Different Digital Watermarking Techniques for Secure Data Transmission

Watermarking is a technique for labelling digital pictures by hiding secret information in the images. A digital watermark is a kind of marker covertly embedded in a noise tolerant signalsuch as audio or image data. It is typically used to identify ownership of the copyright of such signal. An original image is decomposed into wavelet coefficients. Then, multi-energy watermarking scheme based on the qualified significant wavelet tree (QSWT) is used to achieve the robustness of the watermarking. Unlike other watermarking techniques that use a single casting energy, QSWTadopts adaptive casting energy in different resolutions.In conventional watermarking schemes certain amount of distortion to the recovered image is acceptable. This does not apply to all applications, particularly in military applications, space and medical imagery etc., loss of a single bit of information from the original image is not acceptable. In reversible watermarking, the embedding process has an additional burden of embedding extra information in the payload that includes the recovery data that is used by the decoder to reconstruct the original image bit by bit. Various lossless watermarking schemes are discussed in this paper. Keywords—Digitalwatermark,DiscreteWavelettransform, Qualified wavelet coefficients.