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In cloud computing, computation is demanded to several cloud computing servers and each of them can have access to different data sets. Such data and also the derived computation results could not be publicly shared among the clou...
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In cloud computing, computation is demanded to several cloud computing servers and each of them can have access to different data sets. Such data and also the derived computation results could not be publicly shared among the clouds involved for privacy reasons. Secure Multi-Party Computation (SMPC) protocols could be used to protect private data during computation. The search for efficient universal computing architectures is an active research topic in SMPC. By extending a previous protocol for the piece-wise linear approximation of a generic one-dimensional function, a new SMPC protocol for the approximation of n-dimensional functions f(x1,???, xn) can be developed. In the case of two inputs, a quad-tree decomposition is used to decompose the function domain into subsets wherein a constant or a bilinear approximation is used. This solution can be easily extended to the approximation of n-variate functions. Two different implementations are considered: the first one relies completely on Garbled Circuits (GC), while the second one exploits a hybrid construction where GC and Homomorphic Encryption (HE) are used together. As it is shown in the present paper, the best choice between the two approaches depends on the specific settings with the hybrid solution being preferable for inputs characterized by a large bit-length.
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摘要 :
In cloud computing, computation is demanded to several cloud computing servers and each of them can have access to different data sets. Such data and also the derived computation results could not be publicly shared among the clou...
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In cloud computing, computation is demanded to several cloud computing servers and each of them can have access to different data sets. Such data and also the derived computation results could not be publicly shared among the clouds involved for privacy reasons. Secure Multi-Party Computation (SMPC) protocols could be used to protect private data during computation. The search for efficient universal computing architectures is an active research topic in SMPC. By extending a previous protocol for the piece-wise linear approximation of a generic one-dimensional function, a new SMPC protocol for the approximation of n-dimensional functions f(x1,???, xn) can be developed. In the case of two inputs, a quad-tree decomposition is used to decompose the function domain into subsets wherein a constant or a bilinear approximation is used. This solution can be easily extended to the approximation of n-variate functions. Two different implementations are considered: the first one relies completely on Garbled Circuits (GC), while the second one exploits a hybrid construction where GC and Homomorphic Encryption (HE) are used together. As it is shown in the present paper, the best choice between the two approaches depends on the specific settings with the hybrid solution being preferable for inputs characterized by a large bit-length.
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The authors present an approach for the approximate input-output linearization of nonlinear systems, particularly those for which relative degree is not well defined. They show that there is a great deal of freedom in the selectio...
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The authors present an approach for the approximate input-output linearization of nonlinear systems, particularly those for which relative degree is not well defined. They show that there is a great deal of freedom in the selection of an approximation and that, by designing a tracking controller based on the approximating system, tracking of reasonable trajectories can be achieved with small error. The approximating system is itself a nonlinear system, with the difference that it is input-output linearizable by state feedback. The authors demonstrate some properties of the accuracy of the approximation and, in the context of the ball and beam example, show it to be far superior to the Jacobian approximation. The results are focused on finding regular SISO systems which are close to systems which are not regular and controlling these approximate regular systems.
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A common problem in optical motion capture of human-body movement is the so-called missing marker problem. The occlusion of markers can lead to significant problems in tracking accuracy unless a continuous flow of data is guarante...
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A common problem in optical motion capture of human-body movement is the so-called missing marker problem. The occlusion of markers can lead to significant problems in tracking accuracy unless a continuous flow of data is guaranteed by interpolation or extrapolation algorithms. Since interpolation algorithms require data sampled before and after an occlusion, they cannot be used for real-time applications. Extrapolation algorithms only require data sampled before an occlusion. Other algorithms require statistical data and are designed for postprocessing. In order to bridge sampling gaps caused by occluded markers and hence to improve 3D real-time motion capture, we suggest a computationally cost-efficient extrapolation algorithm partly combined with a so-called constraint matrix. The realization of this prediction algorithm does not require statistical data nor does it rely on an underlying kinematic human model with pre-defined marker distances. Under the assumption that human motion can be linear, circular, or a linear combination of both, a prediction method is realized. The paper presents measurements of a circular movement wherein a marker is briefly lost. The suggested extrapolation method behaves well for a reasonable number of frames, not exceeding around two seconds of time.
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摘要 :
A common problem in optical motion capture of human-body movement is the so-called missing marker problem. The occlusion of markers can lead to significant problems in tracking accuracy unless a continuous flow of data is guarante...
