13-11-2012, 11:44 AM
CONFUSION-DIFFUSION MECHANISM FOR CHAOS-BASED IMAGE CRYPTOSTSTEMS
CONFUSION-DIFFUSION.doc (Size: 128 KB / Downloads: 26)
ABSTRACT
With the fast development of the computer technology and information processing technology, the problem of information security is becoming more and more important. Information hiding is usually used to protect the important information from disclosing when it is transmitting over an insecure channel. Images are routinely used in diverse areas such as medical, military, science, engineering, art, entertainment, advertising, education as well as training. With the increasing use of digital techniques for transmitting and storing images, the fundamental issue of protecting the confidentiality, integrity as well as the authenticity of images has become a major concern.
A multi-dimensional chaotic map is usually employed in the confusion stage for image pixel permutation while a one-dimensional (1D) chaotic map is used for diffusion purpose. The proposed algorithm is based on two dimensional (2D) diffusion process which gives higher levels of security to the image. The security analysis of the proposed algorithm is given.
This mixture application of chaotic maps shows advantages of large key space and high-level security. The cipher text generated by this cryptosystem is the same size as the plaintext size and is suitable for practical use in the secure transmission of confidential information over the Internet.
INTRODUCTION
Secure transmission of confidential digital images has become a common interest in both research and applications. Image encryption is different from text encryption due to some intrinsic properties of images such as bulky data capacity and high redundancy, which are generally difficult to handle by using traditional techniques. The main obstacle in designing effective image encryption algorithms is that it is rather difficult to swiftly shuffle and diffuse such image data by traditional cryptographic means. With the desirable properties of pseudo-randomness, ergodicity, high sensitivity to initial conditions and parameters, chaotic maps have demonstrated great potential for information especially image encryption. The nature of chaos has initiated a lot of interests in different engineering disciplines, where cryptography must be one of the most potential applications. The distinct properties of chaos, such as ergodicity, quasi-randomness, sensitivity dependence on initial conditions and system parameters, have granted chaotic dynamics as a promising alternative for the conventional cryptographic algorithms. As the basis for developing cryptosystem, the advantage of chaos lies in its random behavior and sensitivity to initial conditions and parameter settings to fulfill the classic Shannon requirements of confusion and diffusion.
Problem Definition
Image encryption is different from text encryption due to some intrinsic properties of images such as bulky data capacity and high redundancy, which are generally difficult to handle by using traditional techniques. The main obstacle in designing effective image encryption algorithms is that it is rather difficult to swiftly shuffle and diffuse such image data by traditional cryptographic means.
Proposed solution:
A chaos-based image encryption algorithm with combined confusion and diffusion mechanisms is proposed. It gives the the relation between the involved chaotic map and the security of the cryptosystem. The encryption scheme is composed of two steps: chaotic confusion and pixel diffusion, where the former process permutes a plain-image with a 2D chaotic map, and the latter process changes the value of each pixel one by one. In the confusion process, the parameters of the chaotic map serve as the confusion key; in the diffusion process, such parameters as the initial value or control parameter of the diffusion function serve as the diffusion key.
Advantages
It is robust against all kinds of cryptanalytic, statistical attack, differential attack, and various brute-force attacks hence more secure.
It provides security against statistical attack, known-plaintext attack, select- plaintext attack.