Contrairement aux protocoles cryptographiques fondés sur la théorie des nombres, les systèmes de chiffrement basés sur les codes correcteurs d’erreurs semblent résister à l’émergence des ordinateurs quantiques. Un autre avantage de ces systèmes est que le chiffrement et le déchiffrement sont très rapides, environ cinq fois plus rapide pour le chiffrement, et 10 à 100 fois plus rapide pour le déchiffrement par rapport à RSA. De nos jours, l’intérêt de la communauté scientifique pour la cryptographie basée sur les codes est fortement motivé par la dernière annonce de la “National Institute of Standards and Technology" (NIST), qui a récemment initié le projet intitulé “Post-Quantum cryptography Project". Ce projet vise à définir de nouveaux standards pour les cryptosystèmes résistants aux attaques quantiques et la date limite pour la soumission des cryptosystèmes à clé publique est fixée pour novembre 2017. Une telle annonce motive certainement à proposer de nouveaux protocoles cryptographiques basés sur les codes, mais aussi à étudier profondément la sécurité des protocoles existants afin d’écarter toute surprise en matière de sécurité. Cette thèse suit cet ordre d’idée en étudiant la sécurité de plusieurs protocoles cryptographiques fondés sur la théorie des codes correcteurs d’erreurs. Nous avons commencé par l’étude de la sécurité d’une version modifiée du cryptosystème de Sidelnikov, proposée par Gueye et Mboup [GM13] et basée sur les codes de Reed-Muller. Cette modification consiste à insérer des colonnes aléatoires dans la matrice génératrice (ou de parité) secrète. La cryptanalyse repose sur le calcul de carrés du code public. La nature particulière des codes de Reed-Muller qui sont définis au moyen de polynômes multivariés binaires, permet de prédire les valeurs des dimensions des codes carrés calculés, puis permet de récupérer complètement en temps polynomial les positions secrètes des colonnes aléatoires. Notre travail montre que l’insertion de colonnes aléatoires dans le schéma de Sidelnikov n’apporte aucune amélioration en matière de sécurité. Le résultat suivant est une cryptanalyse améliorée de plusieurs variantes du cryptosystème GPT qui est un schéma de chiffrement en métrique rang utilisant les codes de Gabidulin. Nous montrons qu’en utilisant le Frobenius de façon appropriée sur le code public, il est possible d’en extraire un code de Gabidulin ayant la même dimension que le code de Gabidulin secret mais avec une longueur inférieure. Le code obtenu corrige ainsi moins d’erreurs que le code secret, mais sa capacité de correction d’erreurs dépasse le nombre d’erreurs ajoutées par l’expéditeur et par conséquent, un attaquant est capable de déchiffrer tout texte chiffré, à l’aide de ce code de Gabidulin dégradé. Nos résultats montrent qu’en fin de compte, toutes les techniques existantes visant à cacher la structure algébrique des codes de Gabidulin ont échoué. Enfin, nous avons étudié la sécurité du système de chiffrement de Faure-Loidreau [FL05] qui est également basé sur les codes de Gabidulin. Inspiré par les travaux précédents et, bien que la structure de ce schéma diffère considérablement du cadre classique du cryptosystème GPT, nous avons pu montrer que ce schéma est également vulnérable à une attaque polynomiale qui récupère la clé privée en appliquant l’attaque d’Overbeck sur un code public approprié. Comme exemple, nous arrivons en quelques secondes à casser les paramètres qui ont été proposés comme ayant un niveau de sécurité de 80 bits. / Contrary to the cryptosystems based on number theory, the security of cryptosystems based on error correcting codes appears to be resistant to the emergence of quantum computers. Another advantage of these systems is that the encryption and decryption are very fast, about five times faster for encryption, and 10 to 100 times faster for decryption compared to RSA cryptosystem. Nowadays, the interest of scientific community in code-based cryptography is highly motivated by the latest announcement of the National Institute of Standards and Technology (NIST). They initiated the Post-Quantum cryptography Project which aims to define new standards for quantum resistant cryptography and fixed the deadline for public key cryptographic algorithm submissions for November 2017. This announcement motivates to study the security of existing schemes in order to find out whether they are secure. This thesis thus presents several attacks which dismantle several code-based encryption schemes. We started by a cryptanalysis of a modified version of the Sidelnikov cryptosystem proposed by Gueye and Mboup [GM13] which is based on Reed-Muller codes. This modified scheme consists in inserting random columns in the secret generating matrix or parity check matrix. The cryptanalysis relies on the computation of the square of the public code. The particular nature of Reed-Muller which are defined by means of multivariate binary polynomials, permits to predict the values of the dimensions of the square codes and then to fully recover in polynomial time the secret positions of the random columns. Our work shows that the insertion of random columns in the Sidelnikov scheme does not bring any security improvement. The second result is an improved cryptanalysis of several variants of the GPT cryptosystem which is a rank-metric scheme based on Gabidulin codes. We prove that any variant of the GPT cryptosystem which uses a right column scrambler over the extension field as advocated by the works of Gabidulin et al. [Gab08, GRH09, RGH11] with the goal to resist Overbeck’s structural attack [Ove08], are actually still vulnerable to that attack. We show that by applying the Frobeniusoperator appropriately on the public key, it is possible to build a Gabidulin code having the same dimension as the original secret Gabidulin code, but with a lower length. In particular, the code obtained by this way corrects less errors than thesecret one but its error correction capabilities are beyond the number of errors added by a sender, and consequently an attacker is able to decrypt any ciphertext with this degraded Gabidulin code. We also considered the case where an isometrictransformation is applied in conjunction with a right column scrambler which has its entries in the extension field. We proved that this protection is useless both in terms of performance and security. Consequently, our results show that all the existingtechniques aiming to hide the inherent algebraic structure of Gabidulin codes have failed. To finish, we studied the security of the Faure-Loidreau encryption scheme [FL05] which is also a rank-metric scheme based on Gabidulin codes. Inspired by our precedent work and, although the structure of the scheme differs considerably from the classical setting of the GPT cryptosystem, we show that for a range of parameters, this scheme is also vulnerable to a polynomial-time attack that recovers the private key by applying Overbeck’s attack on an appropriate public code. As an example we break in a few seconds parameters with 80-bit security claim.

