A Dutch judge has ruled that details of how to copy MIFARE Classic cards used on London’s transport network can be published.

The ruling follows a recent injunction taken out by NXP which sought to prevent researchers at Radboud University in the Netherlands from revealing their findings at the European Computer Security Conference - Esorics – in Spain in October.

Researchers at the university discovered the shortcomings of the chip in March 2008. The university says it immediately and confidentially informed the Dutch government as well as NXP of the results of the independent research on the Mifare Classic Chip.

The court in Arnhem ruled that publishing this scientific article falls under the principle of freedom of expression and that in a democratic society it is of great importance that the results of scientific research can be published.

Christophe Duverne, senior vice president and general manager of the identification business at NXP, told Reuters it would take months or even years for some users of the chip to adapt their systems, and that the publication was thus different from software hacks for which manufacturers can issue a patch much more quickly.

He said: "We don´t mind them publishing the effects of what they have discovered to inform society, I think this is absolutely fine.But disclosing things in detail including the algorithm … is not going to benefit society, it will create damage to society.”