Sharif Digital Repository

In RFIDtags application or sensor network for some hardware constraints we can not use all-purpose crypto systems such as AES,DES.In this applications in trade off between security and efficiency considering inherent limitation،we desire to satisfy moderate level of security.In recent years various lightweight algorithm has been designed.Purpose of this thesis is cryptanalysis on MIBS as a lightweight algorithm.This lightweight block cipher with Feistel structure and data length of 64-bit uses key lengths of 64-bit or 80-bit and consists of 32 rounds.Methods of attacks are differential،impossible differential and differential fault.the results of differential and impossible differential... 

With the remarkable progress in microelectronics and low-power semiconductor technologies, Radio Frequency Identification technology (RFID) has moved from obscurity into mainstream applications, which essentially provides an indispensable foundation to realize ubiquitous computing and machine perception. However, the catching and exclusive characteristics of RFID systems introduce growing security and privacy concerns. These issues are particularly challenging for low-cost RFID systems where tags are extremely resource-constrained, so designing cryptographic algorithms which are optimized to operate in such environments with limited memory, battery supply and computing power become more and... 

To understand the impact of predation by different types of predators on the vole population dynamics,we formulate a three differential equation model describing the population dynamics of voles, the “specialist predator”and the “generalist predator.” First we perform a local stability study of the different steady states of the basic model and deduce that the predation rates of the “specialist” as well as the “generalist” predator are the main parameters controlling the existence/extinction criteria of the concerned populations. Next we analyze the model from a thermodynamic perspective and study the thermodynamic stability of the different equilibria. The analysis revealsthat when the... 

A voting protocol was introduced by Popveniuc in 2006; it is receipt freeness, so appeared to be resistant against the bribed voter. In 2009 Clark using the bribed contract, and attacked to the voting protocol, in the elections by two candidates. He showed that this protocol is not resistant to the bribed voter. In this thesis, we use game theory and graph to extend the bribed contract for n candidates. Thus with the help of a graph, we show that this protocol with any number of candidates, is not resistant to the bribed voter, and we show that by increasing the number of candidates, the resistance of the protocol would be high and if the number of candidates is n, the success rate of this... 

In order to protect the proxy signers’ privacy, many anonymous proxy signature schemes have been proposed. As far as we know, there is no provable secure anonymous proxy signature scheme without random oracles. Because the provable security in the random oracle model has received a lot of criticism, in this thesis, the aim is proposing the first provable secure anonymous proxy signature in the standard model based on existing standard assumptions.It is shown in the standard model that, the proposal is anonymous against full key exposure and existential unforgeable with the computational Diffie Hellman (CDH) and Subgroup Hiding (SGH) assumptions in bilinear groups.To provide anonymity for proxy... 

Electronic voting is one of the applications of electronic systems, in which collection and tallying the votes are performed electronically. In electronic voting systems, cryptography is used to provide security requirements but defects of the cryptography have made the electronic voting protocol designers to use strong assumptions which are impractical or hard to implement.In this research, some of the strong assumptions in electronic voting protocols are studied and the soloution of solving them is given. First, the assumption of trusting to the tally authority in electronic voting protocols which are based on deniable authentications is considered and a new internet voting protocol based... 

Wireless communication networks such as cell phones are rapidly expanding and every day they attract more users. Information flow in these networks is basically through free space. Thus, theses networks are inherently subjected to eavesdropping. Cryptography based on the secure key is the well known traditional way of protecting information security in wireless networks. However, these cryptosystems are just computationally secure and have their vulnerabilities. Information theoretic security is a relatively new method which doesn’t rely on any preshared key or key infrastructure and uses inherent characteristics of the communication channel to provide robust and provable security.In this... 

Fair exchange of digital items through computer network is an important research topic of modern cryptography. Generallty, a fair exchange protocol is a way which helps two parties to exchange their digital items fairly, so that at the end of the protocol execution, both parties recieve their desirable items or none of them recieves anything. In a practical applications, fair exchange protocol is widely used in different but related fields like contract signing protocols,non-repudiation protocols,e-ayment system and certified e-mails. In a fair exchange protocol, a trusted third party (TTP) acts as an arbitrator between two parties. To reduce the traffic load of the arbitrator, the concept... 

Increasing use of World Wide Web and users tend to accompany in the electronic transaction has caused a fair exchange becomes very important and pervasive electronic transaction. These transactions have a lot of usage and benefits. In this study, the optimistic fair exchange has been studied. It is a special case of the fair exchange while having more advantages than the fair exchange. A situation considered that a signer could not sign a message by himself so he delegates his right in signing to a person as a proxy signer. In this study, a protocol of optimistic fair exchange for proxy signature is presented. So, the proxy signer can accompany in the optimistic fair exchange instead of the... 

