Actuellement, nous vivons dans une société numérique. L'avènement de l'Internet et l'arrivée du multimédia et des supports de stockage numériques, ont transformé profondément la façon dont nous communiquons. L'image en particulier occupe une place très importante dans la communication interpersonnelle moderne. Toutefois, elle présente l'inconvénient d'être représentée par une quantité d'information très importante. De ce fait, la transmission et le stockage des images soulèvent certains problèmes qui sont liés essentiellement à la sécurité et à la compression d'images. Ce sont ces considérations qui ont guidé cette thèse. En effet, la problématique que nous posons dans cette thèse est de proposer une solution conduisant à la crypto-compression d'images afin d'assurer un archivage et un transfert sécurisés tout en conservant les performances de la méthode de compression utilisée. En effet, nos travaux de recherche ont porté essentiellement sur la compression et le cryptage des images numériques. Concernant la compression, nous avons porté un intérêt particulier au codage arithmétique vu sont efficacité en terme de ta ux de compression et son utilisation par les nouvelles normes et standards de compression tel que JPEG2000, JBIG, JBIG2 et H.264/AVC. Quant au cryptage, nous avons opté pour l'utilisation du chaos combiné avec les fractions continues afin de générer des flux de clés ayant à la fois de bonnes propriétés cryptographiques et statistiques. Ainsi, nous avons proposé deux nouvelles méthodes de compression sans perte basées sur le codage arithmétique tout en introduisant de nouveaux paramètres de codage afin de réduire davantage la taille en bits des images compressées. Deux autres méthodes s'appuient sur l'utilisation du chaos et des fractions continues pour le développement d'un générateur de nombres pseudo-aléatoires et le cryptage par flot d'images. Enfin, nous proposons une nouvelle méthode qui emploie conjointement le cryptage avec la compression. Cette dernière méthode se base sur l'échange des sous-intervalles associés aux symboles d'un codeur arit hmétique binaire de façon aléatoire tout en exploitant notre générateur de nombres pseudo-aléatoire. Elle est efficace, sécurisée et conserve le taux de compression obtenu par le codage arithmétique et ceci quelque soit le modèle statistique employé : statique ou adaptatif. / Actually, we live in a digital society. The proliferation of the Internet and the rapid progress in information technology on multimedia, have profoundly transformed the way we communicate. An enormous amount of media can be easily exchanged through the Internet and other communication networks. Digital image in particular occupies an important place in modern interpersonal communication. However, image data have special features such as bulk capacity. Thus, image security and compression issues have became exceptionally acute. It is these considerations that have guided this thesis. Thus, we propose throw this thesis to incorporating security requirements in the data compression system to ensure reasonable security without downgrading the compression performance.For lossless image compression, we have paid most attention to the arithmetic coding (AC) which has been widely used as an efficient compression algorithm in the new standards including JBIG, JBIG2, JPEG2000 and H.264/AVC. For image encryption, we are based on the combination of a chaotic system and the Engel continued fraction map to generate key-stream with both good chaotic and statistical properties. First, we have proposed two new schemes for lossless image compression based on adding new pre-treatment steps and on proposing new modeling methods to estimate probabilities for AC. Experimental results demonstrate that the proposed schemes give mean compression ratios that are significantly higher than those by the conventional AC. In addition, we have proposed a new pseudo-random bit generator (PRBG). The detailed analysis done by NIST statistical test Suite demonstrates that the proposed PRGB is suitable for cryptography. The proposed PRBG is used to develop a new symmetr ic stream cipher for image encryption. Theoretic and numerical simulation analyses indicate that our image encryption algorithm is efficient and satisfies high security. Finally, we have proposed a new scheme which performs both lossless compression and encryption of image. The lossless compression is based on the binary AC (BAC) and the encryption is based on the proposed PRBG. The numerical simulation analysis indicates that the proposed compression and encryption scheme satisfies highly security with no loss of the BAC compression efficiency.

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The upcoming 5G mobile communications system promises to enable use cases requiring ultra-reliable and low latency communications. Researchers therefore require more detailed information about aspects such as channel coding performance at very low block error rates. The simulations needed to obtain such results are very time consuming and this poses achallenge to studying the problem. This thesis investigates the use of hardware acceleration for performing fast simulations of turbo code performance. Special interest is taken in investigating different methods for generating normally distributed noise based on pseudorandom number generator algorithms executed in DSP:s. A comparison is also done regarding how well different simulator program structures utilize the hardware. Results show that even a simple program for utilizing parallel DSP:s can achieve good usage of hardware accelerators and enable fast simulations. It is also shown that for the studied process the bottleneck is the conversion of hard bits to soft bits with addition of normally distributed noise. It is indicated that methods for noise generation which do not adhere to a true normal distribution can further speed up this process and yet yield simulation quality comparable to methods adhering to a true Gaussian distribution. Overall, it is show that the proposed use of hardware acceleration in combination with the DSP software simulator program can in a reasonable time frame generate results for turbo code performance at block error rates as low as 10−9.

