基于RSA密码体制的门限代理签名

目前的门限代理签名方案几乎都是基于离散对数问题的,基于RSA密码体制的门限代理签名方案几乎很少。借助简单秘密共享思想构造了一个新的、安全有效的RSA门限代理签名方案,该方案满足门限代理签名方案的安全性的同时,计算量小,易实现。     

基于RSA的（t0，t1，t，n）门限签名方案

本文提出了一个基于RSA的(t0，t1，t，n)门限签名方案。与已有的(t0，t，n)门限签名相比，该方案具备以下优点：(1)基于广泛认可的RSA方案；(2)公钥及签名验证和普通RSA门限签名相同；(3)安全性和效率有所提高。     

基于RSA密码体制的门限代理签名

在一个(t,n)门限代理签名体制中,原始签名者可以将他的签名权利以门限的方式委托给n个代理签名者,至少t个代理签名者合作,可以产生相应的代理签名,而任何少于t个代理签名者则不能.目前已经有很多基于离散对数问题的门限代理签名方案,但是并没有出现一个真正意义上的基于RSA密码体制的门限代理签名方案.鉴于RSA在理论及应用中的重要性,基于RSA构造门限代理签名体制是必要的.文中借助于RSA秘密共享的思想,构造了一个安全、有效的RSA门限代理签名方案.在文中的方案中,没有使用可信权威,所有的秘密参数都是由参与者分布式产生的.     

基于RSA的门限失败-停止签名方案

失败-停止签名是一类不依赖于攻击者计算能力假设的数字签名技术,即使攻击者拥有无限的计算能力,签名者也可以证明一个签名是伪造的。目前,基于RSA密码体制的失败-停止签名已经比较成熟,我们在此基础上提出了一种新的门限失败-停止签名方案,并对此方案进行了安全性分析。该方案基于可证明安全的RSA失败-停止签名,具有欺骗检测（验证部分签名）和能够显示而高效地证明伪造性等特点。     

Shoup门限RSA签名方案的改进

门限签名是对普通数字签名的推广 ,其中签名的生成必须由多个成员合作才能完成 ,但签名的验证只需要知道群体的公开密钥即可进行 .Shoup在 2 0 0 0年的欧洲密码会议上提出了一个切实可行的门限 RSA签名方案 .在此对 Shoup的这一方案作了改进 ,使得改进方案不仅在安全性上与原方案相同 ,而且性能更好 .更为重要的是 ,改进方案还可以扩展到门限不可否认签名的情形 .     

Shuop门限RSA签名方案的改进

门限签名是对普通数字签名的推广，其中签名的生成必须由多个成员合作才能完成，但签名的验证只需要知道群体的公开密钥即可进行，Shoup在2000年的欧洲密码会议上提出了一个切实可行的门限RSA签名方案，在此对Shoup的这一方案作了改进，使得改进方案不仅在安全性上与原方案相同，而且性能更好，更为重要的是，改进方案还可以扩展到门限不可否认签名的情形。     

一种安全的门限代理签名方案

基于离散对数问题和RSA公钥密码体制以及安全的单向函数,提出了一个安全的门限代理签名方案.新方案引入授权文书和时间证书等概念,克服了代理人滥用权力的缺陷,使代理人只能在特定时间内进行次数一定的代理签名;对每个参与者,分配了验证片段,高效解决了参与者的欺诈问题,有效克服了伪造签名攻击和合谋攻击,提高了签名的安全性.分析表明,新方案提高了门限代理签名的安全性,是一个安全可行的具有理论和应用价值的门限代理签名方案.     

一种安全的门限代理签名方案

基于离散对数问题和RSA公钥密码体制以及安全的单向函数,提出了一个安全的门限代理签名方案。新方案引入授权文书和时间证书等概念,克服了代理人滥用权力的缺陷,使代理人只能在特定时间内进行次数一定的代理签名;对每个参与者,分配了验证片段,高效解决了参与者的欺诈问题,有效克服了伪造签名攻击和合谋攻击,提高了签名的安全性。分析表明,新方案提高了门限代理签名的安全性,是一个安全可行的具有理论和应用价值的门限代理签名方案。     

