EP20 Hot Issue - Digital vaccination certificate

Covid-19 vaccination certificates in the form of physical cards are already being sold via online marketplaces. A doctor to question how the authorities would be able to ascertain the authenticity of such cards. Aug 10, digital certificates “confirming” that an individual has been fully vaccinated against Covid-19 vaccine are being sold by irresponsible parties via social media. If the public is allowed to make a vaccine certificate identity card or print the vaccination certificate themselves, how can the authorities know between the genuine and the fake?