Un dels majors problemes experimentats pels sistemes de detecció de gasos basats en sensors d'òxids metàl·lics és la seva manca de reproduibilitat, estabilitat i selectivitat. A fi i a efecte d'intentar resoldre aquest problemes, diferents estratègies han estat desenvolupades en paral·lel. Algunes es relacionen a la millora dels materials i d'altres impliquen el condicionament o el pre-tractament de les mostres. Les més emprades han consistit en aprofitar que els sensors presenten sensibilitats solapades per construir matrius de sensors i emprar tècniques de processament del senyal o bé utilitzar característiques de la resposta dinàmica dels sensors. En els darrers anys, modular la temperatura de treball del sensors d'òxids metàl·lics s'ha convertit en un dels mètodes més utilitzats per incrementar-ne la selectivitat. Això s'esdevé així donat que la resposta del sensor varia amb la seva temperatura de treball. Per això, en determinats casos, mesurant la resposta d'un sensor a n temperatures de treball diferents pot ser equivalent a tenir una matriu de n sensors diferents. Això permet obtenir informació multivariant de cada sensor individualment i ajuda a mantenir baixa la dimensionalitat del sistema de mesura per resoldre una determinada aplicació. Malgrat que molts i bons resultats han estat publicats dins aquest àmbit, la tria de les freqüències emprades en la modulació de la temperatura de treball dels sensor ha consistit fins ara en un procés empíric que no garanteix la obtenció dels millors resultats per una determinada aplicació. En aquest context, el principal objectiu d'aquesta tesi doctoral ha consistit en desenvolupar un mètode sistemàtic que permeti determinar quines són les freqüències de modulació òptimes que caldria emprar per resoldre un determinat problema d'anàlisi de gasos. Aquest mètode, extret del camp d'identificació de sistemes, ha esta desenvolupat i implementat per primer cop dins l'àmbit dels sensors de gasos. Aquest consisteix en estudiar la resposta dels sensors en presència de gasos mentre la temperatura de treball dels sensors és modulada per un senyal pseudo-aleatori de longitud màxima. Aquest senyals comparteixen algunes propietats amb el soroll blanc, i per tant poden ajudar a estimar la resposta lineal d'un sistema amb no-linealitats (per exemple, la resposta impulsional d'un sistema sensor-gas). El procés d'optimització es duu a terme mitjançant la selecció entre els components espectrals de les estimacions de la resposta impulsional, d'aquells que millor ajuden bé a discriminar o a quantificar els gasos objectiu dins una aplicació d'anàlisi de gasos donada. Tenint en compte que els components espectrals estan directament relacionats amb les xvii Improving the performance of micro-machined metal oxide gas sensors: Optimization of the temperature modulation mode via pseudo-random sequences. freqüències de modulació, la tria d'uns pocs components espectrals resulta en la determinació de les freqüències òptimes de modulació. En els primer experiments, senyals binaris pseudo-aleatoris van ser emprats per modular la temperatura de treball de sensors de gasos basats en òxids metàl·lics micro-mecanitzats dins d'un rang comprès entre 0 i 112,5 Hz. La freqüència superior és lleugerament superior a la frequència de tall de les membranes dels sensors. El resultat principal derivat d'aques estudi va ser que les freqüències de modulació interessants es trobaven en un rang comprès entre 0 i 1 Hz. Això és comprensible donat que la cinètica de les reaccions i dels processos d'adsorció que es produeixen en la superfície dels sensors són lentes i si aquestes s'han de veure modificades per la modulació térmica, llavors caldran senyals de modulació de baixa freqüència. Això explica perquè s'han vingut emprant senyals moduladores de temperatura en el rang dels mHz, malgrat que les membranes d'un dispositiu micromecanitzat presenten respostes tèrmiques molts més ràpides (típicament de l'ordre de 100 Hz). En els experiments que continuaren els primers, un mètode evolucionat per determinar les freqüències de modulació tèrmica òptimes va ser implementat. Aquest es basa en l'ús de seqüències pseudo-aleatòries multi-nivell de longitud màxima. Els senyals de tipus multi-nivell van ser considerats en substitució dels senyals binaris ja que els primers permeten obtenir una millor estimació que els segons de la dinàmica lineal d'un sistema amb no linealitats. I és ben conegut que els sensors de gasos basats en òxids metàl·lics presenten no linealitat en la seva resposta. Aquests estudis sistemàtics van ser completament validats mitjançant la síntesi de senyals multi-sinusoïdals amb les freqüències prèviament identificades emprant sequències pseudo-aleatòries. Quan la temperatura de treball dels sensors va ser modulada amb un senyal, el contingut freqüencial del qual era l'òptim, els gasos i les mescles de gasos considerades van poder ser discriminades perfectament i es va mostrar la possibilitat d'obtenir models de calibració acurats per predir la concentració dels gasos. En alguns casos, aquest procés de validació es va portar a terme emprant sensors que no havien estat utilitzats durant el procés d'optimització (per exemple, una agrupació de sensors diferent però del mateix lot de fabricació). En resum, el nou mètode desenvolupat en aquesta tesi per seleccionar les freqüències de modulació òptimes s'ha mostrat consistent i efectiu. El mètode és d'aplicació general i podria ser emprat en qualsevol problema d'anàlisi de gasos o bé estès a altres tipus de sensors (per exemple sensors polimèrics). Les contribucions científiques d'aquesta tesi s'han recollit en quatre articles en revistes internacionals i 13 llibres d'actes de conferències. / Uno de los mayores problemas experimentados en los sistemas de detección de gases basados en dispositivos de óxidos metálicos es su falta de reproducibilidad, estabilidad y selectividad. Con el fin de intentar resolver estos problemas, diferentes estrategias han sido desarrolladas en paralelo. Algunas de ellas se relacionan con la mejora de los materiales y otras implican acondicionamiento o pre-tratamiento de las muestras. Otras estrategias ampliamente empleadas consisten en aprovechar que los sensores presentan sensibilidades solapadas para construir matrices de sensores y emplear técnicas de procesamiento de señal o bien utilizar características de la respuesta dinámica de los sensores.En los últimos años, modular la temperatura de trabajo de los sensores de óxidos metálicos se ha convertido en uno de los métodos más utilizados para incrementar su selectividad. Esto se debe a, dado que la respuesta del sensor varía con su propia temperatura de trabajo, entonces, en determinados casos, midiendo la respuesta de un sensor a n temperaturas de trabajo diferentes, es equivalente a tener una matriz de n sensores diferentes. Esto permite obtener información multivariante de cada sensor individualmente y ayuda a mantener baja la dimensionalidad del sistema de medida para resolver una determinada aplicación. A pesar de los buenos resultados que han sido publicados dentro de este ámbito, la selección de las frecuencias empleadas en la modulación de la temperatura de trabajo de los sensores ha consistido, hasta el momento, en un proceso empírico lo que no garantiza la obtención de los mejores resultados para una determinada aplicación.En este contexto, el principal objetivo de esta tesis doctoral ha consistido en desarrollar un método sistemático que permita determinar cuales son las frecuencias de modulación óptimas que podrían emplearse para resolver un determinado problema de análisis de gases. Este método, extraído del campo de identificación de sistemas, ha sido desarrollado e implementado por primera vez dentro del ámbito de los sensores de gases. Éste consiste en estudiar la respuesta de los sensores en presencia de gases mientras la temperatura de trabajo de los sensores es modulada mediante una señal pseudo-aleatoria de longitud máxima. Estas señales comparten algunas propiedades con el ruido blanco, y por tanto pueden ayudar a estimar la respuesta lineal de un sistema con no-linealidades (por ejemplo, la respuesta impulsional de un sistema sensor-gas).El proceso de optimización es llevado a cabo mediante la selección entre las componentes espectrales de las estimaciones de la respuesta impulsional, de aquellas que más ayudan ya sea a discriminar o a cuantificar los gases objetivo dentro de una aplicación de análisis de gases dada. Teniendo en cuenta que las componentes espectrales están directamente relacionadas con las frecuencias de modulación, la selección de unas pocas componentes espectrales resulta en la determinación de las frecuencias optimas de modulación.En los primeres experimentos, señales binarias pseudo-aleatorias fueron utilizadas para modular la temperatura de trabajo de los sensores de gases basados en óxidos metálicos micro-mecanizados en un rango comprendido entre 0 a 112.5 Hz. La frecuencia superior es ligeramente mayor a la frecuencia de corte de las membranas de los sensores. El resultado principal derivado de estos estudios fue que las frecuencias de modulación interesantes se encuentran en un rango comprendido entre 0 y 1 Hz. Esto es comprensible dado que la cinética de las reacciones y de los procesos de adsorción que se producen en la superficie del sensor son lentos y si estos se han de alterar mediante la modulación térmica, se habrá de elaborar señales de modulación a bajas frecuencias. Esto explica por que se han venido empleado señales moduladoras de temperatura en el rango de los mHz, a pesar que las membranas de un dispositivo micro-mecanizado presentan respuestas mucho más rápidas (típicamente en el orden de los 100 Hz).En los experimentos posteriores a los primeros, un método evolucionado para determinar las frecuencias de modulación óptimas de los sensores micro-mecanizados fue implementado, el cual se basa en el uso de secuencias pseudo-aleatorias multi-nivel de longitud máxima (MLPRS). Las señales de tipo multi-nivel fueron consideradas en lugar de las binarias ya que las primeras permiten obtener una mejor estimación que las segundas de la dinámica lineal de un sistema con no linealidades. Y es bien conocido que los sensores de gases basados en óxidos metálicos presentan no-linealidades en su respuesta.Estos estudios sistemáticos fueron completamente validados mediante la síntesis de señales multi-senoidales con las frecuencias previamente identificadas utilizando secuencias pseudo-aleatorias. Cuando la temperatura de trabajo de los sensores fue modulada por una señal, el contenido frecuencial de la cual es el óptimo, los gases y mezclas de gases considerados pudieron ser discriminados perfectamente y se verificó la posibilidad de obtener modelos de calibración precisos para predecir la concentración de los gases. En algunos casos, estos procesos de validación se llevaron a cabo con sensores que no habían sido utilizados durante el proceso de optimización (por ejemplo, una agrupación de sensores diferentes pero del mismo lote de fabricación).En resumen, El nuevo método desarrollado in esta tesis para seleccionar las frecuencias de modulación optimas se a mostrado consistente y efectivo. El método es de aplicación general y podría ser utilizado en cualquier problema de análisis de gases o bien extendido a otro tipo de sensores (por ejemplo sensores poliméricos).Las contribuciones científicas de esta tesis se han recogido en 4 artículos en revistas internacionales y trece actas de conferencias. / One of the major problems in gas sensing systems that use metal oxide devices is the lack of reproducibility, stability and selectivity. In order to tackle these troubles experienced with metal oxide gas sensors, different strategies have been developed in parallel. Some of these are related to the improvement of materials, or the use of sample conditioning and pre-treating methods. Other widely used techniques include taking benefit of the unavoidable partially overlapping sensitivities by using sensor arrays and pattern recognition techniques or the use of dynamic features from the gas sensor response.In the last years, modulating the working temperature of metal oxide gas sensors has been one of the most used methods to enhance sensor selectivity. This occurs because, since, the sensor response is different at different working temperatures, and therefore, measuring the sensor response at n different temperatures is, in some cases, similar to the use of an array comprising n different sensors. This allows for measuring multivariate information from every single sensor and helps in keeping low the dimensionality of the measurement system needed to solve a specific application. Although the good results reported, until now, the selection of the frequencies used to modulate the working temperature remained an empirical process and that is not an accurate method to ensure that the best results are reached for a given application.In view of this context, the principal objective of this doctoral thesis was to develop a systematic method to determine which are the optimal temperature modulation frequencies to solve a given gas analysis problem. This method, which is borrowed from the field of system identification, has been developed and introduced for the first time in the area of gas sensors. It consists of studying the sensor response to gases when the operating temperature is modulated via maximum-length pseudo-random sequences. Such signals share some properties with white noise and, therefore, can be of help to estimate the linear response of a system with non-linearity (e.g., the impulse response of a sensor-gas system).The optimization process is conducted by selecting among the spectral components of the impulse response estimates, the few that better help either discriminating or quantifying the target gases of a given gas analysis application. Since spectral components are directly related to modulating frequencies, the selection of spectral components results in the determination of the optimal temperature modulating frequencies.In the first experiments, pseudo-random binary signals (PRBS) were employed to modulate the working temperature of micro-machined metal oxide gas sensors in a frequency range from 0 up to 112.5 Hz. The upper frequency is slightly higher than the cutoff frequency of the sensor membranes. The outcome of this initial study was that the important modulating frequencies were in the range between 0 and 1 Hz. This is understandable, since the kinetics of reaction and adsorption processes taking place at the sensor surface (i.e., physisorption/chemisorption/ionosorption) are slow and if these are to be altered by the thermal modulation, low frequency modulating signals need to be devised. This explains why low-frequency temperature-modulating signals (i.e. in the mHz range) have been used with micro-hotplate gas sensors, even though the thermal response of their membranes is much faster (typically, near 100 Hz).In the experiments that followed the first ones, an evolved method to determine the optimal temperature modulating frequencies for micro-hotplate gas sensors was introduced, which was based on the use of maximum length multilevel pseudo-random sequences (MLPRS). Multilevel signals were considered instead of the binary ones because the former can provide a better estimate than the latter of the linear dynamics of a process with non-linearity. And it is well known that temperature-modulated metal oxide gas sensors present non-linearity in their response.These systematic studies were fully validated by synthesizing multi-sinusoidal signals at the optimal frequencies previously identified using pseudo-random