A study of the interaction of paper substrates on printed forensic imaging

At the microscopic level, printing on a substrate exhibits imperfections that can be used as a unique identifier for labels, documents and other printed items. In previous work, we have demonstrated using these minute imperfections around a simple forensic mark such as a single printed character for robust authentication of the character with a low cost (and mobile) system. This approach allows for product authentication even when there is only minimal printing (e.g. on a small label or medallion), supporting a variety of secure document workflows. In this paper, we present an investigation on the influence that the substrate type has on the imperfections of the printing process that are used to derive the character 'signature'. We also make a comparison between two printing processes, dry electro photographic process (laser) and (thermal) inkjet. Understanding the sensitivity of our methods to these factors is important so that we know the limitations of the approach for document forensics.