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21 results on '"Lambin, Baptiste"'

1. Pitfalls and Shortcomings for Decompositions and Alignment

Author

Lambin, Baptiste, Leander, Gregor, Neumann, Patrick, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Hazay, Carmit, editor, and Stam, Martijn, editor

Published
2023
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3. Strong and Tight Security Guarantees Against Integral Distinguishers

Author

Hebborn, Phil, Lambin, Baptiste, Leander, Gregor, Todo, Yosuke, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Tibouchi, Mehdi, editor, and Wang, Huaxiong, editor

Published
2021
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4. PRINCEv2 : More Security for (Almost) No Overhead

Author

Božilov, Dušan, Eichlseder, Maria, Knežević, Miroslav, Lambin, Baptiste, Leander, Gregor, Moos, Thorben, Nikov, Ventzislav, Rasoolzadeh, Shahram, Todo, Yosuke, Wiemer, Friedrich, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Dunkelman, Orr, editor, Jacobson, Jr., Michael J., editor, and O'Flynn, Colin, editor

Published
2021
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5. Lower Bounds on the Degree of Block Ciphers

Author

Hebborn, Phil, Lambin, Baptiste, Leander, Gregor, Todo, Yosuke, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Moriai, Shiho, editor, and Wang, Huaxiong, editor

Published
2020
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6. Variants of the AES Key Schedule for Better Truncated Differential Bounds

Author

Derbez, Patrick, Fouque, Pierre-Alain, Jean, Jérémy, Lambin, Baptiste, Hutchison, David, Series Editor, Kanade, Takeo, Series Editor, Kittler, Josef, Series Editor, Kleinberg, Jon M., Series Editor, Mattern, Friedemann, Series Editor, Mitchell, John C., Series Editor, Naor, Moni, Series Editor, Pandu Rangan, C., Series Editor, Steffen, Bernhard, Series Editor, Terzopoulos, Demetri, Series Editor, Tygar, Doug, Series Editor, Cid, Carlos, editor, and Jacobson Jr., Michael J., editor

Published
2019
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8. PRINCEv2

Author

Božilov, Dušan, primary, Eichlseder, Maria, additional, Knežević, Miroslav, additional, Lambin, Baptiste, additional, Leander, Gregor, additional, Moos, Thorben, additional, Nikov, Ventzislav, additional, Rasoolzadeh, Shahram, additional, Todo, Yosuke, additional, and Wiemer, Friedrich, additional

Published
2021
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12. Cryptanalysis of ARX-based White-box Implementations

Author

Fonds National de la Recherche - FnR [sponsor], Biryukov, Alexei, Lambin, Baptiste, Udovenko, Aleksei, Fonds National de la Recherche - FnR [sponsor], Biryukov, Alexei, Lambin, Baptiste, and Udovenko, Aleksei

Abstract

At CRYPTO’22, Ranea, Vandersmissen, and Preneel proposed a new way to design white-box implementations of ARX-based ciphers using so-called implicit functions and quadratic-affine encodings. They suggest the Speck block-cipher as an example target. In this work, we describe practical attacks on the construction. For the implementation without one of the external encodings, we describe a simple algebraic key recovery attack. If both external encodings are used (the main scenario suggested by the authors), we propose optimization and inversion attacks, followed by our main result - a multiple-step round decomposition attack and a decomposition-based key recovery attack. Our attacks only use the white-box round functions as oracles and do not rely on their description. We implemented and verified experimentally attacks on white-box instances of Speck-32/64 and Speck-64/128. We conclude that a single ARX-round is too weak to be used as a white-box round.