sequences. When the sensors had their operating temperatures modulated by a signal with a frequency content that corresponded to the optimal, the gases and gas mixtures considered could be perfectly discriminated and the building of accurate calibration models to predict gas concentration was found to be possible. In some cases, the validation process was conducted on sensors that had not been used for optimization purposes (e.g. a different sensor array from the same fabrication batch).Summarizing, the new method developed in this thesis for selecting the optimal modulating frequencies is shown to be consistent and effective. The method applies generally and could be used in any gas analysis problem or extended to other type of sensors (e.g. conducting polymer sensors).The scientific contributions of this thesis are collected in four journal papers and thirteen conference proceedings.

The need to characterise a PEM electrolyser is motivated by a South African hydrogen company. One of two electrochemical characterisation methods, namely the current interrupt method or electrochemical impedance spectroscopy, is investigated to characterise the PEM electrolyser. Various literature sources can be found on the electrochemical characterisation methods. In this study the current interrupt method is used for the electrochemical characterisation of a PEM electrolyser. The current interrupt method is an electrical test method that will be used to obtain an equivalent electric circuit model of the PEM electrolyser. The equivalent electric circuit model relates to various electrochemical characteristics such as the activation losses, the ohmic losses and the concentration losses. Two variants of the current interrupt method, namely the natural voltage response method and the current switching method, are presented. These methods are used to obtain two different equivalent electric circuit models of the PEM electrolyser. The parameters of the first equivalent electric circuit, namely the Randles cell, will be estimated with the natural voltage response method. The parameters of the second equivalent electric circuit, namely the Randles-Warburg cell, will be estimated with the current switching method. Simulation models of the equivalent electric circuits are developed and tested. The simulation models are used to verify and validate the natural voltage response method and the current switching method. The parameters of the Randles cell simulation model is accurately calculated with the natural voltage response method. The parameters of the Randles-Warburg cell simulation model is accurately calculated with the current switching method. The natural voltage response method and the current switching method are also practically implemented. The results is used to indicate the various electrochemical characteristics of the PEM electrolyser. A Nafion 117 type membrane was tested with the current interrupt method. The membrane resistance parameters of Randles cell were estimated with the natural voltage response method. These values are validated with conductivity measurements found in literature. The results of the Randles- Warburg cell is validated with a system identification validation model. / Thesis (MIng (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2013

The need to characterise a PEM electrolyser is motivated by a South African hydrogen company. One of two electrochemical characterisation methods, namely the current interrupt method or electrochemical impedance spectroscopy, is investigated to characterise the PEM electrolyser. Various literature sources can be found on the electrochemical characterisation methods. In this study the current interrupt method is used for the electrochemical characterisation of a PEM electrolyser. The current interrupt method is an electrical test method that will be used to obtain an equivalent electric circuit model of the PEM electrolyser. The equivalent electric circuit model relates to various electrochemical characteristics such as the activation losses, the ohmic losses and the concentration losses. Two variants of the current interrupt method, namely the natural voltage response method and the current switching method, are presented. These methods are used to obtain two different equivalent electric circuit models of the PEM electrolyser. The parameters of the first equivalent electric circuit, namely the Randles cell, will be estimated with the natural voltage response method. The parameters of the second equivalent electric circuit, namely the Randles-Warburg cell, will be estimated with the current switching method. Simulation models of the equivalent electric circuits are developed and tested. The simulation models are used to verify and validate the natural voltage response method and the current switching method. The parameters of the Randles cell simulation model is accurately calculated with the natural voltage response method. The parameters of the Randles-Warburg cell simulation model is accurately calculated with the current switching method. The natural voltage response method and the current switching method are also practically implemented. The results is used to indicate the various electrochemical characteristics of the PEM electrolyser. A Nafion 117 type membrane was tested with the current interrupt method. The membrane resistance parameters of Randles cell were estimated with the natural voltage response method. These values are validated with conductivity measurements found in literature. The results of the Randles- Warburg cell is validated with a system identification validation model. / Thesis (MIng (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2013

