Calypso is an auditable data-management framework that allows decentralize sharing and life-cycle management of private data. It is describe in this paper:

We use Calypso to store private data on the blockchain. DARCs describe the access to this private data. We use it in an example game of rock-paper-scissors in our example mobile application. Our next target is to implement a GDPR compliant data storage with tracking of sensitive data. It will also include transparent disposal of sensitive data.

The implementation of Calypso can be found here: