During the recent years several chaotic image encryption algorithms based on one dimensional (1-D) have been proposed, but the drawbacks of small key space, low speed, and low security in 1-D chaotic cryptosystems are obvious. This paper proposes a new image encryption technique based on 1-D and 2-D chaotic maps which provide more security and big key space. The 1-D chaotic system is induced from a mathematical combination between the logistic map and the cubic chaotic map. It has the advantage of bigger key space and high security analysis such as key space analysis, statistical analysis and sensitivity analysis were carried out. The proposed system uses 1-D and 2-D chaotic maps for simultaneous encryption of the components R, G, B of the colored image; these three components affect each other. So, the security and confidentiality of image data become more important. The security of digital images and performance speed has become more important since the communications of digital information over network occur more frequently. An image encryption has applications in various fields for example; the internet communication, the multimedia systems, the medical imaging, Tele-medicine and the military communication. The image encryption's aim is to convert the original image to another image that is hard to understand. However, image encryption differs from text encryption due to some intrinsic features of images which include bulk data capacities, high redundancy, strong correlations among pixels, etc. These features make conventional cipher systems such as DES, AES and RSA unsuitable for practical image encryption [1]. The chaos theory is used in cryptography due to its intrinsic features. These properties of chaos includes: sensitivity to initial condition and control parameters, random like behavior and mixing property, etc [2]. Several chaos based image encryption approaches have been described. The first is the confusion approach where the position of pixels scrambled without changing the values of pixels, the application of this approach does not guarantee a good level of security [3]. The second approach is the diffusion which aims to change the value of each pixel in the whole image [4]. Other approach shuffles the positions of plain-image in spatial domain by cat map [5-7]. To enhance the security, the majority of methods propose to mix between more than one approach simultaneously. Some conditions should be fulfilled such as a large key space, randomness of the cipher-image and a high sensitivity on the initial conditions. In [8], an image encryption scheme based on improved 3-D cat map is proposed. Shuffling the positions with Henon map and changing the grey values of image pixels with improved 2-D Logistic map are combined simultaneously to ensure the security of our scheme. New color image encryption algorithms encrypt the three components R, G, B of the color image. The common drawback of these algorithms is: they neglect the correlations between the components R, G, B and are more vulnerable to attack [9-15]. To overcome this problem, a novel color image encryption algorithm based on 1-D chaos map is described for the encryption R, G and B components of color image at the same time and made the three components affect each other [16]. In this paper, a new chaotic map which combines the logistic map and cubic map is used as a 1-D chaotic system to shuffle the position of blocks of the three components of image, on the other side the 2-D logistic map is used to rearrange the position of image pixels. These two chaotic systems are used to encrypt R, G, and B components of color image at the same time and made the three components affect each other. The current algorithm consists of 3 phases. Phase-1 creates a 1-D chaotic system, its initial values and scrambles the blocks of the image. Phase-2 uses a 2-D chaotic system to scrambling the rows and columns and increases the quadratic coupling of the items? y?_i^2, x_i^2, x_i y_i this provides more security to the system. Phase-3 uses the 1-D chaotic system again to change the values of pixels. The rest of this paper is organized as follows: section 2 describes the proposed chaotic system. Section 3 describes the proposed image encryption algorithm. section4 describes the image decryption algorithm. Section 5 experimental results and performance analysis are reported. Section 6 presents the conclusion.

Image Encryption Algorithms Pixels Diffusion Block Shuffling Image Decryption