In recent years, we keep hearing that every digital system has to be designed with “Privacy by Design”. It is easy to agree with this idea, but in practice, what does it mean? In this talk, we will discuss different interpretations of this philosophy that allow us to approach the problem from a technical point of view. We will see, through examples, how it is possible to combine technologies designed to enhance privacy (Privacy Enhancing Technologies) into systems that allow complex functionalities without the need to collect and process data. We will end the talk by discussing challenges that arise when applying this design methodology and that may prevent the widespread deployment of these technologies.