Authentication method of a two dimensional bar code

A method of producing a 2D barcode on an article including a laser markable layer, the 2D barcode including a primary information pattern representing primary information and a secondary information pattern embedded within the 2D barcode, the method comprising:

• laser marking by exposing the laser markable layer with an infrared laser to form the secondary information pattern of the 2D barcode;
• wherein
• the primary information is able to be read by a 2D barcode reader and the secondary information pattern is altered when copied or reproduced and the secondary information pattern consists of elementary sub-cells smaller than 50 μm.