Ghulam Murtaza

We propose a new parametrization of the resonant Rossby/drift wave triads to develop an algorithm to enumerate all resonant triads in a given grid of wavenumbers. To arrive at such a parametrization, we have employed tools from arithmetic/algebraic geometry to project resonant triads on a certain class of conics. Further, we extend the newly developed algorithm for the enumeration of quasi-resonant triads and experimentally show that the said algorithm is robust to design the network of quasi-resonances. From the experimental results, we observed that the new algorithm enumerates all triads in low computation time when compared with the existing methods. Finally, we apply this work to information security by constructing a total order on the enumerated resonant triads to design a substitution box (S-box) generator. Via extensive analyses over several indicators (nonlinearity, algebraic complexity, linear and differential approximation probabilities, strict avalanche criteria, and bit independence criterion) we show that the newly developed S-box outperforms the S-boxes constructed by most of the existing schemes.

Developing a substitution-box (S-box) generator that can efficiently generate a highly dynamic S-box with good cryptographic properties is a hot topic in the field of cryptography. Recently, elliptic curve (EC)-based S-box generators have shown promising results. However, these generators use large ECs to generate highly dynamic S-boxes and thus may not be suitable for lightweight cryptography, where the computational power is limited. The aim of this paper is to develop and implement such an S-box generator that can be used in lightweight cryptography and perform better in terms of computation time and security resistance than recently designed S-box generators. To achieve this goal, we use ordered ECs of small size and binary sequences to generate certain sequences of integers which are then used to generate S-boxes. We performed several standard analyses to test the efficiency of the proposed generator. On an average, the proposed generator can generate an S-box in 0.003 seconds, and from 20,000 S-boxes generated by the proposed generator, S-boxes have at least the nonlinearity 96. The linear approximation probability of 1000 S-boxes that have the best nonlinearity is in the range [0.117, 0.172] and more than 99% S-boxes have algebraic complexity at least 251. All these S-boxes have the differential approximation probability value in the interval [0.039, 0.063]. Computational results and comparisons suggest that our newly developed generator takes less running time and has high security against modern attacks as compared to several existing well-known generators, and hence, our generator is suitable for lightweight cryptography. Furthermore, the usage of binary sequences in our generator allows generating plaintext-dependent S-boxes which is crucial to resist chosen-plaintext attacks.