International Journal of Computer Applications (0975 – 8887) Volume 108 – No. 9, December 2014 11 New Image Broadcasting based on Visual Cryptography and Steganography Dhiaa Alzubaydi Associate professor, Department of Computer Science, University of Al-Mustansiriyah Dina R. Alshibani Department of Computer Science, University of Al-Mustansiriyah ABSTRACT This paper presents a new security system by combining cryptographic and steganographic Technique. The main idea behind the present work is to divide the participants into different security levels, determining which participant will be able to decrypt the secret image, and which participant will not be able to decrypt the secret image. A modified idea of traditional visual cryptography with pixel expansion will be introduced to encrypt the data. The hiding method is based on hiding the pixel of the encrypted secret image in a colored cover by altering the DCT coefficients of the cover image. Before the hiding process Arnold transformation is performed on the cover image. The results show that the stego-image is closed related to the original cover image, with good impressibility. General Terms Security Keywords Visual Cryptography, steganography, DCT, Arnold Transform, bit plane. 1. INTRODUCTION A. Visual Cryptography: Visual cryptography is a special encryption, which provides information security, which uses uncomplicated algorithm unlike the complex, computationally exhaustive algorithms used in other techniques like conventional cryptography. This technique allows visual information (pictures, text, etc) to be encrypted in such a way that their decryption can be performed by the human visual system, without any complex cryptographic algorithms. This technique encrypts a secret image into shadows such that combining enough number of shadows reveals the secret image. Shadows are usually presented in transparencies [1]. B. Steganography: Steganography is the art and science of script secreted messages in such a way that no one, apart from the sender and planned recipient, suspects the existence of the message. Images are the most popular cover objects used for Steganography. The properties like robustness and embedding capacity should be carefully considered when scheming a steganography algorithm [2]. 2. RELATED WORK: In 2005 Jithesh and Dr. Kumar [3], suggest blending of both steganography and visual cryptography. The steganography technique used here is Discrete Cosine Transform Technique [DCT], the most reliable type of steganography technique and the new type of cryptography technique which is Visual Cryptograp hy. In 2008 Al-Anani et al. [4], presents a new technique to hide more than one colored encrypted image with encrypted data in a meaningful colored cover image. The hidden secret images with their encrypted data can be extracted using different masks of the same cover image. One could retrieve the hidden information, which is customized to his own purposes relative to the mask designed for a particular purpose only. The same mask is used to encrypt both the secret data and the secret image in which data is hidden. This technique increases the level of security as well as the payload. In 2012 Surekha and Dr. Swamy [5], in this paper, a spatial domain image watermarking technique based on Visual Secret Sharing (VSS) and unique statistical properties is proposed. A key looking image is generated during watermark hiding process and is secretly registered with an arbitrator for verification during conflicts. Another random looking image is generated during watermark revelation stage and is combined with the existing one, to recover the watermark. This whole process is done without altering the image to be protected and hence the quality of the cover image is high. When compared with similar existing techniques, the proposed technique has two main advantages: Provides greater convenience in carrying and storing the intermediate images called shares; Provides high security. 3. MATERIAL AND METHODS 3.1 Arnold Transform: Arnold transform is selected as pre-treatment way for open image as it is uncomplicated and periodic. Arnold transform is a type of transform in the traversing theory, called as Arnold‟s cat mapping. Arnold transformation is defined as [6]: +1 = + … .1 +1 = + 2 … .2 where x n ,y n are the position of pixel in the orgin image, and n=1,2,3...n-1 and x n+1 , y n+1 are the transformed position after arnold transform. 3.2 Discrete Cosine Transform (DCT): Discrete cosine transform (DCT) is an important transform widely used in digital image processing. Large DCT coefficients are concentrated in the low frequency region; hence, it is known to have excellent energy compactness properties. The 2D discrete cosine transform of an image or 2D signal is defined as [7]: (, )= ()() , cos 2 +1 2 cos 2 +1 2 … 3 −1 =0 −1 =0 ()= , =0 , ≠ 0 ... 4 for , = 0,1,2, … , − 1 and () and () are defined in (4). The inverse transform is defined as: