Multi-Layers of Data Security System: Encrypted Image in Image Steganography

Abstract

Steganography is the art and science of conducting communication between two or more entities in a cover fashion. Image-in-Image steganography is adopted in the proposed stego-system of this work, where the security of secret image depends on a combination of two controls: Cryptography & Steganography, in the expectation that one security layer will compensate for a failure of another. Initially, the cryptography is used to increase the security immunity of the system and virtually nullify the value of an interception and the possibility of effective modification or fabrication, where the secret image is encrypted using dual encryption methods adopted by this work in order to provide another security layer of defense to the data that need to be protected. Consequently, the steganography is used to embed (hide) the encrypted secret image either into the frequency domain using Discrete Cosine Transform (DCT) or into the spatial domain using the Least-Nibble-Significant-Bits (LNSB ≡ 4-bits) or into a Variable-Single-Bit or into a Static-Single-Bit (1≤ n ≤ 8) of a cover image, without causing significant effect on the quality of the cover image especially when (n ≤ 6) according to “Compensation” & “Gap” concepts adopted in this work, in order to increase the robustness of the stego-system against attacks. The suggested system was tested on 530 different image samples of type JPEG, BMP (true color 24 bit/pixel, 256-colors, 8 bit/pixel gray-scale) with different dimensions. The obtained results prove that these methods are very effective according to the low Mean Square Error (MSE) and high Peak Signal to Noise Ratio (PSNR) and provide high embedding capacity (> 50%) and better PSNR close to (40 db) using DCT.