Henan Normal University

About: Henan Normal University is a education organization based out in Xinxiang, China. It is known for research contribution in the topics: Catalysis & Ionic liquid. The organization has 10863 authors who have published 11077 publications receiving 166773 citations.

Cryptanalysis and improvement in a chaotic image cipher using two-round permutation and diffusion

Abstract: Cryptanalysis is significant for the design of secure image cryptosystem. Recently, a chaotic image encryption scheme using two rounds of Latin square-based permutation and diffusion was proposed. Although two-round encryption is used, the cryptosystem has still been cracked successfully by the combined attack using both chosen-plaintext attack (CPA) and chosen-ciphertext attack due to the inherent flaw that the same key was used in both permutation and diffusion phases of each round. Therefore, different keys are used in each encryption phase of the improved cryptosystem. However, in this paper, we further attacked the two-round encryption with different keys using only CPA. By counting the number of the diffused pixels in the first diffusion phase from the processed encrypted image, the first permutation of one pixel is confirmed, and then the whole equivalent key stream of the first permutation can be obtained by limited CPA. Based on this, the key stream of the third permutation phase is obtained in a similar way. Meanwhile, all the mappings of the fourth diffusion are collected by 256 CPA, and 17 possible mappings in average are selected by verification. Finally, the key stream of the second diffusion is obtained using two pairs of chosen images. Experiments show that the encrypted image can be cracked successfully by the proposed attack. This work is instructive to the cryptanalysis of multi-round encryption. In order to remedy the security weakness, an improved cryptosystem is also proposed, followed by thorough security analysis.

CO catalytic oxidation on Al-doped graphene-like ZnO monolayer sheets: a first-principles study

Abstract: The graphene-like ZnO (g-ZnO) monolayer sheet is a new class of two-dimensional materials with unique properties, which are still largely unexplored. This work studied the modulation of electronic structures and chemical activities of the g-ZnO monolayer sheet by substituting Al for host Zn atoms. It is found that replacing Zn with Al atoms is both energetically and dynamically highly favorable. Al doping introduces electrons into the conduction band of the g-ZnO monolayer sheet, which should significantly enhance the conductance and the chemical activity of the sheet. The CO oxidation by the lattice O atoms via the Mars–van Krevelen mechanism, and by the adsorbed O2via the Langmuir–Hinshelwood and Eley–Rideal mechanisms were comparably studied. The Al-doped g-ZnO monolayer sheet shows good catalytic activity for the CO oxidation via the more favorable Eley–Rideal mechanism with a two-step route. The study presents an effective strategy to tune the electronic structure and the chemical activity of the g-ZnO nanosheets, and gives us an insight into the mechanism of Al-doped ZnO nanostructures sensing reducing gases.

Cooperative photoredox and chiral hydrogen-bonding catalysis

Abstract: Chiral hydrogen-bonding catalysis is a classic strategy in asymmetric organocatalysis, and it has been extensively used in a variety of fundamental chemical transformations. At the same time, visible light-driven photoredox catalysis is a powerful and sustainable tool commonly used in radical chemistry. The intriguing combination of these two catalysis platforms would open a new avenue for the direct and highly efficient synthesis of enantioenriched compounds. Inspired by the conceptual breakthrough of T. Bach, in recent years, significant progress has been made in cooperative photoredox and chiral hydrogen-bonding catalysis. By developing a variety of important types of reactions, a wide range of valuable chiral compounds have been successfully synthesized. In this review, the advances in this key area are systematically described, and the examples are organized according to the distinct bond-forming patterns in the construction of the stereocentres.