As a consequence to Gilbert and Sullivan's famed Carpet Quarrel, two operettas with decidedly "exotic" themes, The Nautch Girl; or, The Rajah of Chutneypore, and Utopia Limited; or, The Flowers of Progress were presented to London audiences. Neither has been accepted as part of the larger Savoy canon. This thesis considers the conspicuous business atmosphere of their originally performed contexts to understand why this situation arose. Critical social theory makes it possible to read the two documents as overt reflections on British imperialism. Examined more closely, however, the operettas reveal a great deal more about the highly introverted nature of exotic representation and the ambiguous dialogue between race and class hierarchies in late nineteenth-century British society.

Let q be a nontrivial odd prime power, and let 𝑛 ≥ 2 be a natural number with (𝑛, 𝑞) ≠ (2, 3). We characterize the groups 𝑃𝑆𝐿𝑛(𝑞) and 𝑃𝑆𝑈𝑛(𝑞) by their 2-fusion systems. This contributes to a programme of Aschbacher aiming at a simplified proof of the classification of finite simple groups.

International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / The Consultative Committee for Space Data Systems (CCSDS) formulates and publishes recommendations for space data system standards. CCSDS Recommendations define a layered data communications network along the lines of the OSI model. In the space link layer (OSI Data Link layer) fixed length blocks of CCSDS Packets are generated and multiplexed into the data field of Virtual Channel Data Units (VCDUs) in the Virtual Channel Access Sublayer. VCDUs with error correction coding become CVCDUs (coded VCDUs). CVCDUs (or VCDUs) with an attached sync marker become Channel Access Data Units (CADUs) which are transmitted on the Physical Space Channel. This paper discusses AYDIN's DEC012 Data Unit Decoder, a VMEbus circuit card which recovers Virtual Channel Data Units (VCDUs) from corrupted Channel Access Data Units (CADUs) received on the Space Link Subnet of a CCSDS-compatible space datacomm link. The module's design and operation is described along with its use in the X-ray Timing Explorer (XTE) and Tropical Rainfall Measuring Mission (TRMM) science satellite programs run by NASA Goddard Space Flight Center.

