This book constitutes the thoroughly refereed post-conference proceedings of the 7th International Workshop on Digital Watermarking, IWDW 2008, held in Busan, Korea, in November 2008. The 36 regular papers included in the volume were carefully reviewed and selected from 62 submissions. Areas of interest to the conference are mathematical modeling of embedding and detection; information theoretic, stochastic aspects of data hiding; security issues, including attacks and counter-attacks; combination of data hiding and cryptography; optimum watermark detection and reliable recovery; estimation of watermark capacity; channel coding techniques for watermarking; large-scale experimental tests and benchmarking; new statistical and perceptual models of content; reversible data hiding; data hiding in special media; data hiding and authentication; steganography and steganalysis; data forensics; copyright protection, DRM, and forensic watermarking; and visual cryptography.