© Springer-Verlag 2003 Robust image authentication using content based compression

Abstract. Image authentication is becoming very important for certifying data integrity. A key issue in image authentica-tion is the design of a compact signature that contains suffi-cient information to detect illegal tampering yet is robust un-der allowable manipulations. In this paper, we recognize that most permissible operations on images are global distortions like low-pass filtering and JPEG compression, whereas illegal data manipulations tend to be localized distortions. To exploit this observation, we propose an image authentication scheme where the signature is the result of an extremely low-bit-rate content-based compression. The content-based compression is guided by a space-variant weighting function whose values are higher in the more important and sensitive region. This spatially dependent weighting function determines a weighted norm that is particularly sensitive to the localized distortions induced by illegal tampering. It also gives a better compact-ness compared to the usual compression schemes that treat every spatial region as being equally important. In our imple-mentation, the weighting function is a multifovea weighted function that resembles the biological foveated vision system. The foveae are salient points determined in the scale-space representation of the image. The desirable properties of mul-tifoveaweighted function in thewavelet domains fit nicely into our scheme. We have implemented our technique and tested its robustness and sensitivity for several manipulations