Joint watermarking and fingerprinting approach for colored digital images in double DCT domain

Digital watermarking has developed immensely for multimedia uses in the current decade. The requirement for protected digital content grows vital with the enhancement in exchange of digital images on internet. Watermarking is a technique to safeguard digital media by retaining the owner´s possession. Fingerprinting extends the watermarking concept by embedding unique purchaser´s information. This paper presents a joint digital watermarking and fingerprinting approach for colored digital images applied in double DCT domain. The approach aims at copyright protection and traitor identification of digital images. Altered mid-frequency coefficients are analyzed by applying forward DCT transform. Watermark and fingerprint are embedded in a non-overlying manner. Second DCT allows for the precise determination of the block, for embedding data. The double domain can enhance the embedding capacity of the host image by choosing more than one coefficients in a given block. Simulation outcomes reveal that the watermark is immune to JPEG compression, additive noise and median filtering. Quality of the image is retained, as the results reveal a Peak Signal to Noise Ratio (PSNR) in range of 58-73 dB.