Thèses sur le sujet « Transformée de Walsh »
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Flórez, Gutiérrez Antonio. « Improved Techniques in the Cryptanalysis of Symmetric Primitives ». Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS281.
Texte intégralThis thesis proposes improvements which can be applied to several techniques for the cryptanalysis of symmetric primitives. Special attention is given to linear cryptanalysis, for which a technique based on the fast Walsh transform was already known (Collard et al., ICISIC 2007). We introduce a generalised version of this attack, which allows us to apply it on key recovery attacks over multiple rounds, as well as to reduce the complexity of the problem using information extracted, for example, from the key schedule. We also propose a general technique for speeding key recovery attacks up which is based on the representation of Sboxes as binary decision trees. Finally, we showcase the construction of a linear approximation of the full version of the Gimli permutation using mixed-integer linear programming (MILP) optimisation
Lazaridis, George. « Image processing using the Walsh transform ». Thesis, University of Surrey, 2004. http://epubs.surrey.ac.uk/843950/.
Texte intégralFuris, Mihai Alexandru Johnson Jeremy. « Cache miss analysis of Walsh-Hadamard Transform algorithms / ». Philadelphia : Drexel University, 2003. http://dspace.library.drexel.edu/handle/1721.1/109.
Texte intégralO'Dowd, Timothy R. « Discovery of bent functions using the Fast Walsh Transform ». Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5080.
Texte intégralLinear cryptanalysis attacks are a threat against cryptosystems. These attacks can be defended against by using combiner functions composed of highly nonlinear Boolean functions. Bent functions, which have the highest possible nonlinearity, are uncommon. As the number of variables in a Boolean function increases, bent functions become extremely rare. A method of computing the nonlinearity of Boolean functions using the Fast Walsh Transform (FWT) is presented. The SRC-6 reconfigurable computer allows testing of functions at a much faster rate than a PC. With a clock frequency of 100 MHz, throughput of the SRC-6 is 100,000,000 functions per second. An implementation of the FWT used to compute the nonlinearity of Boolean functions with up to five variables is presented. Since there are 22n Boolean functions of n variables, computation of the nonlinearity of every Boolean function with six or more variables takes thousands of years to complete. This makes discovery of bent functions difficult for large n. An algorithm is presented that uses information in the FWT of a function to produce similar functions with increasingly higher nonlinearity. This algorithm demonstrated the ability to enumerate every bent function for n = 4 without the necessity of exhaustively testing all fourvariable functions.
Davis, Jeffrey H. « A study of potential uses for Walsh transformed images in target recognition ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA292722.
Texte intégralDesmond, Allan Peter. « An analytical signal transform derived from the Walsh Transform for efficient detection of dual tone multiple frequency (DTMF) signals ». Thesis, Bucks New University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401474.
Texte intégralSagdicoglu, Serhat. « Cryptological Viewpoint Of Boolean Functions ». Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1082403/index.pdf.
Texte intégralRAJYALAKSHMI, P. S., et R. K. RAJANGAM. « DATA COMPRESSION SYSTEM FOR VIDEO IMAGES ». International Foundation for Telemetering, 1986. http://hdl.handle.net/10150/615539.
Texte intégralIn most transmission channels, bandwidth is at a premium and an important attribute of any good digital signalling scheme is to optimally utilise the bandwidth for transmitting the information. The Data Compression System in this way plays a significant role in the transmission of picture data from any Remote Sensing Satellite by exploiting the statistical properties of the imagery. The data rate required for transmission to ground can be reduced by using suitable compression technique. A data compression algorithm has been developed for processing the images of Indian Remote Sensing Satellite. Sample LANDSAT imagery and also a reference photo are used for evaluating the performance of the system. The reconstructed images are obtained after compression for 1.5 bits per pixel and 2 bits per pixel as against the original of 7 bits per pixel. The technique used is uni-dimensional Hadamard Transform Technique. The Histograms are computed for various pictures which are used as samples. This paper describes the development of such a hardware and software system and also indicates how hardware can be adopted for a two dimensional Hadamard Transform Technique.
Ahmed, Kamal Ali. « Digital watermarking of still images ». Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/digital-watermarking-of-still-images(0dc4b146-3d97-458f-9506-8c67bc3a155b).html.
Texte intégralEl, Omer. « Avalanche Properties And Randomness Of The Twofish Cipher ». Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605571/index.pdf.
Texte intégrals results. The strength of the cipher to cryptanalytic attacks is investigated by measuring its randomness according to the avalanche criterion. The avalanche criterion results are compared with those of the Statistical Test Suite of the NIST and discrepancies in the second and third rounds are explained theoretically.
Aydin, Ozge Zelal. « Detection Of Bladder Tumor Recurrence By Fourier Transform Infrared Spectroscopy As A Novel Method ». Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610883/index.pdf.
