基于时延Petri网的密码协议分析及性能评估

形式化分析方法由于其精炼、简洁和无二义性逐步成为分析密码协议的一条可靠和准确的途径，但是密码协议的形式化分析研究目前还不够深入，针对这一现状，该文提出用时延Petri网来表示和分析密码协议。该模型不但能够反映协议的静态和动态的特性，而且能够对密码协议进行时间、空间上的性能评估。作为实例，文章对MSR无线协议作了详细的形式分析和性能评估。最后，与其它形式化分析密码协议的方法作了比较。     

Visualizing trace of Java collection APIs by dynamic bytecode instrumentation

Object-oriented languages are widely used in software development to help the developer in using dynamic data structures which evolve during program execution. However, the task of program comprehension and performance analysis necessitates the understanding of data structures used in a program. Particularly, in understanding which application programming interface (API) objects are used during runtime of a program. The objective of this work is to give a compact view of the complete program code information at a single glance and to provide the user with an interactive environment to explore details of a given program. This work presents a novel interactive visualization tool for collection framework usage, in a Java program, based on hierarchical treemap. A given program is instrumented during execution time and data recorded into a log file. The log file is then converted to extensible markup language (XML)-based tree format which proceeds to the visualization component. The visualization provides a global view to the usage of collection API objects at different locations during program execution. We conduct an empirical study to evaluate the impact of the proposed visualization in program comprehension. The experimental group (having the proposed tool support), on average, completes the tasks in 45% less time as compared to the control group (not provided with the proposed tool). Results show that the proposed tool enables to comprehend more information with less effort and time. We have also evaluated the performance of the proposed tool using 20 benchmark software tools. The proposed tool is anticipated to help the developer in understanding Java programs and assist in program comprehension and maintenance by identifying APIs usage and their patterns.     

An Empirical Study of Distributed Application Performance

A major reason for the rarity of distributed applications, despite the proliferation of networks, is the sensitivity of their performance to various aspects of the network environment. We demonstrate that distributed applications can run faster than local ones, using common hardware. We also show that the primary factors affecting performance are, in approximate order of importance: speed of the user's workstation, speed of the remote host (if any), and the high-level (above the transport level) protocols used. In particular, the use of batching, pipelining, and structure in high-level protocols reduces the degradation often experienced between different bandwidth networks. Less significant, but still noticeable improvements result from proper design and implementation of the underlying transport protocols. Ultimately, with proper application of these techniques, network bandwidth is rendered virtually insignificant.     

基于JAVA语言的多态性探讨

多态性是面向对象的重要特性之一。本文就JAVA语言支持的多态性作了深入全面的探讨,还特别提出了抽象类和接口的本质区别;在此基础上,结合例子说明了多态性在程序设计中的应用。     

基于JAVA语言的多态性探讨

多态性是面向对象的重要特性之一。本文就JAVA语言支持的多态性作了深入全面的探讨，还特别提出了抽象类和接口的本质区别；在此基础上，结合例子说明了多态性在程序设计中的应用。     

Performance Impacts of Web-Enabled Retail Services: An Empirical Study

Prior studies suggest that the growth in online retail is attributed to the effective implementation of media-rich and interactive services and functionalities that help overcome the para-social distance between customers and online retail stores. However, few studies have offered empirical evidence that demonstrates the specific impacts these interactive services and functionalities have on the financial performance of online retailers. Using data on the operations and financial performance of the top 500 online retailers in the U.S., this study investigates the impact that website features and functionalities have on sales performance and other intermediate performance measures. Our findings suggest that website features and functionalities have a significant direct impact on sales as well as an indirect impact through intermediate performance measures. Furthermore, our model identifies the specific performance measures that each website feature targets to improve.     

基于身份的密码学算法研究

为解决在有限资源下大量数字证书的管理问题,基于身份的密码学通过公钥密码仅由身份信息计算产生简化了公钥密码管理,该技术可以作为传统公开密钥基础设施的扩展安全机制以增加其便携性。     

基于密码累加器的无状态区块链性能优化

区块链由于其去中心化的特点,被认为是近年来最具颠覆性和革命性的技术创新之一。然而,目前大多数公有链由于数据高度冗余使得区块链系统数据迅速增长,从而造成节点存储资源消耗严重,此外它还存在区块共识成本较高导致系统吞吐量低的问题。针对区块链的可扩展性问题,提出一种适用于智能合约的无状态区块链性能优化方案STiPChain。STiPChain基于密码累加器与可验证计算完成无状态设计,采用RSA累加器生成智能合约的有效性证明实现节点状态数据压缩,同时通过分布式设计将智能合约的有效性证明更新效率优化至常数,极大降低节点对磁盘和内存的需求。在此基础上,STiPChain将区块共识与区块运算解耦,基于可验证计算技术提出新的智能合约执行逻辑和交易验证方案,解决无状态条件下的交易验证与执行问题,有效提高系统吞吐量。实验结果表明,与Ethereum相比,STiPChain无状态区块链性能优化方案将共识节点的存储需求降低了99%,吞吐量提高了1.6～2 500倍。     

基于Petri网的Java多线程程序分析

多线程程序可以更好地利用计算机资源,提高程序运行效率.但是由于多线程执行的不确定性,程序设计中的潜在错误不易被发现.作为系统建模和分析的工具,Petri网适合对具有同步、并发、冲突的离散事件系统进行建模和分析.文中探讨利用Petri网对Java多线程程序建模,并通过分析模型的结构性质和动态性质定位程序设计中的错误.通过对一个多线程程序实例的建模以及对模型的分析,定位了引发错误的原因,并给出了解决方案.从而说明Petri网在分析多线程程序和提高程序稳定性方面具有优越性.     

