This is a very interesting development. Encryption generally would solve a lot of problems around data sovereignty. So, encrypting the data, keeping the key and moving the data to the public cloud could basically address a lot of the risks. Today, it comes with a high price as the data which resides encrypted in the Cloud cannot be index (therefore is not searchable) nor can any operation be conducted.
The solution is homomorphic encryption, where a lot of research is done but it is still too slow. People at Microsoft Research now took a now angle on it: They took, what is already here and looked at the scenarios, which are already possible today.
The following article gives an interesting overview, what would be possible based on today’s research: A Cloud that Can't Leak