This paper blends the ideas from recent researches into a simple, yet efficient image encryption scheme for colored images. It is based on the finite field cosine transform (FFCT) and symmetric-key cryptography. The FFCT is used to scramble the image yielding an image with a uniform histogram. The FFCT has been chosen as it works with integers modulo p and hence avoids numerical inaccuracies inherent to other transforms. Fractals are used as a source of randomness to generate a one-time-pad keystream to be employed in enciphering step. The fractal images are scanned in zigzag manner to ensure decorrelation of adjacent pixels values in order to guarantee a strong key. The performance of the proposed algorithm is evaluated using standard statistical analysis techniques. Moreover, sensitivity analysis techniques such as resistance to differential attacks measures, mean square error, and one bit change in system key have been investigated. Furthermore, security of the proposed scheme against classical cryptographic attacks has been analyzed. The obtained results show great potential of the proposed scheme and competitiveness with other schemes in literature. Additionally, the algorithm lends itself to parallel processing adding to its computational efficiency.

This paper presents a new approach for secure hiding of textual data in a colored digital image. Use of images as a cover media in steganography is based on the deficiencies in the human visual system (HVS). The proposed technique employs two independent chaotic sequences for specifying the locations where the message bits are embedded in the cover image using an adapted version of the least significant bit (LSB) method. Message bits are embedded using the 3-3-2 LSB insertion method for the chaotically selected pixels of the cover image. This technique provides sufficient security as the same sequence of numbers cannot be generated without knowing the exact key; that is; the initial conditions of the two chaotic maps used in the index selection process. Moreover, the preliminary results ensure that eavesdroppers will not have any suspicion that there is a message hidden within the sent image since the peak signal to noise ratio (PSNR) is high and the mean-squared-error (MSE) is low. Furthermore, the length of the secret message is another important component of the key, which standard steganography detection methods cannot estimate correctly. Finally, the proposed approach provides better PSNR values and MSE values compared to other existing techniques as apparent from our experimental results.

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