The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Erik Zenner - One of the best experts on this subject based on the ideXlab platform.
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a cryptanalysis of printcipher the Invariant Subspace attack
International Cryptology Conference, 2011Co-Authors: Gregor Leander, Mohamed Ahmed Abdelraheem, Hoda Alkhzaimi, Erik ZennerAbstract:At CHES 2010, the new block cipher PRINTcipher was presented as a light-weight encryption solution for printable circuits [15]. The best attack to date is a differential attack [1] that breaks less than half of the rounds. In this paper, we will present a new attack called Invariant Subspace attack that breaks the full cipher for a significant fraction of its keys. This attack can be seen as a weak-key variant of a statistical saturation attack. For such weak keys, a chosen plaintext distinguishing attack can be mounted in unit time. In addition to breaking PRINTcipher, the new attack also gives us new insights into other, more well-established attacks. We derive a truncated differential characteristic with a round-independent but highly key-dependent probability. In addition, we also show that for weak keys, strongly biased linear approximations exists for any number of rounds. In this sense, PRINTcipher behaves very differently to what is usually - often implicitly - assumed.
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CRYPTO - A cryptanalysis of PRINTcipher: the Invariant Subspace attack
Advances in Cryptology – CRYPTO 2011, 2011Co-Authors: Gregor Leander, Mohamed Ahmed Abdelraheem, Hoda Alkhzaimi, Erik ZennerAbstract:At CHES 2010, the new block cipher PRINTcipher was presented as a light-weight encryption solution for printable circuits [15]. The best attack to date is a differential attack [1] that breaks less than half of the rounds. In this paper, we will present a new attack called Invariant Subspace attack that breaks the full cipher for a significant fraction of its keys. This attack can be seen as a weak-key variant of a statistical saturation attack. For such weak keys, a chosen plaintext distinguishing attack can be mounted in unit time. In addition to breaking PRINTcipher, the new attack also gives us new insights into other, more well-established attacks. We derive a truncated differential characteristic with a round-independent but highly key-dependent probability. In addition, we also show that for weak keys, strongly biased linear approximations exists for any number of rounds. In this sense, PRINTcipher behaves very differently to what is usually - often implicitly - assumed.
Roger Ghanem - One of the best experts on this subject based on the ideXlab platform.
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an Invariant Subspace based approach to the random eigenvalue problem of systems with clustered spectrum
International Journal for Numerical Methods in Engineering, 2012Co-Authors: Debraj Ghosh, Roger GhanemAbstract:The repeated or closely spaced eigenvalues and corresponding eigenvectors of a matrix are usually very sensitive to a perturbation of the matrix, which makes capturing the behavior of these eigenpairs very difficult. Similar difficulty is encountered in solving the random eigenvalue problem when a matrix with random elements has a set of clustered eigenvalues in its mean. In addition, the methods to solve the random eigenvalue problem often differ in characterizing the problem, which leads to different interpretations of the solution. Thus, the solutions obtained from different methods become mathematically incomparable. These two issues, the difficulty of solving and the non-unique characterization, are addressed here. A different approach is used where instead of tracking a few individual eigenpairs, the corresponding Invariant Subspace is tracked. The spectral stochastic finite element method is used for analysis, where the polynomial chaos expansion is used to represent the random eigenvalues and eigenvectors. However, the main concept of tracking the Invariant Subspace remains mostly independent of any such representation. The approach is successfully implemented in response prediction of a system with repeated natural frequencies. It is found that tracking only an Invariant Subspace could be sufficient to build a modal-based reduced-order model of the system. Copyright (C) 2012 John Wiley & Sons, Ltd.
Gregor Leander - One of the best experts on this subject based on the ideXlab platform.
