A Review on Watermarking Techniques for Multimedia Security
To ensure the safety of the analog data, it is enough to store it physically. With the transfer of data to the digital environment, the concept of data security has been moved to a different dimension. The emergence of the Internet brought data security among the most discussed issues. Higher data transfer speed and higher storage capacity of data make more difficult the protection and authentication of digital data including personal and commercial audio, video and image. Concepts such as cryptology, steganography, digital signature and watermarking have been used for data security. In this study, the concept of watermarking which is used for data security is explained. History of watermarking, watermarking methods, watermarking types and watermarking media are mentioned. Watermarking methods are introduced in the spatial and frequency domain. Comparison of methods and performance metrics are described.
We present a system based on a Semantic Web approach to retrieve photos from events, organizations or even related to semantic concepts using context and social information, without require extra annotation work by the publishers. We make use of the knowledge of the system, represented in ontologies and semantic rules, to allow users search using its own terminology.