During a speech at the club's 31st annual convention on Saturday, Jan Krissler, a so-called ethical hacker and researcher, said an image of the thumbprint would soon be posted on the internet, DPA reported.

Krissler went on to say that obtaining the copy did not require an object that the defence minister had touched.

He added that commercially available software called VeriFinger was utilized along with a close-up picture of von der Leyen’s thumb, which was obtained during a news conference in October.

After showing a partial picture of the defense minister’s thumbprint, the hacker went on to say the missing parts of the image were completed using photographs taken from different angles.

Back in 2008, Krissler published the fingerprint of Germany's then interior minister, Wolfgang Schaeuble.

According to German news website Zeit Online, Krissler and another hacker Tobias Fiebig have conducted research into the limitations of biometric security systems for the Technical University of Berlin.

Security systems are ever increasingly using biometrics which require fingerprints or iris scans for authentication.