International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 03 Issue: 02 | Feb-2016 www.irjet.net p-ISSN: 2395-0072 © 2016, IRJET ISO 9001:2008 Certified Journal Page 1034 Technicalities of Digital Watermarking: A Review Er. Sandeep Kaur 1 , Er. Jaspreet Kaur 2 , Er. Inderpreet Kaur 2 1 M.Tech. Student, CSE, Rayat Bahra Group of institutes, Punjab, India 2 Assistant Professor, CSE, Rayat Bahra Group of institutes, Punjab, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract: For providing security to the digital media on internet the very useful technology is digital watermarking. Watermark is an image or pattern in document which is used to identify data authentication, data integrity. The user can check the watermarked information with the watermark key and watermarking extraction process. The various techniques of watermarking reviewed in this paper are Least Significant Bit (LSB), Robust, Discrete Cosine Transform (DCT), Spatial Domain, Frequency Domain, Blind and non-blind, Spread Spectrum. Out of these techniques, DCT, Spatial and Frequency based techniques are more efficient. These provide more refined images with less effort and are more secure and robust as compared with other techniques. Key words: Watermarking, DCT, Spatial, Frequency, Authentication, Security. 1. INTRODUCTION Digital images are composed of pixels. Each pixel represents the color of image at a single point. A pixel is a dot of any particular color in the image. Digital image processing is increasing with the technology increase. Digital image processing has many beneficial properties as compare to analogue image processing. Digital information is available on internet like images, audio, video, text and it is very easy to copy that data. To avoid this security issue Digital watermarking technique is used. Digital watermarking was introduced in 1993 [5][6]. Various purposes of watermarking are identity check, copy control, data abstraction, certification and authentication. Digital watermarking is an application of the digital image processing [2]. It is an information hiding technique. Watermark is an encrypted code like digital signature or certificate that attached to the original document. A watermark should be secret so that only the authorized person can legally access and modify the watermark. Watermarking technique is useful for fortification of images, video and text. When any unauthorized user tries to alter digital data, he/she can catch on the basis of retrieved watermark image. When digital data is share over the internet exchange of multimedia content copyright infringement issues are comes into the image. Digital watermarking techniques are of two types that are private and public watermark [3][13]. 1.1 Private watermark A private watermark might contain data for identifying the licensee to prove authentication. To retrieve information from secret watermark at least one secret key is required, which is generated by the sender. Embedded information includes serial numbers or licensee identifying hash values. A serial no is like a link to externally stored information. 1.2 Public watermark Public watermark is detected by the authorized receiver of copyrighted information. It contains information about copyright or licensee, such as copyright holder, the sender of the information or a URL link to fetch related information [16][17]. 2. WATERMARK FRAMEWORK Watermarking is a technique that embeds a watermark (secret code) or label into digital information. This process is known as watermark embedding process. In this process, the input to the scheme is the watermark, the cover media and a key. Key is used for security purpose, which prevents watermark from unauthorized access, recovery and manipulation. Every watermarking algorithm consists of three parts: I. The watermark II. The encoder III. The decoder The output of the watermarking scheme is the watermarked data [16][17]. In watermark detection process watermarked data, key and original watermark are the inputs. The output of the watermarking technique ensures that the information is authentic or not.