Abstract: Watermarking is hiding digital information in a carrier signal. Digital Watermark verifies the Authenticity or Integrity of the Carrier Signals or shows Identity of its owners. Watermark works as Tag or Ownership Identifier. Basically watermark is a secondary image that is imposed on the original image for protecting that image. Today in the emerging world of internet digital watermarking is becoming very important. Digital watermarking is used in various applications like-copyright protection, tamper detection, broadcast monitoring, authentication, integrity, and verification. Image processing use voluminous methods for digital watermarking. This following paper is a survey of various watermarking techniques and presents a brief introduction to these methods used for watermarking.

Keywords: Digital watermarking, Spatial Domain Techniques, Frequency Domain Techniques, Least significant Bit, SSM Modulation, Discrete Cosine Transform, Discrete Wavelet Transformation, Discrete fourier Transform .