This patent document discloses physical documents including metameric ink pairs. One claim recites a document comprising: a first surface; a second surface, in which the first surface comprises a first set of print structures and a second set of print structures, in which the first set of print structures and the second set of print structures collective convey an encoded signal discernable from optical scan data representing at least a first portion of the first surface, in which the first set of print structures is provided on the first surface with a first ink and the second set of print structures is provided on the first surface with a second, different ink, and in which the first ink and the second, different ink comprise a metameric pair. Of course, other claims and combinations are described as well.

A concentric CRR sensor is claimed that is used as a form of currency verification in order to combat counterfeiting currency. The system comprises applying sets of concentric CRR printed with transparent conductive ink. In one embodiment, using the CRR as a passive RFID tag, changing the ring's radii, inner or outer, and in turn, created more encryption, and thereby prevents currency counterfeiting. In one or more embodiments, the serial number of the currency bill is used as a guideline to a selection algorithm to determine the size of the radii.

The invention relates to a method for securing a document including a visual element, carried out by a processing unit comprising processing means, the method comprising generation, from the visual element, of a reference security datum, and storage of the reference security datum,

wherein the reference security datum is generated by means of an algorithm configured so as to generate: for any image acquired from the visual element, a security datum whereof the differences relative to the reference security datum are less than a determined threshold, and for any image acquired on a different visual element, a security datum whereof the differences relative to the reference security datum are greater than said threshold.

A document is received by a first computer system from a second computer system. The document is received through a network. A document level security code is received by the first computer system through a second network. A content level security code is received by the first computer system and through the second network. A first validation operation is performed by the first computer system. The performance is based on the document level security code. The first computer system determines the document is an altered document. The determination is based on the performance of the first validation operation. A second validation operation is executed on the altered document. The second validation operation is executed by the first computer system and in response to the determination. An alteration status of the document is detected by the first computer and based on the second validation operation.

The invention relates to a workpiece with a manufactured surface structure that forms a decorative pattern, wherein an optically detectable coding is integrated in a reference area of the surface structure of the workpiece. The invention further provides a method for manufacturing a workpiece with such a coding or marking. Such a workpiece can, for example, be a workpiece or an object used in the field of furniture or components industry, in particular a piece of furniture or a part of a piece of furniture.

A method of marking an article for authentication, the comprising the steps of applying an identification mark to an article, said mark comprising an array of varying sized markings, where the combination of the shape, the spatial distribution and the varying sizes of the markings imparts a distinctiveness to the identification mark recording the identification mark in a database and associating information relating to the article with the identification mark in the database, wherein comparison of the identification mark on the article and the database enables the identification mark to be associated with the information relating to the article on the database.

A concentric CRR sensor is claimed that is used as a form of currency verification in order to combat counterfeiting currency. The system comprises applying sets of concentric CRR printed with transparent conductive ink. In one embodiment, using the CRR as a passive RFID tag, changing the ring's radii, inner or outer, and in turn, created more encryption, and thereby prevents currency counterfeiting. In one or more embodiments, the serial number of the currency bill is used as a guideline to a selection algorithm to determine the size of the radii.

A document is received by a first computer system from a second computer system. The document is received through a network. A document level security code is received by the first computer system through a second network. A content level security code is received by the first computer system and through the second network. A first validation operation is performed by the first computer system. The performance is based on the document level security code. The first computer system determines the document is an altered document. The determination is based on the performance of the first validation operation. A second validation operation is executed on the altered document. The second validation operation is executed by the first computer system and in response to the determination. An alteration status of the document is detected by the first computer and based on the second validation operation.

A method of marking an article for authentication, the comprising the steps of applying an identification mark to an article, said mark comprising an array of varying sized markings, where the combination of the shape, the spatial distribution and the varying sizes of the markings imparts a distinctiveness to the identification mark recording the identification mark in a database and associating information relating to the article with the identification mark in the database, wherein comparison of the identification mark on the article and the database enables the identification mark to be associated with the information relating to the article on the database.

An authentication system and associated method including a substrate including one or more doped inclusions disposed in or on the substrate at one or more portions of the substrate such that electromagnetic radiation absorption and reflectance varies between a portion of the substrate in which a doped inclusion is disposed and a portion of the substrate in which no doped inclusion is disposed, and a detector including an electromagnetic radiation source configured to irradiate the substrate with electromagnetic radiation at multiple wavelengths and an imaging system configured to acquire multiple images of the substrate subjected to irradiation.