一种门限代理门限签名方案的内部攻击

2005年,Hwang等提出了一个新的（t,n）门限代理（c,m）门限签名方案。在该方案中,只有n个原始签名者中的t或多于t个合作才能授权给m个代理签名者组成的代理群,同时,只有c或多于c个代理签名者合作才能产生门限代理门限签名。与其他门限多代理多签名方案相比,该方案的优点是原始签名者和代理签名者的利益受到公平的保护。但指出Hwang方案存在内部攻击,即在对一个消息的正常签名中,恶意的内部成员能伪造出另一个消息的有效签名。进一步,在分析攻击原因的基础上给出了两种改进方案。     

一种基于RSA安全可行的（t，n）门限签名方案*

分析了大多数RSA门限群签名方案存在的缺陷,RSA的模数是n,φ(n)是秘密参数,参加部分签名的成员无法知晓,求Lagrange相关系数存在困难,也为建立门限RSA密码体制带来困难.提出一种新的方案以克服上述困难,通过求ai无须在求Lagrange相关系数时进行求逆运算,使该方案在保证安全的前提下变得可行实用.     

Less effortful thinking leads to more social networking? The associations between the use of social network sites and personality traits

Social network sites (SNS) have become an important social milieu that enables interpersonal communication by allowing users to share and create information. This study explored the associations between SNS use and personality traits, i.e., need for cognition (NFC) and information and communication technology (ICT) innovativeness. The findings showed that the SNS use had a negative association with NFC and a positive association with ICT innovativeness. Specifically, people who were more likely to engage in effortful thinking used SNS less often, and those who were high in ICT innovativeness used SNS more often. Meanwhile, those who spent more time on SNS were more likely to be multitaskers. Additionally, those who spent more time on SNS also spent more Internet time in general, more online time for study/work and more time in surfing the Web with no specific purpose. This study, which could be a first look at the link between social networking and our thinking, provides evidence for the associations between social media use and personality traits.     

Regulating self-organized collaborative learning: the importance of homogeneous problem perception,immediacy and intensity of strategy use

Very often, university students deliberately form self-organized study groups, e.g. to study collaboratively for an upcoming exam. Yet, very little is known about what regulation problems such self-organized study groups encounter during their learning process and how they try to cope with these problems. Therefore, this study investigates how completely self-organized groups (i.e., non-guided groups outside the classroom that form without external impulse) regulate their collaborative learning process when faced with different kinds of regulation problems. More specifically, we tested the hypotheses that members of self-organized study groups are more satisfied with their group learning experience (a) the more homogeneous their problem perceptions are within their group, (b) the more they apply immediate (rather than non-immediate) strategies to remedy their regulation problems, and (c) the more frequently they apply regulation strategies. In a longitudinal study, N?=?122 students, voluntarily studying for their exams in N?=?52 groups, were asked to indicate the types of problems they experienced, the types of strategies they used to tackle those problems, and their satisfaction with their group learning experience after each of their self-organized study meetings. Hierarchical linear modeling confirmed all hypotheses. Qualitative analysis of two selected groups’ self-reported situational data provided additional insights about the mechanisms that may have contributed to the results. Our study provides important directions for future research, including the recommendation to identify the processes by which groups (a) can reach homogeneity of problem perceptions and (b) coordinate the choice of appropriate strategies within the group.

     

Comparison of linear and nonlinear spectral unmixing approaches: a case study with multispectral TM imagery

Spectral unmixing has been widely used by researchers in quantitative remote sensing due to the prevalence of mixed pixels in low- or middle-resolution images. In this article, six linear and nonlinear unmixing approaches – fully constrained least squares (FCLS), bilinear-Fan model (BFM), polynomial post-nonlinear model (PPNM), supervised fuzzy c-means (SFCM), Support Vector Machine (SVM), and artificial neural network (ANN) – are applied with multispectral Landsat Thematic Mapper (TM) data in order to systematically compare their performance under different scenarios. In addition, a strategy of band selection was proposed for solving the endmember variability issue. The unmixing results were analysed in terms of the overall performance, pure and mixed data set, sub-scenes with different mixture proportions by calculating the accuracy indices: root mean square error (RMSE) and the Pearson correlation coefficient (r). Nonlinear approaches can generate a closer abundance fraction map to reference, and have a higher overall accuracy than the linear approach. Nevertheless, the performance of nonlinear approaches differed dramatically with the increased proportion of mixed pixels in different study areas. SVM, SFCM, BFM, and PPNM depicted a scenario better when the proportion of mixed pixels was high, whereas ANN worked more effectively when processing large amounts of relatively pure pixels (or mixed pixels with large/extreme proportions). The linear approach, in contrast, performed more consistently for various areas. Overall, our study indicates that nonlinear approaches are more effective than the linear one, especially for a study area consisting of different small parcels. The performance of nonlinear approaches is more sensitive to the proportion change of mixed pixels in a study area. The linear approach, however, is more appropriate for a rough estimation, particularly with little prior knowledge of the study area.     

