Sharif Digital Repository

Applied pi calculus is a variant of the pi calculus with extensions for modeling cryptographic protocols. In such a calculus, the security guarantees are usually stated as equivalences. While process calculi provide a natural means to describe the protocols themselves, epistemic logics are often better suited for expressing certain security properties such as secrecy and anonymity. These methods studied in this work to investigation the verification of privacy properties in security protocols. And finally, a new approach is introduced to bridge the gap between these two approaches: using the set of traces generated by a process as models. In this method an epistemic logic has constructs for... 

In real life, we can not always expect agents and authorities to have the same desires. Also when it comes to conflicts, agents always tend to break the authorities’ norms to follow their own strategies. Hence we can not expect strict norms to model an actual real life situation.In this article we introduce punishment normative systems, based on multi-agent Marokov chain processes (MMDPs). We try to extend the punishment idea to be also applicable on long-run and infinite strategies. We consider a version of the multi-agent model that is widely used in different situations and then provide an algorithm to find a fair normative system that distributes obligations equally on the agents, while... 

Extensive growth of the internet has had a profound effect on the business environment and rise to a phenomenon known as electronic commerce.electronic commerce has an important role in improvement of organization performance and likewise,has influence in everyday life.despite its name,e commerce is not fully automated.typically,online transactions require a significant level of human intervention.to achieve high degree of automation,we need a new model of software.this model is based upon the notion of agents.agents can act in different stages of e-commerce.one of the most important of these stages is negotiation.negotiation capabilities are essential for e-commerce systems.the agents... 

Agent-Oriented Software Engineering is one of the novel and growing paradigms in computer science, which provides systematic approaches for analysis, designing, implementation and maintenance of multi-agent systems. Agents are the main entities of the agent-oriented software systems. Agents are autonomous and behave flexibly and intelligently. This paradigm is appropriate for developing open, complex, flexible and distributed systems. Design pattern is a general reusable solution to a commonly occurring problem within a specific context in software design. Using patterns in software design has many benefits such as increasing the quality and robustness of the software. Regarding the fact... 

Evolutionary game theory is a relatively new branch of game theory (in contrast to the classical game theory) which has overcome some of the common problems of the classical version such as highly rational agents assumption. Because of this, it has gained popularity among different sciences. On the other hand, social network as one of the branches of complex networks is a pretty novel research area and has application in several fields. Networks are everywhere and most real-world networks are complex ones. Group formation and evolution are among important subjects in studying social networks and some works has been done in analyzing and modeling them. In this thesis we have presented a... 

The auction models are one of the fundamental issues of economics. So far, the bidders were assumed independent of one another in auction models. In this thesis the bidders are considered as a social network. Bidding of an agent influences bidding behavior of other agents based on the network among them. Considering social network among the buyers, we study seller's optimal strategy  

Since the computation of human life is in progress rapidly, we need to offer new concepts in Computational Theory, to obviate these needs. One of these concepts are hypercomputation and hypercomputers, which draw lots of attention in recent years. In this thesis, we study hypercomputaion and hypercomputers in more details.First, we briefly review Computational Theory principles and hypercomputation. After that, we provide and explain about some hypercomputers models and their computational power. After a detail description of interactive computation, as one of the models of hypercomputation, we propose our “Consistent Persistent Turing Machine,” as a model of hypercomputer for interactive... 

Security protocols may be provable secure when used alone, but these protocols lose their security under composition operation. Universal Composition framework (UC) is a tool for analyzing security protocols under composition. UC framework guarantees that the cryptographic protocols keep their security under this composition operation. In this paper we state a modeling for key-evolving signature protocol within the UC framework as a case study. To do this, the ideal functionality is proposed for key-evolving signature scheme that keeps the security requirements of this scheme. Finally, we show that UC definition of security is equivalent to definition of security which is termed here as... 

With the significant advances in software engineering and developing complicated systems, it’s important to investigate the interaction between systems. Agentoriented software engineering is a new paradigm for developing distributed intelligent systems. Agent technology currently plays an important role in complex software development. The underlying paradigm offers a large repertoire of original concepts, architectures, interaction protocols, and methodologies for the analysis and the specification of complex systems built as Multi-Agent Systems (MAS). Several efforts, originating from academia, industry, and several standardisation consortium, have been made in order to provide new tools,... 

