Abstract: Due to increasing popularity of the internet use of digital multimedia is increased more rapidly. Many websites allows the user to upload and share multimedia objects such as audio, images, and videos. Without adding security information it is impossible to automatically verify the authenticity of the uploaded multimedia objects so the digital watermarking is used to protect the information against the illegal changes in the form of images, videos and audios. A digital watermark is the process of embedding watermark in a noise-tolerant signal such as an audio, video or image data used to identify ownership of the copyright of such signal. The robustness, fidelity, capacity are essential requirements of watermarking techniques so that they can handle several types of image artefacts. This paper gives survey of different watermarking techniques for protecting digital contents.

Keywords: DCT, Watermark, hash value, QIM, Tamper Detection, DWT, RSA, PSNR.