A secure key dependent dynamic substitution method for symmetric cryptosystems.

The biggest challenge for symmetric cryptosystems is to replace their static substitution with dynamic substitution, because static substitution S-boxes make the symmetric block ciphers more vulnerable to attacks. Previous well-known dynamic key-dependent S-boxes are lacking in dynamicity and do not provide optimal security for symmetric block ciphers. Therefore, this research aims to contribute an effective and secure method for designing key-dependent dynamic S-box with dynamic permutations to make the symmetric block ciphers optimally secure. The proposed S-box method has been experimentally evaluated through several measures such as bit independence criteria, non-linearity, hamming distance, balanced output, strict avalanche criteria including differential and linear approximation probabilities. Moreover, the randomness properties of proposed method have also been evaluated through several standard statistical tests as recommended by the National Institute of Standards and Technology (NIST). Thus, the results show that the proposed method, not only retains effective randomness properties but it also contains, good avalanche effect (up to 62.32%) which is significantly improved than others. Therefore, the proposed substitution method is highly sensitive to the secret key because, only a single bit change in key generates an entirely new S-box with all 256 values at different positions. Thus, the overall evaluation shows that the proposed substitution method is optimally secure and outperforming as compared to the existing S-box techniques. In future, the proposed method can be extended for different key sizes (192-256 bits) or even more.

Optimal sequence for chain matrix multiplication using evolutionary algorithm.

The Chain Matrix Multiplication Problem (CMMP) is an optimization problem that helps to find the optimal way of parenthesization for Chain Matrix Multiplication (CMM). This problem arises in various scientific applications such as in electronics, robotics, mathematical programing, and cryptography. For CMMP the researchers have proposed various techniques such as dynamic approach, arithmetic approach, and sequential multiplication. However, these techniques are deficient for providing optimal results for CMMP in terms of computational time and significant amount of scalar multiplication. In this article, we proposed a new model to minimize the Chain Matrix Multiplication (CMM) operations based on group counseling optimizer (GCO). Our experimental results and their analysis show that the proposed GCO model has achieved significant reduction of time with efficient speed when compared with sequential chain matrix multiplication approach. The proposed model provides good performance and reduces the multiplication operations varying from 45% to 96% when compared with sequential multiplication. Moreover, we evaluate our results with the best known dynamic programing and arithmetic multiplication approaches, which clearly demonstrate that proposed model outperforms in terms of computational time and space complexity.

Discovery of novel Hepatitis C virus inhibitor targeting multiple allosteric sites of NS5B polymerase.

HCV is a viral infection posing a severe global threat when left untreated progress to end-stage liver disease, including cirrhosis and HCC. The NS5B polymerase of HCV is the most potent target that harbors four allosteric binding sites that could interfere with the HCV infection. We present the discovery of a novel synthetic compound that harbors the potential of NS5B polymerase inhibition. All eight compounds belonging to the benzothiazine family of heterocycles displayed no cellular cytotoxicity in HepG2 cells at nontoxic dose concentration (200 µM). Subsequently, among eight compounds of the series, merely compound 5b exhibited significant inhibition of the expression of the HCV NS5B gene as compared to DMSO control in semi-quantitative PCR. Based on our western blot result, 5b at the range of 50, 100 and 200 µM induced 20, 40, and 70% inhibition of NS5B protein respectively. To estimate the binding potential, 5b was docked at respective allosteric sites followed by molecular dynamics (MD) simulations for a period of 20 ns. In addition, binding free energy calculation by MM-GB/PBSA method revealed a conserved interaction profile of residues lining the allosteric sites in agreement with the reported NS5B co-crystallized inhibitors. The presented results provide important information about a novel compound 5b which may facilitate the the discovery of novel inhibitors that tends to target multiple sites on NS5B polymerase.