Copyright 2001 Society of Photo-Optical Instrumentation Engineers. This paper was (will be) published in RC21885 and is made available as an electronic reprint [preprint] with permission of SPIE. Single print or electronic copies for personal use only are allowed. Systematic or multiple reproduction, distribution to multiple locations through an electronic listserver or other electronic means, duplication of any material in this paper for a fee or for commericial purposes, or modification of the content of the pater are all prohibited. By choosing to view or print this document, you agree to all the provisions of the copyright law protecting it.
Recently, a number of authentication schemes have been proposed for multimedia data such as images and sound data. They include both label based systems and semifragile watermarks. The main requirement for such authentication systems is that minor modifications such as lossy
compression which do not alter the content of the data preserve the authenticity of the data, whereas modifications which do modify the content render the data not authentic. These schemes can be classified into two main classes depending on the model of image authentication they are based on. One of the purposes of this paper is to look at some of the advantages and disadvantages of these image authentication schemes and their relationship with fundamental limitations of the underlying model of image authentication. In particular, we study feature-based algorithms which generate an authentication tag based on some inherent features in the image such as the location of edges. The main disadvantage of most proposed feature-based algorithms is that similar images generate similar features, and therefore it is possible for a forger to generate dissimilar images that have the same features. On the other hand, the class of hash-based algorithms utilizes a cryptographic hash function or a digital signature scheme to reduce the data and generate an authentication tag. It inherits the security of digital signatures to thwart forgery attacks. The main disadvantage of hash-based algorithms is that the image needs to be modified in order to be made authenticatable. The amount of
modification is on the order of the noise the image can tolerate before it is rendered inauthentic.
The other purpose of this paper is to propose a multimedia authentication scheme which combines some of the best features of both classes of algorithms. The proposed scheme utilizes cryptographic hash functions and digital signature schemes and the data does not need to be
modified in order to be made authenticatable. Several applications including the authentication of images on CD-ROM and handwritten documents will be discussed.
By: Chai Wah Wu
Published in: SPIE Proceedings, volume 4314, (no ), pages 241-52 in 2001
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