Texte intégralSertkaya, Isa. « Nonlinearity Preserving Post-transformations ». Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605183/index.pdf.
Texte intégrals results are obtained in terms of the post-transformations. In addition, the existence of nonlinearity preserving post-transformations, which are not equivalent to pre-transformations, is proved. The necessary and sufficient conditions for an affine post-transformation to preserve nonlinearity are proposed and proved. Moreover, the sufficient conditions for an non-affine post-transformation to keep nonlinearity invariant are proposed. Furthermore, it is proved that the smart hill climbing method, which is introduced to improve nonlinearity of Boolean functions by Millan et. al., is equivalent to applying a post-transformation to a single Boolean function. Finally, the necessary and sufficient condition for an affine pre-transformation to preserve the strict avalanche criterion is proposed and proved.
Millan, William L. « Analysis and design of Boolean functions for cryptographic applications ». Thesis, Queensland University of Technology, 1997.
Trouver le texte intégralZHENG, XIN-GU, et 鄭信富. « An application of walsh transform in PVC diagnoisis ». Thesis, 1986. http://ndltd.ncl.edu.tw/handle/50353655943156501853.
Texte intégralSharma, Purnima. « A microprocesser-based scheme using fast Walsh-Hadamard transform ». Thesis, 1986. http://localhost:8080/xmlui/handle/12345678/5409.
Texte intégralAnderson, Neil Arnold. « The classification of Boolean functions using the Rademacher-Walsh transform ». Thesis, 2007. http://hdl.handle.net/1828/221.
Texte intégralWen, Chia-Chang, et 溫家昶. « Researches on Generalized Legendre Sequence and Generalized Walsh-Fourier Transform ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/58183559898661696070.
Texte intégral國立臺灣大學
電信工程學研究所
102
The thesis contains two research topics: The first one is the discussion about the properties and applications of the complete generalized Legendre sequence (CGLS) and the second one is about the generalization between the Walsh-Hadamard transform (WHT) and the DFT and their properties. The CGLS is first defined to solve the DFT eigenvector problem. The proposed CGLS based DFT eigenvectors have the advantages of closed-form solutions, completeness, orthogonality, being well defined for arbitrary N, and fast DFT expansion so that the CGLS is helpful for developing DFT fast algorithms. Based on the CGLS researches, we can extend our results to the finite field operation. That means we can also use the CGLS over finite field (CGLSF) to solve the number theoretic transform (NTT) eigenvector problem. Mean while, we can apply the CGLS and CGLSF to constructing fast DFT(NTT) algorithm, fractional number theoretic transform (FNTT) definition and the switchable perfect shuffle transform (PST) system. The WHT and the DFT are two of the most important transforms for signal processing applications. Our purpose is to generalize these two transform by a single parameter so that the generalized transforms can not only have the advantages of the WHT and DFT but also have flexibility to some applications. We will first define the discrete orthogonal transform (DOT), conjugate symmetric discrete orthogonal transform (CS-DOT) and the fast finite field orthogonal transform (FFFOT). From the above transform, we can furthermore define the sequency ordered generalized Walsh-Fourier transform (SGWFT) and conjugate symmetric sequency ordered generalized Walsh-Fourier transform (CS-SGWFT) and show their properties and applications in CDMA sequence design, spectrum estimation and transform coding.
MacDonald, Roderick H. « A Walsh Transform ASIC design with built-in test using VHDL ». 1992. http://hdl.handle.net/1993/18588.
Texte intégralLin, Chun-Fan, et 林純帆. « Study of Orthogonal STBC Using Walsh-Hadamard Transform with Decoupling in Time Domain ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/01353163889531838536.
Texte intégral國立東華大學
電機工程學系
101
This thesis presents the Space-Time Block Codes (STBC) constructed by using the diagonal orthogonal coefficient with decoupling in time domain. The novel Walsh-Hadamard STBC (WHSTBC) gives full rate and full diversity order with appropriate pre-coding of the PSK or QAM modulated symbols, when the number of receiver antennas is at least equal to the number of transmit antennas. Hadamard matrices exist for orders equal to N=2^n, where n≥1, and the receiver allows for some decoupling methods and decoding with Maximal Ratio Combining (MRC). Finally, the performance will be different because of the different antennas and time arrangement.
Ting, Kou-Cheng, et 丁國政. « Designing Fast Walsh Hadamard Transform on Various Interconnection Networks Using Tensor Product Formulation ». Thesis, 2003. http://ndltd.ncl.edu.tw/handle/r8f2ma.
