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The PASCAL Visual Object Classes Challenge

The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

[서평]「Applied Cryptography」

The number of changing pixel rate (NPCR) and the unified averaged changed intensity (UACI) are two most common quantities used to evaluate the strength of image encryption algorithms/ciphers with respect to differential attacks. Conventionally, a high NPCR/UACI score is usually interpreted as a high resistance to differential attacks. However, it is not clear how high NPCR/UACI is such that the image cipher indeed has a high security level. In this paper, we approach this problem by establishing a mathematical model for ideally encrypted images and then derive expectations and variances of NPCR and UACI under this model. Further, these theoretical values are used to form statistical hypothesis NPCR and UACI tests. Critical values of tests are consequently derived and calculated both symbolically and numerically. As a result, the question of whether a given NPCR/UACI score is sufficiently high such that it is not discernible from ideally encrypted images is answered by comparing actual NPCR/UACI scores with corresponding critical values. Experimental results using the NPCR and UACI randomness tests show that many existing image encryption methods are actually not as good as they are purported, although some methods do pass these randomness tests.

NPCR and UACI Randomness Tests for Image Encryption

A new 1D chaotic system for image encryption

An image encryption scheme using reverse 2-dimensional chaotic map and dependent diffusion

Compound hyper-chaotic system is a chaotic system that combines two or more hyper-chaotic systems. In this paper, we propose a 2-dimensional compound homogeneous hyper-chaotic system (CHHCS) and local binary pattern (LBP)-based image encryption algorithm, which includes the CHHCS-based permutation operation and the LBP-based diffusion operation. Firstly, we employ a new CHHCS and prove the good hyper-chaotic behaviors, and we use CHHCS to permutate the plain image twice to obtain good permutation effect. Then, every permutated pixel is diffused with dynamic LBP operation, which means even the same permutated pixel will be encrypted to different cipher value. Finally, we provide some theoretical analyses and simulations to confirm the security and the validity of the proposed algorithm.

An image encryption algorithm based on compound homogeneous hyper-chaotic system

In traditional permutation-diffusion type image cipher, the confusion and diffusion are two independent procedures. In general, several overall rounds are required to achieve a satisfactory security level, which downgrades its advantage in online image protection. In this paper, a novel plain pixel-related swapping confusion approach that can contribute considerable diffusion effect in the permutation procedure is proposed. By employing the self-related non-linear pixel swapping confusion approach, a tiny difference between two plain images can bring about completely different confused images. Therefore, the spreading process of the cryptosystem is significantly accelerated, and the workload of the time-consuming diffusion part will be reduced. Moreover, an improved image encryption architecture is proposed in conjunction with the pixel swapping-based confusion approach. Compared with the typical permutation-diffusion structure, the new architecture well addresses the weakness of confusion key sensitivity in the first encryption round. Simulation results and numerical analyses justify the higher efficiency and sufficient strength of the proposed image encryption scheme.

Hai Yu

Papers

An image encryption scheme using reverse 2-dimensional chaotic map and dependent diffusion

An image encryption algorithm based on compound homogeneous hyper-chaotic system

A fast image encryption scheme with a novel pixel swapping-based confusion approach

An efficient image encryption scheme using gray code based permutation approach

Analysis and improvement of a double-image encryption scheme using pixel scrambling technique in gyrator domains