International Journal of Computer Applications (0975 – 8887) International Conference on Distributed Computing and Internet Technology (ICDCIT-2015) 1 Image Steganography using Index based Chaotic Mapping Shreenandan Kumar, Suman Kumari, Sucheta Patro, Tushar Shandilya, Anuja Kumar Acharya School of Computer Engineering KIIT University, Bhubaneswar, India ABSTRACT There have been many techniques for hiding messages in images in such a manner that the alterations made to the image are perceptually indiscernible. The Least-significant bit (LSB)-based approach is the most popular type of steganographic algorithm. However, we find that in most existing approaches the choice of embedding positions within the cover image are not secure enough. In this paper, we have used 1D chaotic logistic map to generate the pseudo random numbers; the index values of the sorted pseudo random numbers are the positions used to embed the message in the cover image. This technique provides sufficient security as the same set of numbers cannot be generated without knowing the exact key and thus the message is more secure. The proposed technique has been applied and tested successfully on various images producing significant results. Keywords Steganography; chaotic map; logistic map; LSB technique. 1. INTRODUCTION Recently, due to growing internet technologies, there has been a lot of research in the field of data hiding and data security while transmitting the confidential data. The main features of a steganographic system are to get high load capacity and decrease the amount of noise in network/channel. Due to the conflicting behavior of these features, it is not easy to get them at the same time. So, most of the techniques mainly work on improving the space efficiency and stego quality. The conventional method used for steganography is the LSB technique where each message bit is embedded in the least significant bit of each pixel of the cover image [1], [2].These methods possesses high hiding capacity and imperceptibility but these are not secure to the attacks made to extract the message as the embedding positions are known. The methods proposed by Ali Daneshkhah [3] and Wang [4] along with some other techniques proposed [5], [6] has shown variation in the embedding positions to overcome this attack. Here in this paper a new technique has been applied to increase the hiding capacity and security of the embedding positions. This algorithm has been put forward for LSB based image steganography in which the last bits of the cover image are replaced by the bits of the message image which is encrypted using Index based 1D logistic chaotic map [7]. Pseudo random numbers are generated using the 1D logistic map which are sorted and their index value is used as the key. The decryption of message image is impossible without the correct key. This increases the security of the whole steganography system. This proposed model has been applied for image messages and texts messages showing better imperceptibility. The rest of the paper is organized as follows. In Section 2, the proposed steganography system is described. The simulation results are shown in Section 3 and Section 4 includes summary and conclusion for the proposed model. 2. PROPOSED MODEL 2.1 Generation of Pseudo Random Numbers Keeping security of the data as the main focus, chaotic map has been used in the proposed model. These are highly sensitive to the initial conditions. This paper has focused on 1D logistic mapping which is shown in equation (1).   +1 =   (1 −  ) (1) Here   is the initial value and will be between (0, 1). The equation is very sensitive to small change in the value of r (seed value) and the initial parameter   . The behavior of signal is completely chaotic (Figure 1.c) for the value of r in the range [3.56, 4] as compared to values outside the range and also there will be fewer tendencies for cyclic randomness. (a) (b)