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a generic approach to Invariant Subspace attacks cryptanalysis of robin iscream and zorro
IACR Cryptology ePrint Archive, 2015Co-Authors: Gregor Leander, Brice Minaud, Sondre RonjomAbstract:Invariant Subspace attacks were introduced at CRYPTO 2011 to cryptanalyze PRINTcipher. The Invariant Subspaces for PRINTcipher were discovered in an ad hoc fashion, leaving a generic technique to discover Invariant Subspaces in other ciphers as an open problem. Here, based on a rather simple observation, we introduce a generic algorithm to detect Invariant Subspaces. We apply this algorithm to the CAESAR candidate iSCREAM, the closely related LS-design Robin, as well as the lightweight cipher Zorro. For all three candidates Invariant Subspaces were detected, and result in practical breaks of the ciphers. A closer analysis of independent interest reveals that these Invariant Subspaces are underpinned by a new type of self-similarity property. For all ciphers, our strongest attack shows the existence of a weak key set of density 2 32 . These weak keys lead to a simple property on the plaintexts going through the whole encryption process with probability one. All our attacks have been practically veried on reference implementations of the ciphers.
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a cryptanalysis of printcipher the Invariant Subspace attack
International Cryptology Conference, 2011Co-Authors: Gregor Leander, Mohamed Ahmed Abdelraheem, Hoda Alkhzaimi, Erik ZennerAbstract:At CHES 2010, the new block cipher PRINTcipher was presented as a light-weight encryption solution for printable circuits [15]. The best attack to date is a differential attack [1] that breaks less than half of the rounds. In this paper, we will present a new attack called Invariant Subspace attack that breaks the full cipher for a significant fraction of its keys. This attack can be seen as a weak-key variant of a statistical saturation attack. For such weak keys, a chosen plaintext distinguishing attack can be mounted in unit time. In addition to breaking PRINTcipher, the new attack also gives us new insights into other, more well-established attacks. We derive a truncated differential characteristic with a round-independent but highly key-dependent probability. In addition, we also show that for weak keys, strongly biased linear approximations exists for any number of rounds. In this sense, PRINTcipher behaves very differently to what is usually - often implicitly - assumed.
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CRYPTO - A cryptanalysis of PRINTcipher: the Invariant Subspace attack
Advances in Cryptology – CRYPTO 2011, 2011Co-Authors: Gregor Leander, Mohamed Ahmed Abdelraheem, Hoda Alkhzaimi, Erik ZennerAbstract:At CHES 2010, the new block cipher PRINTcipher was presented as a light-weight encryption solution for printable circuits [15]. The best attack to date is a differential attack [1] that breaks less than half of the rounds. In this paper, we will present a new attack called Invariant Subspace attack that breaks the full cipher for a significant fraction of its keys. This attack can be seen as a weak-key variant of a statistical saturation attack. For such weak keys, a chosen plaintext distinguishing attack can be mounted in unit time. In addition to breaking PRINTcipher, the new attack also gives us new insights into other, more well-established attacks. We derive a truncated differential characteristic with a round-independent but highly key-dependent probability. In addition, we also show that for weak keys, strongly biased linear approximations exists for any number of rounds. In this sense, PRINTcipher behaves very differently to what is usually - often implicitly - assumed.
Debraj Ghosh - One of the best experts on this subject based on the ideXlab platform.
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an Invariant Subspace based approach to the random eigenvalue problem of systems with clustered spectrum
International Journal for Numerical Methods in Engineering, 2012Co-Authors: Debraj Ghosh, Roger GhanemAbstract:The repeated or closely spaced eigenvalues and corresponding eigenvectors of a matrix are usually very sensitive to a perturbation of the matrix, which makes capturing the behavior of these eigenpairs very difficult. Similar difficulty is encountered in solving the random eigenvalue problem when a matrix with random elements has a set of clustered eigenvalues in its mean. In addition, the methods to solve the random eigenvalue problem often differ in characterizing the problem, which leads to different interpretations of the solution. Thus, the solutions obtained from different methods become mathematically incomparable. These two issues, the difficulty of solving and the non-unique characterization, are addressed here. A different approach is used where instead of tracking a few individual eigenpairs, the corresponding Invariant Subspace is tracked. The spectral stochastic finite element method is used for analysis, where the polynomial chaos expansion is used to represent the random eigenvalues and eigenvectors. However, the main concept of tracking the Invariant Subspace remains mostly independent of any such representation. The approach is successfully implemented in response prediction of a system with repeated natural frequencies. It is found that tracking only an Invariant Subspace could be sufficient to build a modal-based reduced-order model of the system. Copyright (C) 2012 John Wiley & Sons, Ltd.
