US Patent 7533905 - Anti-counterfeiting nanostructure

http://www.freepatentsonline.com/7533905.html

This patent from HP teaches a nanostructured mating arrangement designed to prevent the use of counterfeit inkjet print cartridges. Claim 1 reads:

1. An anti-counterfeiting system, comprising:

a first structure having a first plurality of three-dimensional nanostructures each having a height dimension less than a wavelength of visible light;

a second structure having a second plurality of three-dimensional nanostructures each having a height dimension less than a wavelength of visible light, the second plurality configured to couple with the first plurality; and

an alignment mechanism, operable to align the first structure to the second structure and establish proximate contact between the first and second pluralities of three-dimensional nanostructures;

wherein the first plurality of three-dimensional nanostructures encodes a first part of an authentication key, and wherein the second plurality of nanostructures encodes a second part of the authentication key, the authentication key including pre-determined elements and interaction modalities.