“Clickers” and metacognition: A quasi-experimental comparative study about metacognitive self-regulation and use of electronic feedback devices

The purpose of this study was to establish whether electronic response systems (clickers) influence student metacognition in large lecture settings more than low-technology polling devices. In this first part of a two part mixed methods study inquiry was made into whether student metacognition was influenced and how metacognition was influenced. This quasi-experimental study was performed with students from three sections of the same undergraduate educational psychology course taught by the same instructor. Participants totaled 198: 33 in the summer section, 87 in the fall experimental (clickers) group, and 78 in the fall (paddles) comparison group. Because metacognition is associated with higher academic outcomes, we hypothesized that the response device which elicited higher levels of metacognition would also demonstrate higher performance outcomes. While results from the study indicate that metacognitive processes are influenced more so by paddles than by clickers, clicker use produced significantly higher performance outcomes. Results of this study support recent research findings indicating that higher performance outcomes result when clicker use is combined with instructional strategies; furthermore, findings suggest metacognition from clicker use was a more productive influence on the learning process.     

An experience-based system supporting inventory planning: A fuzzy approach

The study aims to extend the Uncapacitated Fuzzy Single Item Lot Sizing Problem (known as F-USILSP) model and extend it for inventory planning. The F-USILSP model is a good choice when there is no statistical data collection, but where there is verbal or qualitative information from experts with experience. Previously, the mixed integer linear programming (MILP) relied on the crisp assumption which hinders the use of the F-USILSP. In this paper, a Possibility Approach is adapted to convert the F-USILSP to a mathematically solvable equivalent crisp USILSP (EC-USILSP). The EC-USILSP model is tested with a case. The organization under study is a petrochemical company power plant with trapezoidal fuzzy demand and triangular fuzzy unit price. The overall results show that the EC-USILSP is more practical and exhibits more flexibility when there is a need to add more realistic situations.     

The process of team communication in multi-cultural contexts: An empirical study using Bales’ interaction process analysis (IPA)

The main goal of the present study was to empirically investigate the manner in which cultural diversity and communication mode affect team communication process. Two independent variables were manipulated in the study: (1) cultural diversity (homogeneous versus heterogeneous); and (2) communication mode (face-to-face versus computer-mediated communication). Team members’ communication exchanges were measured by using Bales’ interaction process analysis (IPA) that divides the function (as opposed to the topical content) of communication during group discussion into either task-related or socio-emotional contributions at two-levels: communication profile and functional area. Results of this study indicated homogeneous teams used more showing agreement, giving opinions, and showing tension communication patterns compared to heterogeneous teams. Additionally, when considering the higher-level functional areas, teams using face-to-face (FTF) communication strategies were characterized by greater positive socio-emotional communication, more attempted answers, more questions, and more frequent negative socio-emotional communications. The results of the present study also suggested that the impact of communication mode on team communication varies by the level of diversity within the team. The outcomes of this research should have a broad impact on the management of a multi-cultural team, a task-oriented team consisting of people with different national cultures. Relevance to industry: Results of the present study should provide valuable insights into the ways in which cultural diversity and communication mode influence the communication mechanisms which take place among members during team interaction.     

