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The substitution box (S-box) is the core component of any block cipher that creates confusion in the ciphertext. This research contributes to creating a substitution box based on bent Boolean functions. Bent Boolean functions are constructed using the Maiorana–McFarland method and used as the coordinate functions of the substitution box. They are maximal nonlinear and inherently imbalanced, making them unsuitable for direct use in constructing a confusion component. The imbalance nature of the coordinate Boolean function directly impacts the bijective property of the nonlinear component. To create a bijective confusion component, we focus on mitigating the imbalance of each coordinate Boolean function. The methodology adopted is simple and efficient as compared to other heuristic techniques. By defining an empty matrix and putting bent Boolean functions side by side as matrix elements, we shape the initial 2 n × k sized substitution box, k ∈ (2 ,... , n) . We limit the number of occurrences of each possible outcome of initial 2 n × k substitution box to make a bijective n × n S-box. These small initial S-boxes lay a good foundation for constructing strong subsequent S-boxes. Experimental results based on the generation of 8 × 8 substitution box indicate that the suggested algorithm outperforms other competing heuristic approaches in nonlinearity, while maintaining sufficient performance in the strict avalanche criterion, bit-independence, linear and differential probability properties. The suggested nonlinear component is tested using well-known images from the literature, and the histogram analysis of the confused images demonstrates a high degree of randomness. [ABSTRACT FROM AUTHOR]

The substitution box (S-box) is the only nonlinear component of any block cipher. It hides the relationship between the key and the cipher text. Several methods are available in the literature for creating S-boxes of different sizes. However, the need to design 4 × 4 S-boxes for lightweight encryption is in demand. The suggested method first generates the initial S-boxes from the elliptic curve points, and then the S-boxes are evolved with the help of algebraic group structures. Algebraic group structures have the potential to improve their cryptographic strength. The cryptographic properties of the suggested S-boxes, such as nonlinearity, algebraic degree, branch number, and bijectivity, are analyzed. We also present a comparative analysis of the suggested S-boxes with different standard S-boxes. The offered S-boxes are utilized in an image steganography scheme. First, the secret image is encrypted through the combination of the substitution operation and the bitwise XOR of the key. The enciphered image is hidden in the cover image using the least significant bit of steganographic scheme. Experimental results show that the suggested algorithm has a high security level and better stego-image quality. [ABSTRACT FROM AUTHOR]

The strength of any block cipher depends on the key size, total number of rounds and the strength of confusion component against differential cryptanalysis. Data encryption standard (DES) as a block cipher has enjoyed a worldwide acceptance for more than three decades. It is a symmetric block cipher and considered to be very strong against all known attacks at that time. It uses 64-bit key size and block size, but the advancement in technology results in increasing the speed of the computers and thus makes DES not secure any more. The shorter key size is the weak area of DES. In this article, we have increased the block size as well as the key size from 64 to 128 bits. The internal structure of our proposed mechanism ultimately changed all other components of DES accordingly. By this improvement, our anticipated scheme is more secure due to its robust due to its confusion and diffusion components. The algorithm is applied on the plain text and on images. We have performed the standard benchmarks statistical analyses on our suggested encryption scheme in order to authenticate the anticipated mechanism. [ABSTRACT FROM AUTHOR]