175 resultados para Vigenere cipher


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Mode of access: Internet.

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-Pt. 1. Explanation of the number code, [by] S. C. Chandler, and J. Ritchie.-Pt. 1a. Number code, compiled by John Ritchie. 1885.-Pt.2 Phrase code, [by] S. C. Chandler, and J. Ritchie.-Pt. 3. Tables.

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This paper presents a DES/3DES core that will support cipher block chaining (CBC) and also has a built in keygen that together take up about 10% of the resources in a Xilinx Virtex II 1000-4. The core will achieve up to 200Mbit/s of encryption or decryption. Also presented is a network architecture that will allow these CBC capable 3DES cores to perform their processing in parallel.

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The recently introduced approach for Encrypted Image Folding is generalized to make it self-contained. The goal is achieved by enlarging the folded image so as to embed all the necessary information for the image recovery. The need for extra size is somewhat compensated by considering a transformation with higher folding capacity. Numerical examples show that the size of the resulting cipher image may be significantly smaller than the plain text one. The implementation of the approach is further extended to deal also with color images.

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* Work supported by the Lithuanian State Science and Studies Foundation.

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The Self-shrinking p-adic cryptographic generator (SSPCG) is a fast software stream cipher. Improved cryptoanalysis of the SSPCG is introduced. This cryptoanalysis makes more precise the length of the period of the generator. The linear complexity and the cryptography resistance against most recently used attacks are invesigated. Then we discuss how such attacks can be avoided. The results show that the sequence generated by a SSPCG has a large period, large linear complexity and is stable against the cryptographic attacks. This gives the reason to consider the SSPSG as suitable for critical cryptographic applications in stream cipher encryption algorithms.

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The phenomenonal growth of the Internet has connected us to a vast amount of computation and information resources around the world. However, making use of these resources is difficult due to the unparalleled massiveness, high communication latency, share-nothing architecture and unreliable connection of the Internet. In this dissertation, we present a distributed software agent approach, which brings a new distributed problem-solving paradigm to the Internet computing researches with enhanced client-server scheme, inherent scalability and heterogeneity. Our study discusses the role of a distributed software agent in Internet computing and classifies it into three major categories by the objects it interacts with: computation agent, information agent and interface agent. The discussion of the problem domain and the deployment of the computation agent and the information agent are presented with the analysis, design and implementation of the experimental systems in high performance Internet computing and in scalable Web searching. ^ In the computation agent study, high performance Internet computing can be achieved with our proposed Java massive computation agent (JAM) model. We analyzed the JAM computing scheme and built a brutal force cipher text decryption prototype. In the information agent study, we discuss the scalability problem of the existing Web search engines and designed the approach of Web searching with distributed collaborative index agent. This approach can be used for constructing a more accurate, reusable and scalable solution to deal with the growth of the Web and of the information on the Web. ^ Our research reveals that with the deployment of the distributed software agent in Internet computing, we can have a more cost effective approach to make better use of the gigantic scale network of computation and information resources on the Internet. The case studies in our research show that we are now able to solve many practically hard or previously unsolvable problems caused by the inherent difficulties of Internet computing. ^

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Collaborative installation of painting and sculpture with Denise de Cordova. Both artists use a female subject as a recurring metaphor – as cipher, ghost, or nom de plume, and both employ intricately decorated surfaces to allude to ambiguities inherent in using material to speak of ideas.

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Secure transmission of bulk data is of interest to many content providers. A commercially-viable distribution of content requires technology to prevent unauthorised access. Encryption tools are powerful, but have a performance cost. Without encryption, intercepted data may be illicitly duplicated and re-sold, or its commercial value diminished because its secrecy is lost. Two technical solutions make it possible to perform bulk transmissions while retaining security without too high a performance overhead. These are: 1. a) hierarchical encryption - the stronger the encryption, the harder it is to break but also the more computationally expensive it is. A hierarchical approach to key exchange means that simple and relatively weak encryption and keys are used to encrypt small chunks of data, for example 10 seconds of video. Each chunk has its own key. New keys for this bottom-level encryption are exchanged using a slightly stronger encryption, for example a whole-video key could govern the exchange of the 10-second chunk keys. At a higher level again, there could be daily or weekly keys, securing the exchange of whole-video keys, and at a yet higher level, a subscriber key could govern the exchange of weekly keys. At higher levels, the encryption becomes stronger but is used less frequently, so that the overall computational cost is minimal. The main observation is that the value of each encrypted item determines the strength of the key used to secure it. 2. b) non-symbolic fragmentation with signal diversity - communications are usually assumed to be sent over a single communications medium, and the data to have been encrypted and/or partitioned in whole-symbol packets. Network and path diversity break up a file or data stream into fragments which are then sent over many different channels, either in the same network or different networks. For example, a message could be transmitted partly over the phone network and partly via satellite. While TCP/IP does a similar thing in sending different packets over different paths, this is done for load-balancing purposes and is invisible to the end application. Network and path diversity deliberately introduce the same principle as a secure communications mechanism - an eavesdropper would need to intercept not just one transmission path but all paths used. Non-symbolic fragmentation of data is also introduced to further confuse any intercepted stream of data. This involves breaking up data into bit strings which are subsequently disordered prior to transmission. Even if all transmissions were intercepted, the cryptanalyst still needs to determine fragment boundaries and correctly order them. These two solutions depart from the usual idea of data encryption. Hierarchical encryption is an extension of the combined encryption of systems such as PGP but with the distinction that the strength of encryption at each level is determined by the "value" of the data being transmitted. Non- symbolic fragmentation suppresses or destroys bit patterns in the transmitted data in what is essentially a bit-level transposition cipher but with unpredictable irregularly-sized fragments. Both technologies have applications outside the commercial and can be used in conjunction with other forms of encryption, being functionally orthogonal.

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Na sociedade moderna, o uso de novas tecnologias e das correspondentes aplicações informáticas, levanta diversas questões, sendo, sem dúvida a mais importante, a segurança dos utilizadores e dos sistemas. A implementação de novos processos fazendo uso dos meios informáticos disponíveis permite o aumento da produtividade e a sua simplificação sem perder a fiabilidade, através da desmaterialização, desburocratização, acessibilidade, rapidez de execução, comodidade e segurança. A introdução do cartão de cidadão com todas a sua potencialidade contribui para a implementação dos processos acima referidos, os quais acompanharam a evolução do quadro legislativo nacional e europeu. Contudo verificam-se algumas lacunas, devido à sua imaturidade, sendo o seu desenvolvimento um processo ainda em curso. Com o presente trabalho pretende-se criar uma solução aberta a várias aplicações, que permite a optimização de processos através da sua simplificação, com recurso à assinatura digital, autenticação e uso de dados pessoais, tendo em atenção a legislação vigente, o actual cartão de cidadão e os requisitos de segurança. ABSTRACT: ln modern society, the increasing application of information technologies have arisen several questions, being the private and sensitive data security the most important. Today new informatics processes have come to increase productivity using faster and simplified mechanisms, keeping reliability and security. The introduction in Portugal, of the new citizen card is a great example of the above mentioned, in accordance with the National and European legislation. Nevertheless, being recently adopted, it stills vulnerable and therefore is in constant update and revision. The purpose of this thesis is the creation of an open solution to other new applications, aiming a simplification and optimization of citizen card. Seeking the maximum security, it is utilized digital signature, authentication and personal details, always according to the legislation in effect.