[dcolkitt]

For vaccination passports, I don’t think you even need a database. Public key signatures work fine. “John Smith is officially vaccinated. Love, Cook County Health Department”. No persistent service even necessary. John can just keep that QR code on his phone.

Blockchain or trusted database authority is only necessary when there’s the risk of double spend. Like I try to sell my house to two different people at the same time. With vaccine passports there’s no risk. Either you’re vaccinated or not.

[yrro]

You need a service that verifiers can query to determine if the signature has been revoked too...