Computer implemented method for generating a hash value (110) is disclosed, the method comprises the following steps: i) Providing a first digital RGB image (112) having first RGB colors of a physical object (114); ii) Combining first transaction data (116) and the first digital RGB image (112), thereby generating a second RGB image (118) having second RGB colors; iii) Converting (128) color values of the second RGB image (118) from RGB color space (130) to a secondary color space (132) having at least four primary colors and determining (134) a number of respectively colored pixels for each primary color of the secondary color space (132); iv) Generating (136) the hash value (110) by converting the determined number of respectively colored pixels for each primary color of the secondary color space (132) to hexadecimal numerals.