Document security method utilizing microdrop combinatorics, ink set and ink composition used therein, and product formed

A printing method for producing a printed object that is resistant to counterfeiting, comprising the steps of:

• providing a set of ink components comprising a plurality of different ink components having respective spectral responses, whereby at least two of the different ink components can be mixed together to provide an ink composition, the at least two of the different ink components, when mixed together, providing a spectral response of the mixture which deviates from a predicted spectral response when linearly additively combining the respective spectral responses of the at least two of the different ink components;
• selecting said at least two of the different ink components of the set of ink components;
• mixing the selected at least two of the different ink components, so as to provide the ink composition;
• and
• applying said ink composition to a substrate which is a substrate of an object that needs protection against counterfeiting, thereby forming the printed object.

A method of verifying authenticity of an object, comprising the steps of:

• a) providing an object with at least one marking, having a corresponding spectral response, at a first location of the object, the object being an object needing protection against counterfeiting;
• b) providing a template representing a spectral response of at least one authentic marking, said at least one authentic marking each being a marking formed from ink components, the at least one authentic marking each having a spectral response which deviates from a predicted spectral response when linearly additively combining respective spectral responses of the ink components of the at least one authentic marking;
• and
• c) comparing the object and the template to determine whether spectral responses of the at least one marking on the object and the at least one authentic marking of the template match, whereby, if the markings substantially match, the object is verified to be authentic.