Academics have developed an anti-counterfeit system that uses QR codes printed with invisible ink.
Researchers from the University of South Dakota are able to print the codes, which can contain vastly more information than a standard barcode, using nanoparticles. A laser is required to display the code, which can then be decoded using a regular smartphone.
This is more than security through obscurity, though. Jeevan Meruga, who led the study, said, "We can take the level of security from covert to forensic by simply adding a microscopic message in the QR code... which then requires a microscope to read [it]."
The video below describes the process in more detail.