  As governments around the world decide to deploy digital health passports as
a tool to curb the spread of Covid-19, it becomes increasingly important to
consider how these can be constructed with privacy-by-design.
  In this paper we discuss the privacy and security issues of common approaches
for constructing digital health passports. We then show how to construct, and
deploy, secure and private digital health passports, in a simple and efficient
manner. We do so by using a protocol for distributed password-based token
issuance, secret sharing and by leveraging modern smart phones' secure
hardware.
  Our solution only requires a constant amount of asymmetric cryptographic
operations and a single round of communication between the user and the party
verifying the user's digital health passport, and only two rounds between the
user and the server issuing the digital health passport.