This work presents a black box identification for a continuous methanol-water distillation column setting in open loop and closed loop response. Step changes and Pseudo-Random Binary Signal (PRBS) disturbance were used to excite the plant. The mathematical models candidates to identify were the Artificial Neural Networks (ANN) and the parametric models: ARX(autoregressive with exogenous inputs ), ARMAX (AutoRegressive Moving Average with eXogenous inputs ), OE(Output Error) and the Box-Jenkins (BJ)structure. The closed loop configuration was the R-V. The results showed that for the bottom loop, the best response were given by BJ, OE and RNA for both open and closed loop response. For the top closed loop, the best responses were also given by BJ, OE and RNA while in open loop condition, the RNA was the one that gave satisfactory outcome. It was verified that the pseudo-random binary signal was a good choice of excitation signal in identification for both open loop and closed dynamic systems. / Foi realizado neste trabalho identificação caixa preta do processo de destilação Metanol-Água nas configurações malha aberta e malha fechada, utilizando como sinais de perturbação a função degrau e o Sinal Binário Pseudo-Aleatório (PRBS) para excitar a planta. Os modelos matemáticos candidatos a identificação foram as Redes Neurais Artificiais (RNA), e os modelos paramétricos discretos lineares autorregressivo com entradas externas (ARX do inglês AutoRegressive with eXogenous Inputs), autorregressivo com média móvel e entradas exógenas (ARMAX do inglês AutoRegressive Moving Average with eXogenous Inputs), modelo do tipo erro na saída (OE do inglês Output Error) e a estrutura Box-Jenkins (BJ). Com a disposição dos modelos, foram comparados quais dos modelos matemáticos candidatos à identificação melhor representa o processo coluna de destilação metanol-água. Comparou-se qual configuração do processo no ensaio de identificação para geração de dados apresenta mais vantagens, se em malha aberta ou em malha fechada, nas condições e metodologias utilizadas. Constatou-se a funcionalidade do sinal binário pseudo-aleatório como uma boa opção de excitação na identificação em malha aberta e fechada para sistemas dinâmicos.

Nowadays, network security plays a major role in the field of wireless communications. Wired networks propagate electrical signals or pulses through cables. Whereas wireless signals propagate through the air. If wireless networks are left open and exposed to the outside world, there are high chances of being misused by others. The intruders take advantage of this, to intercept the wireless signals. This is the reason why an extra level of security is required for wireless networks. The physical layer is one of the important layers of the Open System Interconnection (OSI) model which plays an important role in the network’s physical connections like wireless transmission, cabling, connections etc. The physical layer supports the bit-level transmission between various devices by connecting to the physical medium for synchronized communication.In this thesis, a method is studied for exchanging secret key [1] bits using a pseudo-random sequence generator based on Frequency Division Duplex (FDD) systems. The principle of this method is to generate a secret key in a manner that produces low correlation at the intruder. By uniquely relating the secret key bits to the channel in a private version of the universal codebook, a robust key exchange between the transmitter and the receiver is then performed.

Development of computer networks able to operate at the speed of 10 Gb/s imposes new requirements on newly developed network devices and also on a process of their testing. Such devices are tested by replaying synthetic or previously captured network traffic on an input link of the tested device. We must be able to perform both tasks also at full wire speed. Current testing devices are either not able to operate at the speed of 10 Gb/s or they are too expensive. Therefore, the aim of this thesis is to design and implement a hardware accelerated application able to generate and replay network traffic at the speed of 10 Gb/s. The application is accelerated in the FPGA of the COMBOv2 card and it also utilizes the NetCOPE platform. Architecture of the application is modular, which allows easy implementation of different modes of operation. The application implements both capturing and replaying network traffic at full wire speed, but traffic can be limited to a specified value of bitrate at the output. The thesis is concluded by a comparison of the implemented application and the packet generator implemented on the NetFPGA platform. According to this comparison, the implemented application is better than the NetFPGA packet generator.