WASHINGTON, Jan. 26 (Xinhua) -- Researchers at the University of Copenhagen have developed one of the world's most secure marking systems for combatting pirated goods, using a combination of colored sand grains with rare earths.

The study, published in Science Advances on Friday, develops a system that researchers call "the safest in the world" when it comes to clamping down on all types of pirate manufacturing.

"The probability of two products having the same 'fingerprints' is so minuscule, that in practice, it can only be described as non-existent," said the team leader Thomas Just Sorensen. "It corresponds to a one out of an enormous number composed of a 6 followed by 104 zeros."

Researchers commingled three tubs of sand grains, each of which are added with three rare earths, europium, terbium and dysprosium and pulls a part of them to attach those commingled grains to products.

Since each rare earth lights up when exposed to a specific wavelength of light, so those combinations are unique. Measuring only a few millimeters, they can be impregnated into leather, embedded into glass or milled into metal, the study shows.

Then, producers can take pictures of the imprints at individual wavelengths and store them in a database. When a customer would like to know whether a product is genuine or not, its scanned image can be compared with that in the database.

Researchers estimate that the cost of marking products will be modest, but additional expenses from the data systems have yet to be fully estimated.