1. A method for selecting a characterizing algorithm for generating a characterizing information descriptor for a selected block of printed material, where said printed material is to be scanned from an object and compared with said characterizing information descriptor at a location distant from where said block is printed, said method comprising the steps of: a) printing said block on an object; b) applying each algorithm from a predetermined set of characterizing algorithms to a pristine image of said block of printed material to generate a plurality of corresponding first characterizing information descriptors for said block; c) determining estimates of robustness, with respect to said block of printed material, for each of said algorithms in said set to determine which of said characterizing algorithms is most robust; and d) selecting a descriptor generated by said algorithm and being so determined to be most robust be used at said distant location.