Talk given in 2024 at Devoxx Belgium, the biggest vendor-independent Java conference in the world which takes place in one of the biggest European cinema complexes, the Kinepolis, located in Antwerp, Belgium.

Masks are being used for thousands of years, all across the physical world, for reasons such as physical protection, rituals and hiding the identity of the bearer. Physical masks are probably the oldest privacy protection technology.

When writing and printing, authors of books and articles used pseudonyms to hide their identity. Voltaire, Lenin and Banksy are well known pseudonyms: modern, written versions of the physical mask. In the digital age we now replace citizens’ identifiers by unique codes – having remarkably powerful and even counter-intuitive properties when based on cryptography.

The public sector has two seemingly contradictory tasks: protecting citizens and their privacy, while maximizing value and efficiency for individuals and society. So should we minimize or maximize data?

The Belgian public sector increasingly adopts cryptography for pseudonymization – a crucial, and yet sufficiently practical element in realizing the seemingly impossible.

In this talk, Kristof introduces three practical cryptographic systems for pseudonymization. He has designed them, based on specific needs within social security and healthcare. If you live in Belgium, your personal data is probably already protected by one of these systems, today.