The Digital Green Certificates Verifier App is responsible for scanning and verifying DGCs using public keys from national backend servers. Offline verification is supported, if the latest public keys are present in the app's key store. Consequently, once up-to-date keys have been downloaded, the verification works without active internet connection.

Details on the Digital Green Certificate itself can be found at the corresponding web page by the EU Commission. Quoting from there:

A Digital Gr