One excellent use case for Blockchains is digital stamping. Imagine it like a digital notary service, but contrary to a traditional notary service you don’t need a trustworthy third party. The blockchain itself provides all the characteristics of a trusted third party: it facilitates secure online transactions, it is a decentralized and distributed network, and registered transactions cannot be altered retroactively. This allows the participants to verify and audit transactions in an inexpensive manner.
Stamping a file on the blockchain proves that the document existed at that particular point of time. If the user has signed the document before stamping, then he may undeniably claim that the document was in his possession at the time of the stamping. Another advantage is that you can prove the files origin, date, authenticity and integrity, without exposing its contents.