Published
2023

13. Cryptanalysis of ARX-based White-box Implementations

Author

Biryukov, Alexei, Lambin, Baptiste, Udovenko, Aleksei, and Fonds National de la Recherche - FnR [sponsor]

Subjects
Cryptanalysis, Computer science [C05] [Engineering, computing & technology], Decomposition attacks, Sciences informatiques [C05] [Ingénierie, informatique & technologie], Algebraic attacks, White-box cryptography
Abstract

At CRYPTO’22, Ranea, Vandersmissen, and Preneel proposed a new way to design white-box implementations of ARX-based ciphers using so-called implicit functions and quadratic-affine encodings. They suggest the Speck block-cipher as an example target. In this work, we describe practical attacks on the construction. For the implementation without one of the external encodings, we describe a simple algebraic key recovery attack. If both external encodings are used (the main scenario suggested by the authors), we propose optimization and inversion attacks, followed by our main result - a multiple-step round decomposition attack and a decomposition-based key recovery attack. Our attacks only use the white-box round functions as oracles and do not rely on their description. We implemented and verified experimentally attacks on white-box instances of Speck-32/64 and Speck-64/128. We conclude that a single ARX-round is too weak to be used as a white-box round.

Published
2023

15. Linearly equivalent S-boxes and the division property

Author

Lambin, Baptiste (Dr.), Derbez, Patrick, and Fouque, Pierre-Alain

Subjects
ddc:004
Abstract

Division property is a cryptanalysis method that proves to be very efficient on block ciphers. Computer-aided techniques such as MILP have been widely and successfully used to study various cryptanalysis techniques, and it especially led to many new results for the division property. Nonetheless, we claim that the previous techniques do not consider the full search space. We show that even if the previous techniques fail to find a distinguisher based on the division property over a given function, we can potentially find a relevant distinguisher over a linearly equivalent function. We show that the representation of the block cipher heavily influences the propagation of the division property, and exploiting this, we give an algorithm to efficiently search for such linear mappings. As a result, we exhibit a new distinguisher over 10 rounds of RECTANGLE, while the previous best was over 9 rounds, and rule out such a distinguisher over more than 9 rounds of PRESENT. We also give some insight about the construction of an S-box to strengthen a block cipher against our technique. We prove that using an S-box satisfying a certain criterion is optimal in term of resistance against classical division property. Accordingly, we exhibit stronger variants of RECTANGLE and PRESENT, improving the resistance against division property based distinguishers by 2 rounds.

Published
2020

16. Optimisation des principaux composants des chiffrements par bloc

Author

Lambin, Baptiste, Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), EMbedded SEcurity and Cryptography (EMSEC), SYSTÈMES LARGE ÉCHELLE (IRISA-D1), CentraleSupélec-Télécom Bretagne-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de Recherche en Informatique et en Automatique (Inria)-École normale supérieure - Rennes (ENS Rennes)-Université de Bretagne Sud (UBS)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Télécom Bretagne-Université de Rennes 1 (UR1), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), Université Rennes 1, Pierre-Alain Fouque, Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes

Subjects
Cryptanalysis, [INFO.INFO-CR]Computer Science [cs]/Cryptography and Security [cs.CR], Design, Cryptography, Optimisation, Cryptographie, Cryptanalyse, Conception
Abstract