Clustering algorithms are developed to provide general attitudes on database, recognizing latent structures and their more effective accessibility. Recently, broad studies are conducted on clustering since it is recognized as an important tool to explore and analyze data. Clustering is a fundamental learning operation without monitoring in data exploration which divides data into groups of objects so that objects in one group have the most similarity to each other and lowest similarity to objects in other groups. Some clustering algorithms such fuzzy clustering model (FCM) are widely used in clustering problem solution although this technique addresses local optimized searches. Additionally,... 

Due to the increase of computer networks and their application, the need for secure communication has become a very important concern. We introduce Cmail, a secure messaging system that works without any central party and in addition protects privacy of users. This system is on top of a cryptocurrency system such as Bitcoin. Bitcoin is cryptocurrency that works on the Internet. The suply of bitcoins and verification of transactions is done by Bitcoin miners, which are some typical client of Bitcoin system, in a decentralizd maner. In Cmail the miners have additional task, they should transfer messages of users and if needed, they hold it for a limited time. In order to increase incentive of... 

Secret sharing is a method for sharing a secret among a number of participants in a manner that an authorized subset of participants can recover the secret using some information, called share, and some public values. One type of secret sharing schemes is Multi-stage Multisecret sharing scheme (MSSS). In such schemes, assigning one share to each participant, an authorized subset of participants is able to recover the secrets in different stages without any information leakage from the recovered secret(s) to the other one(s), using some public information.The number of public values is one of the most important parameters in secret sharing schemes. In this thesis we show that the number of... 

In this thesis, we study monadic second order logic and the languages of graphs. We introduce the notion of ∆- regular graph automaton. Then we designed this finite automaton for processing on labeled graphs. Definability of graph languages which are recognizable by this automaton is shown. To do this, we first briefly introduced monadic second order logic, and then we studied definability of regular string and tree languages in monadic second order logic. In the last section of thesis, ∆- regular graph automaton is introduced  

Housing is one of the important staple goods. The main different between housing market and the other markets is limitation of stock at short term. So it is very important to regularize housing market for apropos accountability and according to society consumption demand. This document introduce the result of an agent based modeling of housing market. There are agents that find out the maximum utility for choosing one of following house related conditions: purchase, sale and lease agreement. In fact in this model people have two phases. The effect of land value taxation for regularization of housing market will analyses with this model. Its seems that by implementation of mentioned tax, the... 

Matching theory plays an important role in analyzing economic behavior in social networks. The matching theory has application in marriage problems, kidney exchange, allocating workers to firms and etc. The main problem in matching theory is to design a mechanism such that it results in maximizing the welfare and it is incentive compatible, to tell the truth for each individual. In this thesis, we introduce a measure for comparing any two matchings and we investigate two matchings mechanisms under certain domains  

One of the biggest challenges in online communication is privacy of individuals. Although anonymous communication (AC) protocols has been the subject of several security and anonymity analyses recently, there are still few frameworks for analyzing such complex systems (e.g. Tor) and their anonymity properties in a unified manner. In this study, an overview of anonymity features and techniques will be discussed by examining various protocols that provide undetectable network communication. Afterwards, the Tor network is described more precisely. Furthermore, the literature of formal methods is briefly reviewed, and the Universal Composable (UC) framework for the analysis of cryptography... 

Epistemic algorithms are instructions and rules based on knowledge of agents. These algorithms by individual or group knowledge of agents make decisions about future behavior of systems. Epistemic gossip protocols is one of these algorithms. They are used to for spreading secrets among nodes in a network. According to individual knowledge of each node they decide who calls whom in each step. In security problems epistemic algorithms are used to detect the safety of protocols. Some epistemic notions like ignorance and contingency are used in formalization of security problems. In the thesis we study these epistemic algorithms  

The quality is the last word of customer satisfaction concept. The structure and the main goal of many of large and small companies have been formed with systems aggregate related to process and product quality. Whereas quality is not achieved only under the protection of inspecting and controlling, then the quality management standards have been designed and produced to control all the activities and organization effective processes. Quality management standards in auto industries have been developed with increasing of customer desire and their severity simultaneously. Which the set of some standards such as ISO 9000, QS 9000, VDA, … and the most ISO TS 16949 requirements have been used....