Watermarking is used to verify the identity and authenticity of the owner of a digital image. It is a process in which the information which verifies the owner is embedded into the digital image or signal. These signals could be either videos or pictures or audios. There are two types of watermarking: visible watermarking and invisible watermarking. The two watermarking algorithms are explained with procedure of image, audio and video watermarking. The first algorithm is based on the Discrete Cosine Transform (DCT) (in the frequency domain) and the second algorithm is based on the Least Significant Bit (LSB) replacement (in the spatial domain). The results are compared under different kinds of attacks.

Steganography is the art and science of writing hidden messages in such a way that no one other than the intended recipient knows the existence of the message, as shown in Figure 1. It needs to be done without any knowledge of secret key used for embedding and may be even the embedding algorithm (Lu, 2005).

Watermarking is used to verify the identity and authenticity of the owner of a digital image. It is a process in which the information which verifies the owner is embedded into the digital image or signal. These signals could be either videos or pictures or audios. The focus is upon content identification to enable a wide range of applications that includes document track and trace, broadcast monitoring, device control and linking the physical and digital worlds. The embedded message in digital watermarking is usually related to the cover media, and its size is much smaller. It is the process of computer-aided information hiding in a carrier signal; the hidden information should, but does not need to, contain a relation to the carrier signal.

Computer Sciences Journal, Discrete Cosine Transform (DCT), Least Significant Bit (LSB), Steganography, Watermarking, Frequency Domain Technique, Spatial-Domain Technologies – LSB, Frequency-Domain Technologies – DCT, Discrete Fourier Transform (DFT).