The Dutch health ministry is investigating how cybercriminals managed to create a valid CoronaCheck app code in the name of Adolf Hitler.

RTL Nieuws reported that the fake code returned a green ‘negative’ result when scanned with the ‘test for entry’ app, despite using the deceased dictator’s name and giving his birth date as January 1, 1900.

RTL said it had contacted the fraudster, who said he was selling imitation French and Polish QR codes for €300. The apps are valid in the Netherlands under the European Union’s reciprocal scheme.

Officials at the ministry are said to be concerned that hackers may have obtained the ‘private keys’ used by the makers of digital pass codes, which could mean all QR codes issued by the affected country have to be invalidated.

It is not the first time the ‘test for entry’ system, used to prove people have been vaccinated or tested negative before they enter indoor venues, has been compromised. Last month a 20-year-old man from Alphen aan den Rijn was arrested and several staff at local health service (GGD) offices were suspended from duty on suspicion of falsifying vaccination codes.