A first thing is to find ways to control how data can be used. Researchers at the Massachusetts Institute of Technology Media Lab are developing a cloud-computing platform called Enigma to let individuals share their data, while controlling how it can be used. Suppose an insurance company wants to use people's mobile phone data to assess risks more accurately, which could reduce client premiums. Both company and clients could benefit, but if individuals just hand over their data, the company might sell it or use it for other purposes. The system being developed -- based in bitcoin technology -- would let individuals retain ownership of their data, follow how it is used and instantly opt-out.