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy in the School of Electrical and Information Engineering, 2016 / Reliable and e cient data transmission have been the subject of current research, most especially in realistic channels such as the Rayleigh fading channels. The focus of every new technique is to improve the transmission reliability and to increase the transmission capacity of the communication links for more information to be transmitted. Modulation schemes such as M-ary Quadrature Amplitude Modulation (M-QAM) and Orthogonal Frequency Division Multiplexing (OFDM) were developed to increase the transmission capacity of communication links without additional bandwidth expansion, and to reduce the design complexity of communication systems. On the contrary, due to the varying nature of communication channels, the message transmission reliability is subjected to a couple of factors. These factors include the channel estimation techniques and Forward Error Correction schemes (FEC) used in improving the message reliability. Innumerable channel estimation techniques have been proposed independently, and in combination with di erent FEC schemes in order to improve the message reliability. The emphasis have been to improve the channel estimation performance, bandwidth and power consumption, and the implementation time complexity of the estimation techniques. Of particular interest, FEC schemes such as Reed-Solomon (RS) codes, Turbo codes, Low Density Parity Check (LDPC) codes, Hamming codes, and Permutation codes, are proposed to improve the message transmission reliability of communication links. Turbo and LDPC codes have been used extensively to combat the varying nature of communication channels, most especially in joint iterative channel estimation and decoding receiver structures. In this thesis, attention is focused on using RS codes to improve the message reliability of a communication link because RS codes have good capability of correcting random and burst errors, and are useful in di erent wireless applications. This study concentrates on symbol level soft decision decoding of RS codes. In this regards, a novel symbol level iterative soft decision decoder for RS codes based on parity-check equations is developed. This Parity-check matrix Transformation Algorithm (PTA) is based on the soft reliability information derived from the channel output in order to perform syndrome checks in an iterative process. Performance analysis verify that this developed PTA outperforms the conventional RS hard decision decoding algorithms and the symbol level Koetter and Vardy (KV ) RS soft decision decoding algorithm. In addition, this thesis develops an improved Distance Metric (DM) method of deriving reliability information over Rayleigh fading channels for combined demodulation with symbol level RS soft decision decoding algorithms. The newly proposed DM method incorporates the channel state information in deriving the soft reliability information over Rayleigh fading channels. Analysis verify that this developed metric enhances the performance of symbol level RS soft decision decoders in comparison with the conventional method. Although, in this thesis, the performance of the developed DM method of deriving soft reliability information over Rayleigh fading channels is only veri ed for symbol level RS soft decision decoders, it is applicable to any symbol level soft decision decoding FEC scheme. Besides, the performance of the all FEC decoding schemes plummet as a result of the Rayleigh fading channels. This engender the development of joint iterative channel estimation and decoding receiver structures in order to improve the message reliability, most especially with Turbo and LDPC codes as the FEC schemes. As such, this thesis develops the rst joint iterative channel estimation and Reed- Solomon decoding receiver structure. Essentially, the joint iterative channel estimation and RS decoding receiver is developed based on the existing symbol level soft decision KV algorithm. Consequently, the joint iterative channel estimation and RS decoding receiver is extended to the developed RS parity-check matrix transformation algorithm. The PTA provides design ease and exibility, and lesser computational time complexity in an iterative receiver structure in comparison with the KV algorithm. Generally, the ndings of this thesis are relevant in improving the message transmission reliability of a communication link with RS codes. For instance, it is pertinent to numerous data transmission technologies such as Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), Digital Subscriber Line (DSL), WiMAX, and long distance satellite communications. Equally, the developed, less computationally intensive, and performance e cient symbol level decoding algorithm for RS codes can be use in consumer technologies like compact disc and digital versatile disc. / GS2016

