Yeah it uses cryptographic signing, but fails at the human level when the checker doesn't use the app to check it and doesn't check the holder's ID. But there

Yeah it uses cryptographic signing, but fails at the human level when the checker doesn't use the app to check it and doesn't check the holder's ID. But there were reports that some Germans were selling the certificates on the "dark web" (i.e. you have to know the WhatsApp number of the seller), and are working with rogue pharmacy employees to issue valid certificates...