846 resultados para secure routing protocols


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A novel cryptography method based on the Lorenz`s attractor chaotic system is presented. The proposed algorithm is secure and fast, making it practical for general use. We introduce the chaotic operation mode, which provides an interaction among the password, message and a chaotic system. It ensures that the algorithm yields a secure codification, even if the nature of the chaotic system is known. The algorithm has been implemented in two versions: one sequential and slow and the other, parallel and fast. Our algorithm assures the integrity of the ciphertext (we know if it has been altered, which is not assured by traditional algorithms) and consequently its authenticity. Numerical experiments are presented, discussed and show the behavior of the method in terms of security and performance. The fast version of the algorithm has a performance comparable to AES, a popular cryptography program used commercially nowadays, but it is more secure, which makes it immediately suitable for general purpose cryptography applications. An internet page has been set up, which enables the readers to test the algorithm and also to try to break into the cipher.

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This graduate study was assigned by Unisys Oy Ab. The purpose of this study was to find tools to monitor and manage servers and objects in a hosting environment and to remotely connect to the managed objects. Better solutions for promised services were also researched. Unisys provides a ServerHotel service to other businesses which do not have time or resources to manage their own network, servers or applications. Contracts are based on a Service Level Agreement where service level is agreed upon according to the customer's needs. These needs have created a demand for management tools. Unisys wanted to find the most appropriate tools for its hosting environment to fulfill the agreed service level with reasonable costs. The theory consists of literary research focusing on general agreements used in the Finnish IT business, different types of monitoring and management tools and the common protocols used inthem. The theory focuses mainly on the central elements of the above mentioned topics and on their positive and negative features. The second part of the study focuses on general hosting agreements and what management tools Unisys has selected for hosting and why. It also gives a more detailed account of the hosting environment and its features in more detail. Because of the results of the study Unisys decided to use Servers Alive to monitor network and MS applications’ services. Cacti was chosen to monitor disk spaces, which gives us an idea of future disk growth. For remote connections the Microsoft’s Remote Desktop tool was the mostappropriate when the connection was tunneled through Secure Shell (SSH). Finding proper tools for the intended purposes with cost-conscious financial resources proved challenging. This study showed that if required, it is possible to build a professional hosting environment.

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This Thesis Work will concentrate on a very interesting problem, the Vehicle Routing Problem (VRP). In this problem, customers or cities have to be visited and packages have to be transported to each of them, starting from a basis point on the map. The goal is to solve the transportation problem, to be able to deliver the packages-on time for the customers,-enough package for each Customer,-using the available resources- and – of course - to be so effective as it is possible.Although this problem seems to be very easy to solve with a small number of cities or customers, it is not. In this problem the algorithm have to face with several constraints, for example opening hours, package delivery times, truck capacities, etc. This makes this problem a so called Multi Constraint Optimization Problem (MCOP). What’s more, this problem is intractable with current amount of computational power which is available for most of us. As the number of customers grow, the calculations to be done grows exponential fast, because all constraints have to be solved for each customers and it should not be forgotten that the goal is to find a solution, what is best enough, before the time for the calculation is up. This problem is introduced in the first chapter: form its basics, the Traveling Salesman Problem, using some theoretical and mathematical background it is shown, why is it so hard to optimize this problem, and although it is so hard, and there is no best algorithm known for huge number of customers, why is it a worth to deal with it. Just think about a huge transportation company with ten thousands of trucks, millions of customers: how much money could be saved if we would know the optimal path for all our packages.Although there is no best algorithm is known for this kind of optimization problems, we are trying to give an acceptable solution for it in the second and third chapter, where two algorithms are described: the Genetic Algorithm and the Simulated Annealing. Both of them are based on obtaining the processes of nature and material science. These algorithms will hardly ever be able to find the best solution for the problem, but they are able to give a very good solution in special cases within acceptable calculation time.In these chapters (2nd and 3rd) the Genetic Algorithm and Simulated Annealing is described in details, from their basis in the “real world” through their terminology and finally the basic implementation of them. The work will put a stress on the limits of these algorithms, their advantages and disadvantages, and also the comparison of them to each other.Finally, after all of these theories are shown, a simulation will be executed on an artificial environment of the VRP, with both Simulated Annealing and Genetic Algorithm. They will both solve the same problem in the same environment and are going to be compared to each other. The environment and the implementation are also described here, so as the test results obtained.Finally the possible improvements of these algorithms are discussed, and the work will try to answer the “big” question, “Which algorithm is better?”, if this question even exists.