Venkataramana Ajjarapu - One of the best experts on this subject based on the ideXlab platform.
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adaptive critical eigenvalues tracing via projected continuation of Invariant Subspace
Iet Generation Transmission & Distribution, 2017Co-Authors: Xiaoru Wang, Venkataramana AjjarapuAbstract:An adaptive power system critical eigenvalues tracing approach based on the projected continuation of Invariant Subspace (CIS) is proposed in this study. The proposed method reduces problem size by applying projections to Invariant Subspace corresponding to critical eigenvalues to ensure efficiency. An adaptive update strategy is adopted to detect and include new critical eigenvalues, ensuring that eigenvalues of interest are always traced. Testing on New England 39- and IEEE-118 bus systems shows that the proposed approach can detect and trace new critical eigenvalues as soon as they emerge and immediately find bifurcation, thus avoiding missing instability information. It also shows that the proposed approach has an advantage in terms of computational time.
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Invariant Subspace based eigenvalue tracing for power system small signal stability analysis
Power and Energy Society General Meeting, 2009Co-Authors: Venkataramana AjjarapuAbstract:This paper presents a novel eigenvalue computation tool for eigenvalue tracing and stability margin identification of power systems. It provides us advanced features for the small-signal stability analysis as well as improved capabilities for eigenvalue analysis. The algorithm is based on the combination of Invariant Subspace method and the predictor-corrector scheme. As a result, one can trace any specified set of eigenvalues of interest. The application of eigenvalue tracing to identify various dynamic phenomena is discussed. The eigenvalue and eigenvector sensitivities can also be extracted successively during the continuation process without additional computational cost. An efficient oscillatory stability margin and damping margin identification is described by using the eigenvalue sensitivity information. The numerical results on the New England 39-bus system are described in detail.
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a decoupled time domain simulation method via Invariant Subspace partition for power system analysis
IEEE Transactions on Power Systems, 2006Co-Authors: D Yang, Venkataramana AjjarapuAbstract:A decoupled method is proposed to deal with time-domain simulation for power system dynamic analysis. Traditionally, there are two main categories of numerical integration methods: explicit methods and implicit methods. The implicit methods are numerically stable but require more computational time to solve the nonlinear equations, while explicit methods are relatively efficient but may cause a numerical stability problem. This paper proposes a new hybrid method to take advantage of both explicit and implicit methods based on the Invariant Subspace partition. The original power system equations are decoupled into two parts that correspond to the stiff and nonstiff Subspaces. For the stiff Invariant Subspace, the implicit method is applied to achieve numerical stability, and the explicit method is employed to handle nonstiff Invariant Subspace for the computational efficiency. As a result, the new hybrid method is both numerically stable and efficient. The approach is demonstrated through New England 39-bus and IEEE 118-bus systems.
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Invariant Subspace parametric sensitivity isps of structure preserving power system models
Power Engineering Society Summer Meeting, 1996Co-Authors: Byongjun Lee, Venkataramana AjjarapuAbstract:In this paper, the parametric sensitivities of a structure-preserving power system model are derived. The parametric sensitivities give the sensitivities of an equilibrium point with respect to a particular parameter of interest. A new Invariant Subspace parametric sensitivity (ISPS) is derived by projecting the total parametric sensitivity onto a particular eigenspace of interest. The ISPS provides the sensitivity of system stability. At a particular eigenSubspace, ISPS of all the parameters under consideration are represented by a right eigenvector multiplied by a scalar /spl sigma/. Then the parameter which has the most influence on the Subspace can be determined by selecting the largest value of /spl sigma/. The methodology is applied to a New England 39-bus system to identify components and parameters that are responsible fora possible system instability.
