1. Context

Humanity is accumulating data at an unprecedented and exponentially increasing rate. The data considered here is that of our family, friends and professional connections, our books, videos and photos, our medical data, that of scientific research, industry and so on. This is sometimes referred to as big data or megadata . And much more is to come: autonomous cars, sensors and other connected objects, remote surveillance, virtual reality, medical deserts compensated by teleconsultation, remote diagnosis and even surgery. By 2025, it is estimated that three quarters of us will be connected, and that we will each interact with data every 18 s on average...