Increasing demand in power systems necessitates the Generation Expansion Planning (GEP) which is to determine the type, size, and location of new generating units in a planning horizon. The final solution of GEP is based on the minimum cost and/or optimum reliability taking into account various constraints such as capacity of units and lines, operating constraints, and budget restrictions. This paper presents a model based on scenarios for generation expansion planning and units retirement decision. The proposed model could be used by vertically integrated utilities as well as the ISOs in electricity markets to obtain generation expansion schemes. In this approach, uncertainty of units are... 

The current restructuring trend in power industry emplaces the owners and managers under a great pressure to not only reduce the associated investment costs, but also reasonably cut the operation and maintenance expenses as much as possible, while keeping both the power quality and reliability requirements met. Reliability-Centered Maintenance (RCM) has been proved to be in response to this dilemma in power systems since it has been yet successfully applied in various engineering contexts worldwide. This process is more challenging when it comes to the power transmission systems because of its bulkiness and complex structure. On the other hand, market involvement and its intricate behavior... 

Current trend of energy consumption and aging infrastructure of electricity grids mandates high amounts of investment in transmission and distribution networks. On the other hand, with increased awareness about environmental issues, share of renewable energy resources in power generation portfolio has risen in recent years. Microgrids, as one of the most promising solutions to tackle these issues, are able to accommodate high penetration levels of renewable energy sources and distributed generation in distribution systems. However, microgrids sizes are limited due to some operational considerations and as a result, efficient management of distribution systems with high penetration of... 

The main concern of power system planners and operators is to serve electric energy services economically and in an acceptable reliability level. Nowadays, in developing integrated large-scale power networks, reliability evaluation becomes a very tough and time-consuming process. The complexity of this assessment is mainly because of the large number of components, their possible operating states, different faults that can happen, and environmental and other affecting parameters. In power systems, in order to address the complexity, reliability evaluation can be conducted in three different levels. The most complicated study among these three levels is HLII that is so-called composite... 

In the past several decades, with the increasing evolution of electricity markets, maintenance philosophy has gradually changed, and maintenance process plays a crucial role on the profitability and effectiveness of companies. Therefore, this leads managers to use modern strategies that their performance has been proved in various industries and therefore, traditional strategies have lost their effectiveness. Reliability-Centered Maintenance (RCM) is one of the most successful strategies wherein the maintenance process of system components is linked to improvements in the system reliability and profit of companies. RCM has not been thoroughly furnished in generation system yet. This thesis... 

Railroads should be well maintained for safe and efficient operation. The most important reason for the failure of railways is overload and asymmetric load on them. Also, the proper interval for repairs should be adjusted to fit the load crossed over. In order to carry out all these tasks, a constant observation of the weight on the rails must take place. Current dynamic weighing systems are costly. In addition, the installation of these systems is time-consuming and causes permanent damage to the rails. On the other hand, some of the cheaper models of weighing systems require full stop and static weighing, which practically does not work at all, especially on busy rails due to delays. The... 

Virtual power plant (VPP) aggregates the capacity of many diverse distributed energy resources (DERs); it creates a single operating profile from a composite of the parameters characterizing each DER and can incorporate the impact of the network on aggregated DER output. In modern power systems, technical virtual power plants (TVPPs) play an important role enabling presence of DERs in electricity markets. This thesis addresses the optimal bidding strategy problem of a TVPP that participates in the day-ahead (DA) electricity market. TVPP schedules its energy resources in a manner that maximize its profit in DA market. Hence, the optimal schedule of its resources is achieved. In a proposed... 

In recent years, the development of demand response programs with the aim of activating the demand side in order to achieve a wide range of economic and technical benefits in the development of the power system structure has been considered. With the implementation of incentive-based demand response plans, customers receive financial rewards based on changing their load pattern in the favor of electricity companies. However, mid-term and long-term planning to take advantage of this potential requires accurate estimation of the demand response potential in the power system. Also, the value of the baseline load curve of the customers (an estimate of the energy consumption of the customers if... 

According to uncertainty of retailer's customers electricity load and energy price in day-ahead and real-time markets, different scenarios are faced to an electricity retailer. As a result, due to possibility of different scenarios accurance, profit and financial loss of retailer has uncertainty and significant financial risk is imposed to retailer. Electricity retailers for earning the expected profit, reduction ofpossibility of scenarios with little profit (or much loss) and reduction of their risks, use different sources. bilateral contracts, like forward and call option,local wind turbines, distributed generaion, demand response, like load shift and curtailment can be named. This... 

Distribution power systems are undergoing a fundamental transition with the introduction of microgrids (MGs) and proliferation of renewable energy sources inspired mainly by privacy and environmental concerns. In this regard, energy management methods employed by utilities should take into account the intermittent nature of RESs power production while coping with the independent operation of MGs. Transactive energy (TE) is an emerging concept which utilizes economic-based mechanisms to facilitate the dynamic and decentralized management of active agents of the system. However, the energy transactions between transactive agents could have adverse impacts on the technical aspect of the system...