A Perceptual Image Hashing Algorithm for Hybrid Document Security

In order to create an automatic document security system one needs to secure the textual content but also the graphical content of the document. This paper proposes a hashing algorithm capable of securing the graphical parts of paper and digital documents with unprecedented performance and a very small digest. The main challenge for such an algorithm is that of stability, in particular with respect to print and scan noise. We define the generic notion of stability and how to evaluate it. To achieve such performance we use both dense local information and global descriptors. We have tested our method on two datasets totaling nearly 45000 images.