Texte intégral逢甲大學
資訊工程所
91
The fast Walsh Hadamard transform is a simple and important algorithm in digital signal processing, especially, in digital image compression. The fast Walsh Hadamard transform is a block recursive algorithm, which can be easily expressed as a tensor product formula. Also, the tensor product notation can be used to express the topology of interconnection networks. In this thesis, we will emerge the specification of tensor product formulation of block recursive algorithms and interconnection networks to design fast Walsh Hadamard transform algorithms on various interconnection networks, including hypercube networks, omega networks, and baseline networks. The design process starts from a tensor product formula of the fast Walsh Hadamard transform. Given a specific interconnection network, we will manipulate the tensor product formula of the fast Walsh Hadamard transform to an equivalent formula which fits the form of the tensor product formula of that interconnection network. The resulting algorithms are suitable for designing VLSI circuits of DSP algorithms.
Tsai, Yao-Tsung, et 蔡曜聰. « Identification and Redution fo 2-D Discrete-time LSI Systmn via Discrete Walsh Transform ». Thesis, 1990. http://ndltd.ncl.edu.tw/handle/23957526741177142652.
Texte intégral國立交通大學
控制工程研究所
78
The discrete Walsh transform (DWT) is applied to response analysis, identification and model reduction of the 2-D discrete-time LSI system. The data arrays are transformed into discrete Walsh spectrum matrices using DWT. First, with the shift DWT being utilized and the Walsh spectra manipulated by Kronecker product of two matrices, the response of 2-D system can be easily evaluated for arbitrary in- put with zero initial conditions. Next, from the point of view of data matching, the transfer function of 2-D system is identified from finite input-output data, where the output is mixed with uniformly distributed disturbance. In the third part, the 2-D discrete Walsh spectrum matching approach is also used for reducing the transfer function of a given 2-D system to a lower order model. Examples are illustrated to demonstrate the usefulness. Moreover, an electronic circuit, based on a neural net, to compute the DWT is also presented. The circuit behavior is analyzed and the fabrication problem is considered as well. Simulation results show that the proposed circuit is suitable for real-time DWT computation.
Chen, Kuan-Han, et 陳冠翰. « SELECTIVE MAPPING SCHEME COMBINING WITH WALSH HADAMARD TRANSFORM FOR PAPR REDUCTION OF OFDM SYSTEMS ». Thesis, 2009. http://ndltd.ncl.edu.tw/handle/58893504047388376254.
Texte intégral大同大學
通訊工程研究所
97
Orthogonal Frequency Division Multiplex (OFDM) is a very suitable technique for achieving high-rate wireless data transmission. High spectral efficiency, robustness to channel fading, immunity to impulse interference and less non linear distortion are among the favorite properties of OFDM. One major drawback of OFDM is high Peak to Average Power Ratio (PAPR) of the transmitted signal. The high peaks of an OFDM signal are distorted nonlinearly by the high power amplifier (HPA) because the HPA heavily distorts all signal parts that come close to or exceed saturation. The distortion causes inter carrier interference (ICI) and out-of-band (OOB) radiation. While ICI disturbs the transmitted signal, it degrades the bit error rate (BER). OOB radiation disturbs signals on adjacent frequency bands, so it should be avoided. Several methods have been proposed in the literature to reduce the peak power of OFDM signals and substantial gains were reported. SLM (selective mapping) method is one of the efficient methods to reduce PAPR in OFDM system. However, SLM method has a serious disadvantage high calculation complexity. In this thesis, the proposed method using modified SLM scheme with WHT (Walsh Hadamard transform) to lower the high PAPR of OFDM system and lower the calculation complexity effectively
Chen, Chien-Hung, et 陳建宏. « The Joint Use of the Walsh-Hadamard Transform and Signal Companding Techniques for PAPR Reduction in OFDM Systems ». Thesis, 2004. http://ndltd.ncl.edu.tw/handle/59838485929160687499.
Texte intégral國立高雄第一科技大學
電腦與通訊工程所
92
The orthogonal frequency division multiplexing (OFDM) technique is one of the most attractive multicarrier modulation schemes for its high bandwidth efficiency and strong immunity to multipath fading. Even though there are many advantages of OFDM, it has two main drawbacks: high Peak to Average Power Ratio (PAPR) and frequency offset. To overcome these PAPR probblems, different methods have been proposed to mitigate the PAPR problem of OFDM. These techniques can be divided into two categories: Signal scrambling and Signal distortion technique. In the thesis, we study the PAPR reduction of OFDM transmission system by jointly using both Walsh-Hadamard transform and companding technique. First, Hadamard transform is used to decompose the correlation relationship of OFDM input sequence. On the other hand, since OFDM signal is similar to speech signals in the sense that large signals occur very infrequently, the companding technique usually applying to these signals might be used to improve OFDM transmission performance. Finally, we verify our analytical results by using Monte Carlo simulation.
Kadrolkar, Abhijit. « Energy Aware Signal Processing and Transmission for System Condition Monitoring ». 2010. https://scholarworks.umass.edu/theses/457.
Texte intégral