A LL Subband Based Digital Watermarking in DWT

Digital watermarking is a technique which allows an individual to add hidden copyright notices or other verification messages to digital audio, video, image and documents in such a way that the watermark cannot be removed against different attacks. Digital Watermarking is a process to prevent the unauthorized access and modification of data. It ensures that the communication between two parties' remains secure. Digital watermarking can be performed in spatial and frequency domain. In the spatial domain, the watermark is embedded in the very existence of the pixel. In frequency domain, the transformation of any kind is applied and then information is embedded. In this paper, we proposed an approach to watermarking in frequency domain using DWT technique. The gray scale host image is divided into four sub bands: LL, HL, LH, HH and the watermark are inserted in the LL sub band using DWT technique. As the image is divided into four sub bands, a watermark of equal size of the LL sub band is inserted and the results are analyzed on the bases of different parameters such as PSNR and MSE. LL represents the average component of the host image which contains the maximum information of the image. In this approach the watermark is inserted in LL sub band using XOR operation. As the table IV shows, the imperceptibility of this method is quite good. Also, it shows good results when compared with existing methods.