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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

In this paper, the finite-time control method is proposed to achieve synchronization based on bidirectional coupled chaotic systems. The stability criteria is presented for error system based on Lyapunov method. Compared to other results, the proposed controller is simpler and the new nonlinear system is considered which is consisted of the chaos system and the finite time controller. The Wolf method is used to calculate the largest Lyapunov exponent which shows that the controlled chaos system remains chaotic features. Simulation results for Lorenz system are presented to illustrate the effectiveness of the finite-time synchronization control scheme.

The Bidirectional Coupled Synchronization of Chaotic System Using Finite-time Control

Due to the characteristics of SCADA data, it is difficult, if not impossible, to use data-driven approach to predict wind turbine failures based on SCADA data. In this paper, we take a different tact. Resorting to unsupervised anomaly detection, we could detect suspicious turbine states, which might contain potential approaching failures. After that, a rule based decision maker could decide which redundant anticipatory operations, such as feathering, could eliminate the failures beforehand. Even if there is no failure actually, the redundant operations will not harm the equipment. To build such a system, we just use SCADA data, and do not need to modify the existing equipment. This paper presents the requirements and mechanism of the proposed system, as well as shows the feasibility using a case study about blade breakage.

Redundant Anticipatory Control to Avoid Wind Turbine Failures Based on SCADA Data

CsPbBr3 perovskite nanocrystals have emerged as promising candidates for photocatalysis. However, their conversion efficiency is hampered by material instability, and the accumulation of deactivated perovskites produced after photocatalytic reactions raises significant environmental concerns. To address this issue, we developed a mechanochemical grinding approach assisted by oleylamine as an additive to restore the optical properties and photocatalytic activity of deactivated CsPbBr3, which was due to aggregation in the photocatalytic CO2 reduction reaction. Upon regeneration, the CsPbBr3 nanocrystals exhibited an average length of 34.21 nm and an average width of 20.86 nm, demonstrating optical properties comparable to those of the pristine CsPbBr3 nanocrystals. Moreover, they achieved a conversion efficiency of 88.7% compared with pristine CsPbBr3 nanocrystals in the photocatalytic CO2 reduction reaction. This method effectively enhanced the utilization of CsPbBr3, offering a novel approach for the recycling and recovery of perovskite materials and thereby minimizing material waste and environmental pollution.

Recycling and Recovery of Deactivated CsPbBr3 Perovskite after Photocatalytic CO2 Reduction Reaction.

In this paper, a new scheme that measures the importance of hub streets is proposed, in which the variety of the intersections is investigated based on the topological community structure. The practicality of the proposed methodology is demonstrated through a case study. Simulations have been carried out and analyzed in detail, illustrating the feasibility of the pro-posed scheme.

A new measure to identify the hub in urban traffic networks

Vulnerabilities are known reported security threats that affect a large amount of packages in the npm ecosystem. To mitigate these security threats, the open-source community strongly suggests vulnerable packages to timely publish vulnerability fixes and recommends affected packages to update their dependencies. However, there are still serious lags in the propagation of vulnerability fixes in the ecosystem. In our preliminary study on the latest versions of 356,283 active npm packages, we found that 20.0% of them can still introduce vulnerabilities via direct or transitive dependencies although the involved vulnerable packages have already published fix versions for over a year. Prior study by (Chinthanet et al. 2021) lays the groundwork for research on how to mitigate propagation lags of vulnerability fixes in an ecosystem. They conducted an empirical investigation to identify lags that might occur between the vulnerable package release and its fixing release. They found that factors such as the branch upon which a fix landed and the severity of the vulnerability had a small effect on its propagation trajectory throughout the ecosystem. To ensure quick adoption and propagation of a release that contains the fix, they gave several actionable advice to developers and researchers. However, it is still an open question how to design an effective technique to accelerate the propagation of vulnerability fixes. Motivated by this problem, in this paper, we conducted an empirical study to learn the scale of packages that block the propagation of vulnerability fixes in the ecosystem and investigate their evolution characteristics. Furthermore, we distilled the remediation strategies that have better effects on mitigating the fix propagation lags. Leveraging our empirical findings, we propose an ecosystem-level technique, Plumber, for deriving feasible remediation strategies to boost the propagation of vulnerability fixes. To precisely diagnose the causes of fix propagation blocking, Plumber models the vulnerability metadata, and npm dependency metadata and continuously monitors their evolution. By analyzing a full-picture of the ecosystem-level dependency graph and the corresponding fix propagation statuses, it derives remediation schemes for pivotal packages. In the schemes, Plumber provides customized remediation suggestions with vulnerability impact analysis to arouse package developers’ awareness. We applied Plumber to generating 268 remediation reports for the identified pivotal packages, to evaluate its remediation effectiveness based on developers’ feedback. Encouragingly, 47.4% our remediation reports received positive feedback from many well-known npm projects, such as Tensorflow/tfjs, Ethers.js, and GoogleChrome/workbox. Our reports have boosted the propagation of vulnerability fixes into 16,403 root packages through 92,469 dependency paths. On average, each remediated package version is receiving 72,678 downloads per week by the time of this work.

Hai Yu

Papers

The Bidirectional Coupled Synchronization of Chaotic System Using Finite-time Control

Redundant Anticipatory Control to Avoid Wind Turbine Failures Based on SCADA Data

Recycling and Recovery of Deactivated CsPbBr3 Perovskite after Photocatalytic CO2 Reduction Reaction.

A new measure to identify the hub in urban traffic networks

Plumber: Boosting the Propagation of Vulnerability Fixes in the npm Ecosystem