without paying any licensing fee? Through PMES, digital assets are claimed by the owner (recorded on the blockchain as an append-only public record). Then these assets are then sold using cryptocurrency and accessed via a password key.