This is out of educational interest. There seems to be some interesting combination of algorithms going on, such as base54, CBOR, QR, JSON, etc.

Has the EU pass tech and so forth been discussed on /sci/, yet?

https://github.com/ehn-dcc-development/hcert-spec
https://github.com/eu-digital-green-certificates
https://www.schengenvisainfo.com/news/eu-investigates-hacking-of-covid-digital-certificates-gateway-after-adolf-hitler-certificate-was-generated/