A customer-involved design concept evaluation based on multi-criteria decision-making fusing with preference and design values

Customer-involved design concept evaluation (CDCE) is a key issue for developing new product welcomed by customers, but seldom studies have considered the integrated utilization of objective design values (DVs) and customers’ subjective preference values (PVs). Our previous study has attempted to fuse with DVs and PVs in CDCE, while this is only limit to few situations under benefit-like and cost-like evaluation criteria. For better CDCE, this study further fuses with DVs and PVs in more complex situations, and puts forward an improved version of rough distance to redefined ideal solution (RD-RIS II) in multi-criteria decision-making (MCDM) scope to select the optimal concept. Different from old RD-RIS in previous study, RD-RIS II not only supports the ideal solution definition (ISD) processes for both quantitative and qualitative evaluation criteria, and but more importantly, it utilizes more useful information (value, feature, number and impact) from DVs and PVs to redefine the new positive ideal solution (PIS) and negative ideal solution (NIS). Through the rough distance calculation, the alternative which is close to PIS and far away from NIS is selected as the best one. Besides, the feasibility of RD-RIS II is validated via the application in real design evaluation example, and three empirical comparisons confirm that RD-RIS II makes more comprehensive decision than other MCDM-based evaluation methods, especially when the choices of customers and designers are conflicting, therefore it could provide more reasonable evaluation result which has better credibility and stability than others.     

Are you on Timeline or News Feed? The roles of Facebook pages and construal level in increasing ad effectiveness

This study examines how psychological distance between a user and a Facebook page (Timeline vs. News Feed) impacts the effectiveness of advertising messages framed by two different construal levels (high- vs. low-level construal). Based on construal level theory, a 2 (Psychological distance: distant vs. proximal) × 2 (Message type: high-level vs. low-level construals) factorial design was employed. The results of the study showed that individuals accessing the News Feed page responded more favorably to abstractly framed desirability-focused messages than concretely framed feasibility-focused messages. In contrast, individuals accessing the Timeline page showed more positive reactions to concretely framed feasibility-focused messages compared to abstractly framed desirability-focused messages. The study concludes with the discussions of theoretical and empirical implications and recommendations for future research.     

Program comprehension of domain-specific and general-purpose languages: replication of a family of experiments using integrated development environments

Domain-specific languages (DSLs) allow developers to write code at a higher level of abstraction compared with general-purpose languages (GPLs). Developers often use DSLs to reduce the complexity of GPLs. Our previous study found that developers performed program comprehension tasks more accurately and efficiently with DSLs than with corresponding APIs in GPLs. This study replicates our previous study to validate and extend the results when developers use IDEs to perform program comprehension tasks. We performed a dependent replication of a family of experiments. We made two specific changes to the original study: (1) participants used IDEs to perform the program comprehension tasks, to address a threat to validity in the original experiment and (2) each participant performed program comprehension tasks on either DSLs or GPLs, not both as in the original experiment. The results of the replication are consistent with and expanded the results of the original study. Developers are significantly more effective and efficient in tool-based program comprehension when using a DSL than when using a corresponding API in a GPL. The results indicate that, where a DSL is available, developers will perform program comprehension better using the DSL than when using the corresponding API in a GPL.     

Effect of initial horizontal object position on peak L5/S1 moments in manual lifting is dependent on task type and familiarity with alternative lifting strategies

This study investigated whether the effects of initial horizontal object position on peak L5/S1 total moment (PTM) are affected by task type or familiarity with alternative lifting strategies during manual lifting. Nine subjects lifted low-lying boxes from far and close initial horizontal positions in a typical laboratory lifting task (without any transportation of the load) and in a more realistic lifting task in which the box was transported to a location at a few metres distance. Subsequently, subjects were familiarised with alternative lifting strategies (e.g. shifting and tilting) and they then repeated the more realistic lifting task. Compared with the typical laboratory lifting task, the more realistic lifting task resulted in 6% larger PTMs for the close-positioned box. Familiarisation with alternative lifting techniques resulted in a 10% reduction in PTMs for the far-positioned box. As a result, the effect of initial horizontal box position on PTMs was smaller for the more realistic lifting task than for the typical laboratory lifting task and vanished after familiarisation with alternative lifting strategies. STATEMENT OF RELEVANCE: This study showed that the effect of horizontal box position on peak L5/S1 moments is dependent on the type of lifting task (comparing a typical laboratory simulated lifting task with a more realistic task involving carrying the load for a short distance) and familiarity with alternative lifting strategies. Therefore, it is recommended that back loading should be evaluated in a realistic simulation of the work situation or at the workplace itself.