DES加密算法及C语言实现

在对称密码体制中,发收双方使用相同密钥,有着同样的加密密钥和解密密钥。在众多的加密算法中影响最大的是DES加密算法。本文详细介绍了DES加密的过程及其C语言实现。     

AES算法的分析与研究

随着计算机和通信技术的发展,用户对信息的安全存储、安全处理和安全传输的需求越来越迫切,随着攻击手段的日益提高和计算机计算速度的增长,原有的DES密码体制由于密钥长度太短,无法满足需要的安全强度。最新的密码体制AES具有简洁、实现速度快、安全性高等优点,是分组密码加密体制的一个相当好的标准。随着AES的确定,分组密码算法的研究越来越受到人们的重视。分组密码具有速度快、易于标准化和便于软硬件实现等特点,通常是信息与网络安全中实现数据加密、数字签名、认证及密钥管理的核心体制,它在计算机通信和信息系统安全领域有着最广泛的应用。本文重点介绍了高级加密标准算法,研究分析了AES加密和解密原理。     

基于嵌入式平台的分布式密钥加解密加载数据的方法

<正>在电子设备上PowerPC与可拆卸存储设备互联的硬件构型下,本文提出合理的加载数据的加解密方法。该方法的核心是密钥分布式存储。通过密钥管理机使用一级密钥加密随机二级密钥得到三级密钥。使用二级密钥加密加载数据。通过网络将加载的数据,三级密钥均分布在可拆卸存储设备上不同分区。PowerPc通过读取加密的数据、三级密钥,使用一级密钥及对称解密算法对加密的三级密钥进行解密得到二级密钥,再使用二级密钥对加载的数据进行解密。使用的加解密算法为256位的AES。     

基于Logistic映射的动态密钥加密算法

混沌序列具有类随机性、对初始条件极度敏感性、遍历性和非周期性等特点,展现出优良的密码学性能。该加密算法通过Logistic映射产生混沌序列,并将混沌序列映射为64位二进制序列,结合DNA序列变迁重组算法和DES算法对64位明文分组进行加密,DES初始密钥处于动态变化中,能有效地抵御穷举攻击和选择密文攻击等多种攻击手段。     

电子商务中的数据加密技术

叙述了数据加密系统的组成，比较了对称密钥加密体制和公开密钥加密体制的优,工得出在电子商务中采用混合密钥加密体制，既保证了数据安全，又提高了加密和解密速度。     

Hill密码中剩余阵的逆矩阵的求法及Matlab实现

在计算机网络中,为了保证数据的保密性和可靠性,需要对数据进行加密与解密。本文先介绍了Hill密码算法,指出Hill密码密钥矩阵即剩余阵的逆矩阵存在的充要条件,最后较详细讨论了求剩余阵的逆矩阵的算法及其Matlab程序,从而可通过Hill密码对信息进行快速加密与解密,实现用户信息安全保护。     

保护文件传输中DES加密算法在数据安全中的应用

随着经济的发展和技术的进步,网络技术的应用日趋广泛,网络文件传输是否安全越来越被人们所重视。对于DES算法来说,如果是原始的算法在一次加密算法中只能处理64位。在本文中使用C语言来加密DES数据,以此来加解密任何大小和格式的数据文件,让文件传输的安全性得到保证。     

基于RSA和高级数据加密标准的网络数据加密方案

阐述了公开密钥密码技术RSA算法和最新的数据加密标准AES,利用AES算法的效率以及DES算法中密钥产生和管理的方便性等特点。并将两者结合起来,提出了一种新的网络数据加密方案,该网络数据加密方案可以有效地解决数据在网络传输中的保密性等问题。     

基于国密SM4和SM2的混合密碡算法研究与实现

现代密码技术在保证信息安全中起着至关重要的作用。SM4算法运算速度快,但存在密钥管理复杂并且安全性低的缺点;SM2算法安全性高、密钥管理简单,但存在对大块数据加解密速度慢和效率较低的缺点。提出一种基于SM4和SM2算法的混合加密算法,大量的主体明文数据采用加密速度极快的SM4算法,利用SM2算法加密SM4算法的密钥并和密文一起传输来避免SM4复杂的密钥管理,提高了数据安全性。经理论分析及在同方THD86芯片上的实验验证,该算法方便可行,加密、解密速度快且安全性高,在电子商务和电子政务中的应用具有良好的效果。     

三阶魔方旋转加密解密文件算法的设计与实现

本文基于三阶魔方“变换数据位置”加密算法,按自定规则旋转魔方,进而实现加密解密。主要算法过程：按54字节对文件顺序分组,对每组信息形成的虚拟数字魔方,按密码映射规则旋转置乱,实现文件加密。按加密反序逆向旋转置位魔方,实现文件解密。其特点是：原理简单,实现容易,运行高效,数据量小,可加密解密任何类型文件。     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.     

Cooler temperatures inductive to locust outbreaks

Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.     

Rough Justice: A Statistical Assessment of ICANN's Uniform Dispute Resolution Policy

Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP.     

Prevalence of soft neurological signs in Chinese people

Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.     

Molecular motor assembly of a biomimetic system

Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.     

Monoculture Rubber Plantations Have Negative Ef ects on Controlling Splash Erosion

<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence