The present disclosure relates generally to physical object authentication. In some embodiments, methods and apparatus relate to physical object authentication through comparison of randomly or pseudo-randomly occurring features with expected features. In some cases digital watermark or other indicia is used to convey the expected features. Of course, other combinations, embodiments and features are disclosed.

Disclosed is a device for encoding information written on a readable surface, the device including a device housing containing at least one ink reservoir, an ink dispensing tip in communication with said at least one ink reservoir; and ink stored in the at least one ink reservoir and configured to flow from the ink dispensing tip, the ink being encodable to include supplemental encoded information, the supplemental encoded information being detectable by at least one detecting sensor when dispensed on the readable surface, wherein the readable surface is any surface that will accept the ink.

Disclosed is a device for encoding information written on a readable surface, the device including a device housing containing at least one ink reservoir, an ink dispensing tip in communication with said at least one ink reservoir; and ink stored in the at least one ink reservoir and configured to flow from the ink dispensing tip, the ink being encodable to include supplemental encoded information, the supplemental encoded information being detectable by at least one detecting sensor when dispensed on the readable surface, wherein the readable surface is any surface that will accept the ink.

A method for verifying the authenticity of a security document by means of a camera-equipped cellphone comprises steps of acquiring a transmission mode image and a reflection mode image of the security document. Transmitted light through a plurality of perforations in a substrate of the security document is evaluated by means of the cellphone. Then, a relative positioning of the perforations with respect to a printed security features is determined, and the security document is considered authentic if the determined positions and the acquired images substantially correspond to pre-stored templates for the security document. The perforations are structured such that they are not visible to the naked eye of a human observer which makes it harder to counterfeit the security document.

The application discloses printed objects including encoded information, and methods, apparatus and systems for authenticating such printed objects. Some such objects, methods and apparatus involve data hiding and/or encoded signals.