Since the mid 1990s, data hiding has been proposed as an enabling technology for securing multimedia communication, and is now used in various applications including broadcast monitoring, movie fingerprinting, steganography, video indexing and retrieval, and image authentication. Data hiding and cryptographic techniques are often combined to complement each other, thus triggering the development of a new research field in multimedia security. Two related disciplines, steganalysis and data forensics, are also increasingly attracting researchers and forming another new research field in multimedia security. This journal, LNCS Transactions on Data Hiding and Multimedia Security, aims to be a forum for all researchers in these emerging fields, publishing both original and archival research results. This inaugural issue contains five papers dealing with a wide range of topics related to multimedia security. The first paper deals with evaluation criteria for the performance of audio watermarking algorithms. The second provides a survey of problems related to watermark security. The third discusses practical implementations of zero-knowledge watermark detectors and proposes efficient solutions for correlation-based detectors. The fourth introduces the concept of Personal Entertainment Domains (PED) in Digital Rights Management (DRM) schemes. The fifth reports on the use of fusion techniques to improve the detection accuracy of steganalysis.