Secure Mobile Agents in Electronic Commerce by Using Undetachable Signatures from Pairings

It is expect that mobile agents technology will bring significant benefits to electronic commerce. But security issues, especially threats from malicious hosts, become a great obstacle of widespread deployment of applications in electronic commerce based on mobile agents technology. Undetachable digital signature is a category of digital signatures to secure mobile agents against malicious hosts. An undetachable signature scheme by using encrypted functions from bilinear pairings was proposed in this paper. The security of this scheme base on the computational intractability of discrete logarithm problem and computational Diffe-Hellman problem on gap Diffle-Hellman group. Furthermore, the scheme satisfies all the requirements of a strong non-designated proxy signature i.e. verifiability, strong unforgeability, strong identifiability, strong undeniability and preventions of misuse. An undetachable threshold signature scheme that enable the customer to provide n mobile agents with ‘shares’ of the undetachable signature function is also provided. It is able to provide more reliability than classical undetachable signatures

Multi-agent system security for mobile communication

This thesis investigates security in multi-agent systems for mobile communication. Mobile as well as non-mobile agent technology is addressed. A general security analysis based on properties of agents and multi-agent systems is presented along with an overview of security measures applicable to multi-agent systems, and in particular to mobile agent systems. A security architecture, designed for deployment of agent technology in a mobile communication environment, is presented. The security architecture allows modelling of interactions at all levels within a mobile communication system. This architecture is used as the basis for describing security services and mechanisms for a multi-agent system. It is shown how security mechanisms can be used in an agent system, with emphasis on secure agent communication. Mobile agents are vulnerable to attacks from the hosts on which they are executing. Two methods for dealing with threats posed by malicious hosts to a trading agent are presented. The rst approach uses a threshold scheme and multiple mobile agents to minimise the eect of malicious hosts. The second introduces trusted nodes into the infrastructure. Undetachable signatures have been proposed as a way to limit the damage a malicious host can do by misusing a signature key carried by a mobile agent. This thesis proposes an alternative scheme based on conventional signatures and public key certicates. Threshold signatures can be used in a mobile agent scenario to spread the risk between several agents and thereby overcome the threats posed by individual malicious hosts. An alternative to threshold signatures, based on conventional signatures, achieving comparable security guarantees with potential practical advantages compared to a threshold scheme is proposed in this thesis. Undetachable signatures and threshold signatures are both concepts applicable to mobile agents. This thesis proposes a technique combining the two schemes to achieve undetachable threshold signatures. This thesis denes the concept of certicate translation, which allows an agent to have one certicate translated into another format if so required, and thereby save storage space as well as being able to cope with a certicate format not foreseen at the time the agent was created

On the value of threshold signatures

Threshold signature schemes are examples of threshold cryptosystems, as introduced by Desmedt, [4]. The purpose of this paper is to present a rather simple alternative to threshold signatures which raises questions about the value of such schemes, at least when applied to the mobile agent scenario

Volunteer computing

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 205-216).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.This thesis presents the idea of volunteer computing, which allows high-performance parallel computing networks to be formed easily, quickly, and inexpensively by enabling ordinary Internet users to share their computers' idle processing power without needing expert help. In recent years, projects such as SETI@home have demonstrated the great potential power of volunteer computing. In this thesis, we identify volunteer computing's further potentials, and show how these can be achieved. We present the Bayanihan system for web-based volunteer computing. Using Java applets, Bayanihan enables users to volunteer their computers by simply visiting a web page. This makes it possible to set up parallel computing networks in a matter of minutes compared to the hours, days, or weeks required by traditional NOW and metacomputing systems. At the same time, Bayanihan provides a flexible object-oriented software framework that makes it easy for programmers to write various applications, and for researchers to address issues such as adaptive parallelism, fault-tolerance, and scalability. Using Bayanihan, we develop a general-purpose runtime system and APIs, and show how volunteer computing's usefulness extends beyond solving esoteric mathematical problems to other, more practical, master-worker applications such as image rendering, distributed web-crawling, genetic algorithms, parametric analysis, and Monte Carlo simulations. By presenting a new API using the bulk synchronous parallel (BSP) model, we further show that contrary to popular belief and practice, volunteer computing need not be limited to master-worker applications, but can be used for coarse-grain message-passing programs as well. Finally, we address the new problem of maintaining reliability in the presence of malicious volunteers. We present and analyze traditional techniques such as voting, and new ones such as spot-checking, encrypted computation, and periodic obfuscation. Then, we show how these can be integrated in a new idea called credibility-based fault-tolerance, which uses probability estimates to limit and direct the use of redundancy. We validate this new idea with parallel Monte Carlo simulations, and show how it can achieve error rates several orders-of-magnitude smaller than traditional voting for the same slowdown.by Luis F.G. Sarmenta.Ph.D

Casual Information Visualization on Exploring Spatiotemporal Data

The goal of this thesis is to study how the diverse data on the Web which are familiar to everyone can be visualized, and with a special consideration on their spatial and temporal information. We introduce novel approaches and visualization techniques dealing with different types of data contents: interactively browsing large amount of tags linking with geospace and time, navigating and locating spatiotemporal photos or videos in collections, and especially, providing visual supports for the exploration of diverse Web contents on arbitrary webpages in terms of augmented Web browsing

The role of aspect in paraphrase operations

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

RÖST OCH INSKRIPTION : Utkast till den inre monologens teckenteori

Uppsatsen Röst och inskription. Utkast till den inre monologens teckenteori kan sammanfattas som ett försök att beskriva och förklara strukturella och funktionella egenskaper hos inre monolog (i engelsk litteratur inner speech), samt relatera dessa egenskaper till ?yttre?, dialogiskt talspråk. En axial grundtanke som löper genom hela undersökningen är att monologen inte utan vidare låter sig reduceras till en enkel formel som ?talspråk minus röst? etc., utan att monologen bör anses betingad av andra lingvistiska förutsättningar, bland vilka frånvaron av fysisk röstbildning bara är en bland flera faktorer

The legal and political philosophy of Ronald Dworkin.

This thesis advances a comprehensive and coherent interpretation of Dworkin's ideas. It considers the main criticisms that have been levelled against them and supplies and considers others, concluding that the interpretation offered here provides, in general, a good defence. The thesis includes a biographical sketch, an evaluation of the context of Dworkinian jurisprudence and an exhaustive bibliography. In addition to the published writings, it draws upon unpublished materials and personal conversations. In particular, it is suggested that standard accounts of Dworkin's work tend to overstress his attacks on positivism. Dworkin is right in his characterisation of the "plain fact" view of law, but Hart's theory can be rescued from the claim that it is a plain fact theory and that it is a "semantic" version of it. Dworkin's claims to objectivity in legal reasoning outside of demonstration are also well-founded and his interpretive analogy with art provides important analytical insights. While the right to be treated with concern and respect is the principle underpinning the ideas of integrity and resources, Dworkin's idea that rights "trump" goals applies only to actual communal practices pursuing such goals. In an ideal World, Dworkin is right to abandon welfare as a metric of distribution, but his use of the alternative metric of resources does not strictly follow from the collapse of equality of welfare. Nevertheless, his resources analysis supports the intuition that economic analysis is relevant to legal argument. Further, given the role of resources, it is natural that Dworkin should assert liberty to be part of the market baseline governing distribution. Finally, Dworkin is right to view communitarian duties as continuous with personal ethics but there are problems in his denial of the idea, implicit in Rawls, that justice is an interpretive concept