An Approach to Encrypt and Decrypt Satellite Images Based on S-box Matrix and RC4

Vollständiger Abstract

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In this work we propose a new advanced scheme of the encryption and decryption of the satellite images using a dynamically generated substitution box (S -box) matrix integrated with the RC4 stream cipher. The satellite images whose data is usually huge and contains strong spatial correlations among adjacent pixels are challenging to conventional encryption techniques that do not, in many cases, provide a high level of security. To reduce such problems, the developed method will use a dynamic S-box based on a secret key, which will increase the nonlinearity and the strength of the system in confusion. To achieve adequate diffusion of the image data, the RC4 algorithm is used to produce a pseudo-random keystream. In the encryption process, pixel values are initially operated on by an XOR operation with the keystream, and then operated on by a nonlinear substitution via the dynamic S -box. These steps are reversed in the decryption process, which uses the inverse S -box, and reusing the key stream, which would guarantee the exact reproduction of the original image, without the loss of information. The security performance of the framework was tested using comprehensive experimental tests in Python in the Google Collaboratory environment. We looked at such metrics as uniformity of histograms, entropy of information, adjacent-pixel correlation coefficients (horizontal, vertical, and diagonal), and indicators of differential attacks (NPCR and UACI). The findings reveal that the encrypted images have a very uniform distribution of histograms, the entropy measures are also near to the theoretical maximum of 8 and the correlation coefficients are virtually near to zero. Moreover, the scheme is highly resistant to the differential cryptanalysis with NPCR values of over 99% and UACI values of nearly 33%. Therefore, the developed method is effective in terms of the ability to unite high security and sensible calculation, making it an secure storage and transmission of satellite imagery during remote sensing processes.