Hadi Mahmodi

CHAOTIC CRYPTOGRAPHIC SCHEME BASED ON COMPOSITION MAPS

In recent years, a growing number of cryptosystems based on chaos have been proposed. But most of them have encountered many problems such as small key space and weak security. In the present paper, a new kind of chaotic cryptosystem based on Composition of Trigonometric Chaotic Maps is proposed. These maps which are defined as ratios of polynomials of degree N, have interesting properties such as invariant measure, ergodicity, variable chaotic region with respect to the control parameters and ability to construct composition form of maps. We have used a composition of chaotic map to shuffle the position of image pixels. Another composition of chaotic map is used in diffusion process. According to the performed analysis, the introduced algorithm can satisfy the required performances such as high level security, large key space and the acceptable encryption speed.

A Novel Block Cipher Based on Hierarchy of One-Dimensional Composition Chaotic Maps

In the past few years, a number of image encryption algorithms based on chaotic maps have been proposed. One dimensional chaotic system with the advantages of high-level efficiency and simplicity, has been widely used. But many of them essentially encounter with problems such as small key space and weak security. To overcome these drawbacks, we introduce a new method of image encryption based on composition of trigonometric maps (CTMs). The proposed scheme utilises chaotic properties for image encryption via the chaotic composition maps. Experimental results show that the new cipher has satisfactory security with a large key space, which makes it a potential candidate for encryption. It is practicable and reliable, with high potential to be adopted for Internet image encryption, transmission applications and other information security fields.

A new image encryption algorithm based on one-dimensional polynomial chaotic maps

In recent years, a growing number of cryptosystems based on chaos have been proposed, however, most of them encounter with some problems such as: low level of security and small key space. Chaotic maps have good properties such as ergodicity, sensitivity to initial conditions and control parameters, etc. Due to these features, they are good candidate for information encryption. In this paper, encryption based on the Polynomial Chaotic Maps (PCMs) is proposed. The theoretic and simulation results state that the proposed algorithm has many properties such as high speed and large key space and high security. Therefore it is suitable for practical use in the secure communications.

Performance enhancement of deep violet indium gallium nitride double quantum well lasers using delta barrier close to electron blocking layer

A thin aluminum gallium nitride (AlGaN) electron blocking layer (EBL), above the active region, is used to improve the performance and reduce threshold current of indium gallium nitride (InGaN) quantum well (QW) lasers. A new structure, with delta barrier close to EBL (AlGaN/0.3  nm GaN/InGaN), was devised to prevent deleterious polarization effects and confer other advantages. The effect of a 0.3 nm-thick GaN delta barrier on the performance of a deep violet InGaN double QW laser was investigated using ISE TCAD software. The results indicate that the delta barrier significantly enhances the output power, slope efficiency and external differential quantum efficiency while decreasing the threshold current.