May 2017, Volume 4, Issue 05 JETIR (ISSN-2349-5162) JETIR1705044 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 221 ENCRYPTION AND DECRYPTION METHOD OF IMAGES USING STEGANOGRAPHY Akanksha Dwivedi 1 , Rohit Miri 2 1 M Tech scholar, Department of Computer science engineering, C V Raman University bilaspur, C.G., India 2 Associate Professor,Department of Computer Science Engineering, C V Raman University bilaspur, C.G., India ABSTRACT: Watermarking is the process of embedding new data into image, audio or video. Digital Watermarking technique is used to hide a secret or personal message to protect a products copyright or to demonstrate data integrity. To provide double protection, after the watermarking process, the watermarked image tends to go through an encryption process using CHAKRA – symmetry key encryption algorithm which encrypts the data with the concepts of Cartesian coordinate geometry and circle generation. In this paper, we perform watermarking on different types of images like BMP, JPEG etc.., and the input image is pre-processed and converted into JPEG-LS format which contains enhanced quality. Keywords: JPEG Steganography, uniform embedding, distortion function design. 1. INTRODUCTION Digital Watermarking technique is used to hide a small image in jpeg, jpg, bmp image of data in a digital signal in such a wa y that it can’t be detected by viewer. A digital watermark can be either visible or invisible. A visible watermark is a visible semi-transparent text or image overlaid on the original image. It allows the original image to be viewed, but it still provides copyright protection by marking the image as its owner’s property. Visible watermarks are more robust against image transformation especially if we use a semi-transparent watermark placed over whole image.Thus they are preferable for strong copyright protection of intellectual property that’s in digital format. An invisible watermark is an embedded image which cannot be perceived with human’s eyes. Only electronic devices or specialized software can extract the hidden information to identify the copyright owner. Invisible watermarks are used to mark a specialized digital content like text, images or even audio content to prove its authenticity[9]. Typical applications of digital watermarking can include broadcast monitoring, owner identification, proof of ownership, transaction tracking, content authentication, copy control, device control legacy enhancement and content description. II DIFFERENT DOMAINS IN WATERMARKING TECHNIQUES The digital image watermarking techniques in the literature are typically grouped in two classes: Spatial domain techniques [5]: which embed the watermark by modifying the pixel values of the original image and the transform domain techniques which embed the watermark in the domain of an invertible transform. The discrete cosines transform (DCT) and the discrete wavelet transform (DWT) are commonly used for watermarking purposes[6]. The transform domain algorithms modify a subset of the transform coefficients with the watermarking data and generally achieve better robustness than spatial domain methods. A. Discrete Cosine Transform (DCT) The discrete cosine transform (DCT) is a technique for converting a signal into elementary frequency components. It converts a spatial domain waveform into its constituent frequency components as represented by a set of coefficients. The process of reconstructing a set of spatial domain samples is called the Inverse Discrete Cosine Transform (IDCT). It is widely used in image compression. B. Discrete Wavelet Transform (DWT) Wavelet Transform is a signal processing technique that decomposes a signal or image into different frequency sub bands at number of levels and multiple resolutions. Initially, the input image is decomposed into four levels by a DWT, resulting in an approximation sub band with low frequency components and 12 detail sub bands with high frequency components. The DWT (Discrete Wavelet Transform) separates an image into a lower resolution approximation image (LL) as components well as horizontal (HL), vertical (LH) and diagonal (HH) detail components. C. Singular Value Decomposition (SVD) Another transform domain which is being exploited is Singular Value Decomposition (SVD) due to its simplicity in implementation and attractive mathematical features. It is one of the most powerful numerical analysis technique and used in various applications. Some SVD based algorithms are purely SVD based in a sense that only SVD domain is used to embed watermark into image. III DIFFERENT APPROACHES FOR WATERMARK EMBEDDING TECHNIQUES A. Semi-Fragile Watermarking Approach for Color JPEG Image The authors [4] proposed a semi-fragile watermarking scheme for colour JPEG image in compressed domain. A chaotic map model based on authentication generating model is introduced. It is sensitive to malicious manipulations and Image authentication is provided to overcome tampering. But it doesn’t work for other image formats except JPEG. More number of parameters is used in this approach which occupies more space. B. Watermark Embedding and Extraction Approach For JPEG2000 Compressed and Encrypted Images The authors [3] proposed a robust watermarking algorithm used to watermark JPEG2000 compressed and encrypted images. The encryption algorithm used is a stream cipher RC4 approach. In this approach, it embeds watermark in the compressed-encrypted domain, the extraction of watermark can be done in the decrypted domain. The advantage of this approach is that it preserves the confidentiality of content as the