a method and system for characterizing blocks of printed material . a digital image of printed material , such as an address block , on an object is obtained , and the image is processed to abstract characterizing information descriptive aspects of the other printed material . the characterizing information is combined with other information , such as postal information and the combined information is then cryptographically authenticated with a digital signature or the like . an indicium representative of the authenticated information is then printed on the object . the object &# 39 ; s relationship to the indicium can be verified by regenerating the characterizing information from the other printed material and comparing the regenerated characterizing information with characterizing information recovered from the indicium . thus , copies of the indicium cannot easily be used , without detection , on other objects which do not include the other printed material . a combination of algorithms is selected from a predetermined group of characterizing algorithms by determining an estimate for the robustness of each algorithm and selecting a combination having high overall robustness .