Submitted by Filipe dos Santos (fsantos@pucsp.br) on 2017-08-17T13:31:01Z No. of bitstreams: 1 Carlos Antonio Carneiro Barbosa.pdf: 2499868 bytes, checksum: 9286fd9bcf83dd402b27c8357bc1aff7 (MD5) / Made available in DSpace on 2017-08-17T13:31:01Z (GMT). No. of bitstreams: 1 Carlos Antonio Carneiro Barbosa.pdf: 2499868 bytes, checksum: 9286fd9bcf83dd402b27c8357bc1aff7 (MD5) Previous issue date: 2017-08-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Fundação São Paulo - FUNDASP / The purpose of this thesis is to construct a proposal for the analysis of the power relations, induced especially after the début of the IURD´s New Temple of Solomon, in the city of São Paulo, in July 2014. Given the prevalence of the theme, it implies, firstly, that an Interpretative Sociology of Power Game, as an initial contribution, can avail itself of contiguous conceptualizations to the work of Pierre Bourdieu. The theory of power or the symbolic game translated sociologically into "spaces of dispute and power game"; parallels in analytical key instances to the characterization of the surrounding mythical environment to the Temple of Solomon. We also work with the possibility that the concept of cluster, borrowed from Economics field could better describe certain peculiarities of our object in its relation/imbrication with a throng of other institutions and religious associations; in particular, from other Pentecostal churches of the most diverse denominations located at Av. Celso Garcia, Bairro do Brás, São Paulo, SP and surrounding area. This church passes through the media´s symbolic power construct (imagery) of the Solomon´s Temple, in its Jewish envelopment, undertaken by the whole universal company jointly with its media ecosystem: news networks, multiple channels on the Web, soap opera, cinema, dramatics; By the construction - physical erection of the building itself, mediated by the largest nationally and internationally renowned companies, sectorial focused, while: the largest real estate brokers, the most prominent consulting and audit offices, large contractors and builders, and leading suppliers, thus supporting the entire period from the construction project presentation in 2010 to its opening in 2014 - passing through leadership speeches, launching of the foundation stone, scale model exhibition to the press and to the general public; description of all construction steps, the twelve unofficial inaugurations, the official inauguration and the entire functionality of the enterprise / A realização da presente tese consiste em construir uma proposta de análise das relações de poder deflagradas sobretudo após o début do Novo Templo de Salomão da IURD, na cidade de São Paulo, em julho de 2014. Dada a prevalência da temática, insinua-se, nesse primeiro momento, que uma Sociologia Interpretativa do Jogo de Poder, possa como contributo inicial, valer-se de conceptualizações contíguas à obra de Pierre Bourdieu. A teoria dos jogos ou a metáfora do jogo traduzida sociologicamente em “espaços de disputa e jogo de poder”; paraleliza em instâncias fulcrais analíticas à caracterização do entorno mítico circundante ao Templo de Salomão. Trabalhamos também com a possibilidade de que o conceito de cluster, tomado de empréstimo da Economia, pudesse melhor descrever certas peculiaridades de nosso objeto em sua relação/imbricação com um aglomerado de outras instituições e agremiações religiosas; em especial, de outras igrejas pentecostais das mais diversas denominações presentificadas na Av. Celso Garcia, no Bairro do Brás, São Paulo, SP e entorno. Tal passa pelo constructo simbólico-midiático (imagético) do Templo de Salomão, no seu envoltório judaico, empreendido por toda a empresa universal conjuntamente ao seu ecossistema midiático: agências de notícias, múltiplos canais na Web, teledramaturgia, cinema, teatro; pela construção – erguimento físico do prédio – em si, mediada pelas maiores empresas renomadas nacionalmente e internacionalmente, setorialmente focadas, enquanto: as maiores intermediadoras de negócios imobiliários, os mais destacados escritórios de consultoria e auditoria, grandes empreiteiras e construtoras, e fornecedores de ponta; cobrindo, assim, todo o transcurso desde a apresentação do projeto de construção no ano de 2010 a sua inauguração em 2014 – passando pelos discursos da liderança, lançamento da pedra fundamental, exposição da maquete à imprensa e ao público em geral; descrição de todas as fases da construção, das doze cerimônias inaugurais não oficiais, da inauguração oficial e da plena funcionalidade do empreendimento

No description available.

This study explores the reflective experiences of indigenous field researchers who were involved in conducting the first population representative research study on gender-based violence and child abuse in the Solomon Islands. The purpose of this thesis study was to gain an understanding and insight into the field researchers’ perceptions of the positive and negative impacts such involvement may have had on their lives. The term ‘impact’ was applied holistically and focus was given to whether negative impacts were mitigated by the positive benefits that may be present from being involved in such research. The research study design was exploratory and qualitative in nature, underpinned by a phenomenological approach. The participants were 29 Solomon Island women who had been employed in the role of ‘field researcher’ for the Solomon Island Family Health and Safety Study. Data collection methods included the use of both in-depth interviews and focus group discussions. Eleven interviews were conducted using a semi-structured approach. Three focus group discussions were facilitated, with the assistance of an open-ended questionnaire guideline. The findings identified a number of themes that emerged from the data collected. The themes highlighted primary impacts that included an emotional, physical and life-changing dimension. There was a pattern where different themes were more prevalent, dependent on what phase of the ‘research journey’ that the researchers’ were reflecting on. A significant finding was that although field researchers’ primarily reported negative impacts, they all unanimously stated that they would be interested in being involved in conducting research on violence against women and children in the future. These findings not only suggest that the positive benefits from being involved in such research mitigated the many negative impacts as reported by the field researchers, but also suggest that through being involved with such research, they developed an increased commitment within their own communities to assist in reducing violence against women and children. Conducting research on violence against women and children in a developing post-conflict country brings with it many physical and emotional challenges for indigenous field researchers. It is essential that field researchers are provided with considerable support during all phases of the research study. The application of ethical and safety standards needs to reflect the unique characteristics of the country where the study is being conducted, taking into account the situational and ambient dangers that field researchers may be confronted with during their time in the field.

Thesis (M.A.)--University of Alabama at Birmingham, 2007. / Description based on contents viewed Feb. 4, 2008; title from title screen. Includes bibliographical references (p. 69-73).

Thesis (Ph.D.)--Ohio University, August, 2008. / Release of full electronic text on OhioLINK has been delayed until June 30, 2011. Includes bibliographical references (leaves 352-361)