<title>Distortion-bounded authentication techniques</title>

Abstract

Authentication techniques provide a means of ensuring the integrity of a message. The recent proliferation of multimedia content has led to a need for developing authentication mechanisms. Although, authentication techniques have been studied for many decades, multimedia authentication poses some new challenges. Perhaps the key such challenge being the need to authenticate multimedia content as opposed to its representation. In this paper, we review some of the techniques proposed in the literature for multimedia content authentication. We then propose distortion bounded authentication techniques that give hard guarantees on the amount of distortion that will be tolerated before the multimedia object under consideration is deemed unauthentic. The basic idea behind distortion-bounded authentication is simple. Quantization is performed (in feature space) before authentication, thereby restricting image features in a known and deterministic manner. The same quantization is performed prior to verification. Distortions less than half the quantization step size will not affect the verification process and the content will be deemed authentic. The basic framework is simple and can be applied with many different techniques, distortion measures and feature sets. We give examples of distortion-bound authentication techniques using the L1 and L2 norms in pixel domain.