Secure Data Transmission Using Optimized Cryptography and Steganography Using Syndrome-Trellis Coding

The establishment of secure data transmission among two communicating parties has become challenging. It is due to unexpected attacks during communication over an unsecured transmission channel. The security of secret data is secured by cryptography and steganography. Hence, this work introduces a secure data transmission model by improving the strength of hybrid cryptography and steganography approaches. It is based on an optimized substitution box (S-box) and a texture-based distortion function. The secret data is initially encrypted using a substitution-permutation network-based chaotic system in this approach. This cryptographic algorithm contains two stages: confusion and diffusion stages. The substitution box attains confusion, and the permutation box attains diffusion. However, the security of this cryptosystem strongly depends on the quality of the S-boxes. Hence, a new arithmetic optimization algorithm (AOA) is proposed to create a robust S-box with a high non-linearity score. After encrypting the secret data, the cover elements have been extracted from the embedded domain created using the sign of DCT (Discrete cosine transform) coefficients. Here, the cover elements selection is optimized by re-compressing the cover JPEG image to exclude the zero-valued DCT coefficients. Then, the embedding cost is calculated by developing a new texture-based distortion function to embed more secret data into the texture portion because the visual quality of the texture portions is not affected due to the embedding process. Finally, the encrypted data has been embedded into cover elements using Syndrome-Trellis Coding (STC) to obtain the stego elements. The overall implementation is carried out in the MATLAB platform. The developed model is evaluated based on imperceptibility and undetectability.