As the interconnected networks for instant transaction prevail and the power of digital multimedia processing tools for perfect duplication and manipulation increases, forgery and impersonation become major concerns of the information era. This chapter is intended to disseminate the concept of digital watermarking for multimedia authentication. Issues and challenges, such as security, resolution of tamper localization, and embedding distortion, of this technical area are explained first. Three main categories of watermarking approaches, namely fragile, semi-fragile, and reversible schemes, to the issues and challenges are then presented. Merits and limitations of specific schemes of each category are also reviewed and compared.
