  In this contribution we propose a novel steganographic method based on
several orthogonal polynomials and their combinations. The steganographic
algorithm embeds a secrete message at the first eight coefficients of high
frequency image. Moreover, this embedding method uses the Beta chaotic map to
determine the order of the blocks where the secret bits will be inserted. In
addition, from a 128-bit private key and the steps of a cryptography algorithm
according to the Advanced Encryption Standard (AES) to generate the key
expansion, the proposed method generates a key expansion of 2560 bits, with the
purpose to permute the first eight coefficients of high frequency before the
insertion. The insertion takes eventually place at the first eight high
frequency coefficients in the transformed orthogonal moments domain. Before the
insertion of the message the image undergoes a series of transformations. After
the insertion the inverse transformations are applied to the original
transformations in reverse order. The experimental work on the validation of
the algorithm consists of the calculation of the Peak Signal-to-Noise Ratio
(PSNR), the Universal Image Quality Index (UIQI), the Image Fidelity (IF), and
the Relative Entropy (RE), comparing the same characteristics for the cover and
stego image. The proposed algorithm improves the level of imperceptibility and
security analyzed through the PSNR and RE values, respectively.
