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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

Based on isosceles triangle segmentation, a new approach of color image compression has been proposed by using correlation among RGB components and fractal image compression algorithm in this paper. The encoding process in this paper is composed of two steps: transforming color image into gray-level image according to correlation among RGB and compressing fractal image based on isosceles triangle segmentation. Compared to the fractal color image compression method based on Jacquin, the approach proposed in this paper has better performance because the use of isosceles triangle segmentation greatly reduced the searching time. Simulation results show that the proposed method can effectively reduce the encoding time and improve compression ratio while remaining the quality of the retrieved image.

Fractal Color Image Coding Based on Isosceles Triangle Segmentation

Superpixels are widely used in computer vision applications. Most of the existing superpixel methods use established criteria to indiscriminately process all pixels, resulting in superpixel boundary adherence and regularity being unnecessarily inter-inhibitive. This study builds upon a previous work by proposing a new segmentation strategy that classifies image content into meaningful areas containing object boundaries and meaningless parts that include color-homogeneous and texture-rich regions. Based on this classification, we design two distinct criteria to process the pixels in different environments to achieve highly accurate superpixels in content-meaningful areas and keep the regularity of the superpixels in content-meaningless regions. Additionally, we add a group of weights when adopting the color feature, successfully reducing the undersegmentation error. The superior accuracy and the moderate compactness achieved by the proposed method in comparative experiments with several state-of-the-art methods indicate that the content-adaptive criteria efficiently reduce the compromise between boundary adherence and compactness.

Superpixels With Content-Adaptive Criteria

In this paper, an finite-time synchronization controller is proposed for the general chaos model. Compared to other results, the controller designed is simpler and independent on the nonlinear function of chaos system. So the finite-time control scheme can be used in a wide range of chaos system. The simulation results are given to illustrate the effectiveness of the finite-time controller and the applicability to security communication system of this synchronization scheme.

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Design of Finite-Time Synchronization Controller and Its Application to Security Communication System

Based on the chaos anti-control theory, a new four-dimensional autonomous hyperchaotic system is formulated by adding a periodic driving signal rsin(cos(φt)) to the second equation of the three-dimensional autonomous Chen chaotic system in this paper. The basic dynamical behavior of the new hyperchaotic system was not only demonstrated by numerical simulation, but also verified with Lyapunov exponents and bifurcation analysis. The new hyperchaotic system can be periodic, quasi-periodic, chaotic and hyperchaotic with the variation of the parameter φ. It also has broad and stable hyperchaotic region which makes the new hyperchaotic system has a good application prospect.

A New Hyper-Chaos Generated from Chen's System via an External Periodic Perturbation

An efficient image encryption algorithm is proposed, based on image reconstruction using some adjacent pixel characteristics. Since the permutation of sub-images composing of high 4-bits of the original image has a relatively high computational complexity, in the new scheme the permutation of sub-images is performed with low 4-bits instead, which therefore has a lower computational complexity. Experiment has been carried out, showing relatively high efficiency and security of the new cryptosystem.

Hai Yu

Papers

Fractal Color Image Coding Based on Isosceles Triangle Segmentation

Superpixels With Content-Adaptive Criteria

Design of Finite-Time Synchronization Controller and Its Application to Security Communication System

A New Hyper-Chaos Generated from Chen's System via an External Periodic Perturbation

An Efficient Encryption Algorithm Based on Image Reconstruction