Images via the PaperSpeckle datasheet
Forged documents have tricked people for ages. In modern times, document counterfeiting is running rampant in developing countries. Another issue, the countries which have the problem cannot afford the laser scanning equipment that is currently being used to battle the problem. However, New York University has devised an inexpensive solution using cell phones, a microscope, and secret codes that might just be the solution.
The tech is called PaperSpeckle. Developed by Lakshminarayanan Subramanian as his team, the system encoded patterns using Gabor transforms, the same in iris and fingerprint scanners. A unique code is produced, and up to 10^30 different "speckle patterns" can be created. PaperSpeckle's processing software runs on an Android phone and uses a USB microscope. The whole setup could cost sub $100 USB for many people.
In addition to the speckle pattern, a QR code (quick response, matrix barcode) can be generated using the system's software. On a document, the QR code can then direct to an online database or further reading. Although the QR code could be easily copied to another page, the speckle pattern will not match.
I am going to suggest some ways to beat the speckle pattern. First, bribe the authorities, which is the bigger issue anyway. Another, modify the phone or microscope scanner to report the necessary codes. My last idea, use the same equipment to print the proper code. If a forged document is worth enough, the protection will be defeated.
Cabe