  The current humanitarian health crisis popularized the debate on data
privacy. At the same time, several cities, states, and even countries put the
mandatory presentation of health pass to access services into practice. In this
article, we explore the concepts of self-sovereign identity, blockchain, and
zero-knowledge proofs to propose a solution to the problem of presenting proof
of vaccination. This solution allows users to prove that they are vaccinated
for different pathogens without revealing their identity. The architecture is
loosely coupled, allowing components to be exchanged, which we discuss when we
present the implementation of a working prototype.