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A common problem in optical motion capture of human-body movement is the so-called missing marker problem. The occlusion of markers can lead to significant problems in tracking accuracy unless a continuous flow of data is guaranteed by interpolation or extrapolation algorithms. Since interpolation algorithms require data sampled before and after an occlusion, they cannot be used for real-time applications. Extrapolation algorithms only require data sampled before an occlusion. Other algorithms require statistical data and are designed for postprocessing. In order to bridge sampling gaps caused by occluded markers and hence to improve 3D real-time motion capture, we suggest a computationally cost-efficient extrapolation algorithm partly combined with a so-called constraint matrix. The realization of this prediction algorithm does not require statistical data nor does it rely on an underlying kinematic human model with pre-defined marker distances. Under the assumption that human motion can be linear, circular, or a linear combination of both, a prediction method is realized. The paper presents measurements of a circular movement wherein a marker is briefly lost. The suggested extrapolation method behaves well for a reasonable number of frames, not exceeding around two seconds of time.
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In this paper we explore the recovery of key information from a block cipher when using unbiased linear approximations of a certain form. In particular we develop a theoretical framework for their treatment and we confirm their be...
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In this paper we explore the recovery of key information from a block cipher when using unbiased linear approximations of a certain form. In particular we develop a theoretical framework for their treatment and we confirm their behaviour with experiments on reduced-round variants of DES. As an application we show a novel form of linear cryptanalysis using multiple linear approximations which can be used to extract key information when all pre-existing techniques would fail.
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In this paper we explore the recovery of key information from a block cipher when using unbiased linear approximations of a certain form. In particular we develop a theoretical framework for their treatment and we confirm their be...
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In this paper we explore the recovery of key information from a block cipher when using unbiased linear approximations of a certain form. In particular we develop a theoretical framework for their treatment and we confirm their behaviour with experiments on reduced-round variants of DES. As an application we show a novel form of linear cryptanalysis using multiple linear approximations which can be used to extract key information when all pre-existing techniques would fail.
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Phylogenetic tree reconstruction is a fundamental biological problem Quartet amalgamation combining a set of trees over four taxa into a tree over the full set stands at the heart of many phylogenetic reconstruction methods. Howev...
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Phylogenetic tree reconstruction is a fundamental biological problem Quartet amalgamation combining a set of trees over four taxa into a tree over the full set stands at the heart of many phylogenetic reconstruction methods. However, even reconstruction from a consistent set of quartet trees, i.e. all quartets agree with some tree, is NP- hard, and the best approximation ratio known is 1/3. For a dense input of 0(n~4) quartets (not necessarily consistent), the problem has a polynomial time approximation scheme. When the number of taxa grows, considering such dense inputs is impractical and some sampling approach is imperative. In this paper we show that if the number of quartets sampled is at least Θ(n~2 log n), there is a randomized approximation scheme, that runs in linear time in the number of quartets The previously known polynomial approximation scheme for that problem required a very dense sample of size Θ(n~4). We note that samples of size Θ(n~2 log n) are sparse in the full quartet set.
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Linear blending is a very popular skinning technique for virtual characters, even though it does not always generate realistic deformations. Recently, nonlinear blending techniques (such as dual quaternions) have been proposed in ...
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Linear blending is a very popular skinning technique for virtual characters, even though it does not always generate realistic deformations. Recently, nonlinear blending techniques (such as dual quaternions) have been proposed in order to improve upon the deformation quality of linear skinning. The trade-off consists of the increased vertex deformation time and the necessity to redesign parts of the 3D engine. In this paper, we demonstrate that any nonlinear skinning technique can be approximated to an arbitrary degree of accuracy by linear skinning, using just a few samples of the nonlinear blending function (virtual bones). We propose an algorithm to compute this linear approximation in an automatic fashion, requiring little or no interaction with the user. This enables us to retain linear skinning at the core of our 3D engine without compromising the visual quality or character setup costs.
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摘要 :
Linear blending is a very popular skinning technique for virtual characters, even though it does not always generate realistic deformations. Recently, nonlinear blending techniques (such as dual quaternions) have been proposed in ...
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Linear blending is a very popular skinning technique for virtual characters, even though it does not always generate realistic deformations. Recently, nonlinear blending techniques (such as dual quaternions) have been proposed in order to improve upon the deformation quality of linear skinning. The trade-off consists of the increased vertex deformation time and the necessity to redesign parts of the 3D engine. In this paper, we demonstrate that any nonlinear skinning technique can be approximated to an arbitrary degree of accuracy by linear skinning, using just a few samples of the nonlinear blending function (virtual bones). We propose an algorithm to compute this linear approximation in an automatic fashion, requiring little or no interaction with the user. This enables us to retain linear skinning at the core of our 3D engine without compromising the visual quality or character setup costs.
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