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In this paper we describe a new protocol that we call the Curry-Howard protocol between a theory and the programs extracted from it. This protocol leads to the expansion of the theory and the production of more powerful programs. The methodology we use for automatically extracting “correct” programs from proofs is a development of the well-known Curry-Howard process. Program extraction has been developed by many authors, but our presentation is ultimately aimed at a practical, usable system and has a number of novel features. These include 1. a very simple and natural mimicking of ordinary mathematical practice and likewise the use of established computer programs when we obtain programs from formal proofs, and 2. a conceptual distinction between programs on the one hand, and proofs of theorems that yield programs on the other. An implementation of our methodology is the Fred system. As an example of our protocol we describe a constructive proof of the well-known theorem that every graph of even parity can be decomposed into a list of disjoint cycles. Given such a graph as input, the extracted program produces a list of the (non-trivial) disjoint cycles as promised.

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The Short-term Water Information and Forecasting Tools (SWIFT) is a suite of tools for flood and short-term streamflow forecasting, consisting of a collection of hydrologic model components and utilities. Catchments are modeled using conceptual subareas and a node-link structure for channel routing. The tools comprise modules for calibration, model state updating, output error correction, ensemble runs and data assimilation. Given the combinatorial nature of the modelling experiments and the sub-daily time steps typically used for simulations, the volume of model configurations and time series data is substantial and its management is not trivial. SWIFT is currently used mostly for research purposes but has also been used operationally, with intersecting but significantly different requirements. Early versions of SWIFT used mostly ad-hoc text files handled via Fortran code, with limited use of netCDF for time series data. The configuration and data handling modules have since been redesigned. The model configuration now follows a design where the data model is decoupled from the on-disk persistence mechanism. For research purposes the preferred on-disk format is JSON, to leverage numerous software libraries in a variety of languages, while retaining the legacy option of custom tab-separated text formats when it is a preferred access arrangement for the researcher. By decoupling data model and data persistence, it is much easier to interchangeably use for instance relational databases to provide stricter provenance and audit trail capabilities in an operational flood forecasting context. For the time series data, given the volume and required throughput, text based formats are usually inadequate. A schema derived from CF conventions has been designed to efficiently handle time series for SWIFT.

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O tema central dessa pesquisa é identificar gargalos da legislação brasileira por meio de revisão das principais leis, decretos e instruções normativas que norteiam o ambiente regulatório para os biofertilizantes, e propor medidas que facilitem o desenvolvimento do setor. O insumo faz parte da legislação brasileira desde a publicação da primeira lei de fertilizantes em 1980, e tem seu uso descrito em trabalhos acadêmicos. No entanto, a falta de registros de produtos biofertilizantes junto ao Ministério da Agricultura, Pecuária e Abastecimento (MAPA) até o final do ano de 2014 merece atenção do setor de insumos e das lideranças que legislam. O entendimento das implicações e efeitos da legislação na adoção do insumo, bem como as implicações para a revisão das normas, presentes no trabalho, apoiam o setor de insumos, as lideranças políticas e a pesquisa na adequação das normas e procedimentos técnicos que viabilizem o registro das soluções do setor de biofertilizantes e o acesso facilitado por parte dos agricultores. O trabalho revisou a legislação brasileira relevante para o insumo biofertilizante, e entrevistou lideranças políticas, institucionais e de empresas no que diz respeito às principais dificuldades enfrentadas para o melhor desenvolvimento do setor. Investigou-se também a situação apresentada em outros países, como Estados Unidos, Canadá e países da União Européia através da revisão de leis e documentos, e de entrevistas com profissionais do setor de insumos e representantes de instituições atuantes nos mercados mencionados. Apesar de diferenças nas definições propostas pelos vários países e outras classificações congruentes, as dificuldades que empresas do setor de nutrição enfrentam no registro de biofertilizantes correspondem aos desafios também enfrentados por empresas para criar a classe de bioestimulantes nos Estados Unidos, e principalmente àqueles da maioria dos países europeus analisados. Identificou-se que a legislação vigente e sua interpretação, e exigências para o lançamento de novos produtos não atendem plenamente o setor produtor de biofertilizantes, o qual ademais não possui a mesma expertise regulatória que o setor agroquímico para melhor definir seus protocolos de validação junto ao órgão anuente. Mudanças na legislação, melhor articulação da cadeia produtiva no entendimento das necessidades, e maior interação das entidades representativas com o Ministério da Agricultura, Pecuária e Abastecimento (MAPA) se fazem essenciais para viabilidade do insumo biofertilizante.

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