[logifail]

> But Serbia's system seems flawed, the EU system has all the data encoded in the QR-code, including name, the date the test was performed, the sort of test (PCR or antigen), and the result, plus a digital signature to prevent changing of those fields

(I'm in the EU): I can get a free "gargle" PCR test - either via walk-up test centre or via collect/test-at-home/drop-sample-in-collection box any time I want here, and in both cases there is zero verification that the sample I provide for the test actually came from my mouth.

If you have a friend who is Covid19 positive, it would be trivial to get yourself a positive result.