基于Java技术的网上书店系统的设计与实现

介绍了运用Java技术来设计与实现网上书店电子商务系统，给出了系统的结构、功能以及解决方案的设计，并就共中的关键技术MVC结构设计进行分析，给出了解决方案。     

Performance of the Java security manager

The Java Security Manager is one major security feature of the Java programming language. However, in many Java applications the Security Manager is not enabled because it slows execution time. This paper explores the performance of the Java Security Manager in depth, identifies the permissions with the worst performance and gives advice on how to use the Security Manager in a more efficient way.Our performance test shows that the CPU execution time penalty varies between 5% and 100% per resource access statement. This extreme range is due to the fact that some resource accesses are costly (such as file and socket access) and therefore hide the performance penalty for the access control check almost completely. The time penalty is much more noticeable with access to main memory resources (such as Java objects).In order to achieve reasonable response times, it is of utmost importance to tune garbage collection because the Java Security Manager creates short-lived objects during its permission check. Also, the order of permissions in the policy file can be important.     

Performance Prediction and Analysis of BOINC Projects: An Empirical Study with EmBOINC

Middleware systems for volunteer computing convert a set of computers that is large and diverse (in terms of hardware, software, availability, reliability, and trustworthiness) into a unified computing resource. This involves a number of scheduling policies and parameters, which have a large impact on the throughput and other performance metrics. How can we study and refine these policies? Experimentation in the context of a working project is problematic, and it is difficult to accurately model complex middleware in a conventional simulator. Instead, we use an approach in which the policies being studied are “emulated”, using parts of the actual middleware. In this paper we describe EmBOINC, an emulator based on the BOINC middleware system. EmBOINC simulates a population of volunteered clients (including heterogeneity, churn, availability, and reliability) and emulates the BOINC server components. After describing the design of EmBOINC and its validation, we present three case studies in which the impact of different scheduling policies are quantified in terms of throughput, latency, and starvation metrics.     

基于Java的数据库访问中的性能问题分析与解决

文章通过逐步剖析JDBC访问数据库的机制,深层分析了造成速度瓶颈问题的原因,并提出在现有的Java技术框架下解决这个性能问题的多种思路和方法。     

密码协议的前向保密性研究

基于Diffie-Hellman密钥建立协议的密码协议可以提供前向保密,该文通过分析Diffie-Hellman密钥建立协议获得了其原型,在此基础上给出了一个可以应用于任何非对称密码体制的具有前向保密的密码协议原型,并应用该原型设计了一个具有前向保密的协议。     

基于有限支付API条件下B2B支付实现方案研究

首先对中国B2B电子支付的现状及两种解决方案进行了分析,然后提出了一种基于中国目前银行界可提供的有限功能支付API条件之下的B2B支付实现方案,该方案在一定程度上能够解决目前中国B2B支付面临的跨行支付难,支付效率低等主要问题,是一种可行的解决方案,对中国B2B电子商务的发展具有一定理论和现实上的指导意义。     

一种改进的密码协议形式化模型

多重集重写MSR(multiset rewriting)模型是一种基于多重集重写的协议形式化建模方法.从目前的研究成果来看,该模型并不完善.针对其攻击者模型验证协议存在的不足,对MSR模型进行了改进,并给出了基于MSR模型的秘密性和认证性描述.实践表明,对模型的改进进一步完善了原模型.     

关于网络课程开发的实证研究

随着网络技术与CAI课件的结合,促进了现代远程教育的发展,网络课程成为远程教育的重要组成元素。本文详细论述了网络课程比传统课程所具有的优势,以及网络课程在开发过程中应注意的开发事项。     

An Empirical Study on Voice-Enabled Web Applications

Although most users access Web applications using Web browser interfaces, pervasive computing offers new ways of accessing Internet applications from any device at any location. Pervasive computing technology impacts consumer attitudes, and the authors studied consumers' acceptance rate toward new pervasive interfaces using various attributes and factors. The study was undertaken in Taiwan, with the cellular phone chosen as the pervasive device for accessing an Internet application prototype--a voice-enabled Web system--through voice user interface technology. The study result showed that Handling was the most important factor in using a voice-enabled Web system. The article's findings can help with the design and     

基于Java体系结构的Web服务器性能优化研究

静态Web技术以固定的方式法布信息,限制了系统综合性能的发挥。采用动态Web技术,通过在服务器和客户端两端编程的方法实现对通信双方系统和信息的发布过程的灵活控制,可以在一定程度上提高Web服务的整体性能。通过对Web服务的原理的分析,找出了影响系统性能的关键环节。提出了基于JAVA架构的解决方案,给出了具体优化设计算法,并进行了性能比较和效益的分析评估。理论和实践证明,方案具有较好的适应性和实用价值。