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Abstract
Due to the open communication channels have greater vulnerability to security threats causing unauthorized information to be accessed. Securing the data during its transition in public domain channels (internet) becomes more important nowadays. Encryption and steganography are the common methods to secure communications. However, each one of them has a problem. So the work in this thesis focuses on overcoming their problem by amalgamating them to enhance the security. In this thesis, a new image steganography system has been proposed. The main features of the proposed system are; it has two layers of security, more embedding capacity relative to other existed methods, and very high stego image quality or Peak Signal-to-Noise Ratio (PSNR). On the other hand, the proposed system contains two proposed methods: The first proposed method enhances Pixel Value Difference (PVD) method by using Mobile Phone Keypad (MPK) encoding to increase the quality of stego-image (PSNR), called (PVD-MPK). The enhanced method is combined with the Modified Substitute Last Digit in Pixel by using Mobile Phone Keypad (MSLDIP-MPK) method to increase the capacity, this combination has been called PVD-MSLDIP- MPK. By using this combination, high Maximum Hiding Capacity (MHC) is achieved compared to other existed methods, in addition, the stego image likes the cover image, which means that this proposed method satisfies steganography objectives. The second proposed method focuses on overcoming the problems of encryption and steganography by combining encryption and steganography techniques to improve the security. This has been accomplished after modifying the Advanced Encryption Standard (AES) algorithm to be suitable for hiding data by using PVD- MSLDIP-MPK. The proposed method called AES-MPK