Along with new cryptanalysis techniques, the security of block ciphers is always evolving. When designing new block ciphers, we thus need to consider these new techniques during the security analysis. In this thesis, we show how to build some core operations for block ciphers to improve the security against some attacks. We first start by describing a method to find optimal (according to some criterion) even-odd permutations for a Generalized Feistel Network. Using a new characterization and an efficient algorithm, we are able to solve a 10-years old problem. We then give new cryptanalysis techniques to improve the division property, along with a new proven optimal criterion for designing S-boxes. We continue with new observations for the design of an alternative key-schedule for AES. We thus give a new key-schedule, which is both more efficient and more secure against some attacks compared to the original one. Finally, we describe a very efficient generic algorithm to break most proposals in white-box cryptography, as well as a dedicated attack on a previously not analyzed scheme, leading to a key-recovery attack in a few seconds.; La sécurité des chiffrements par bloc évolue constamment au fur et à mesure que de nouvelles techniques de cryptanalyse sont découvertes. Lors de la conception de nouveaux chiffrements par bloc, il est donc nécessaire de considérer ces nouvelles techniques dans l'analyse de sécurité. Dans cette thèse, nous montrons comment construire certaines opérations internes des chiffrements par bloc pour améliorer la résistance à certaines attaques. Nous commençons par donner une méthode pour trouver les permutations paires-impaires optimales selon un certain critère pour les Réseaux de Feistel Généralisés. Grâce à une nouvelle caractérisation et à un algorithme efficace, nous sommes notamment capables de résoudre un problème ouvert depuis 10 ans. Nous donnons ensuite de nouvelles techniques de cryptanalyse pour améliorer la division property, qui nous permet également de donner un nouveau critère optimal pour la conception de boîtes-S. Nous continuons avec de nouvelles observations pour un cadencement de clé alternatif pour AES. Ceci nous permet de donner un nouveau cadencement de clé, à la fois plus efficace et augmentant la sécurité face à certaines attaques par rapport à l’original. Pour finir, nous présentons un algorithme général très effiace permettant d’attaquer la majorité des propositions pour la cryptographie en boîte blanche, ainsi qu’une attaque dédiée sur un schéma non attaqué jusque là, donnant lieu à une attaque qui n’a besoin que de quelques secondes pour retrouver la clé.

Published
2019

20. Efficient Search for Optimal Diffusion Layers of Generalized Feistel Networks

Author

Patrick Derbez, Pierre-Alain Fouque, Baptiste Lambin, Victor Mollimard, EMbedded SEcurity and Cryptography (EMSEC), SYSTÈMES LARGE ÉCHELLE (IRISA-D1), Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR), ANR-17-CE39-0003,CryptAudit,Conception d'outils d'audit de primitives cryptographiques(2017), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UNIV-RENNES), Lambin, Baptiste, and Conception d'outils d'audit de primitives cryptographiques - - CryptAudit2017 - ANR-17-CE39-0003 - AAPG2017 - VALID

Subjects
lcsh:Computer engineering. Computer hardware, Applied Mathematics, Permutations, lcsh:TK7885-7895, 020206 networking & telecommunications, 0102 computer and information sciences, 02 engineering and technology, 01 natural sciences, Diffusion round, Computer Science Applications, Computational Mathematics, [INFO.INFO-CR]Computer Science [cs]/Cryptography and Security [cs.CR], 010201 computation theory & mathematics, Feistel, 0202 electrical engineering, electronic engineering, information engineering, Software, ComputingMilieux_MISCELLANEOUS, [INFO.INFO-CR] Computer Science [cs]/Cryptography and Security [cs.CR]
Abstract

The Feistel construction is one of the most studied ways of building block ciphers. Several generalizations were then proposed in the literature, leading to the Generalized Feistel Network, where the round function first applies a classical Feistel operation in parallel on an even number of blocks, and then a permutation is applied to this set of blocks. In 2010 at FSE, Suzaki and Minematsu studied the diffusion of such construction, raising the question of how many rounds are required so that each block of the ciphertext depends on all blocks of the plaintext. They thus gave some optimal permutations, with respect to this diffusion criteria, for a Generalized Feistel Network consisting of 2 to 16 blocks, as well as giving a good candidate for 32 blocks. Later at FSE’19, Cauchois et al. went further and were able to propose optimal even-odd permutations for up to 26 blocks. In this paper, we complete the literature by building optimal even-odd permutations for 28, 30, 32, 36 blocks which to the best of our knowledge were unknown until now. The main idea behind our constructions and impossibility proof is a new characterization of the total diffusion of a permutation after a given number of rounds. In fact, we propose an efficient algorithm based on this new characterization which constructs all optimal even-odd permutations for the 28, 30, 32, 36 blocks cases and proves a better lower bound for the 34, 38, 40 and 42 blocks cases. In particular, we improve the 32 blocks case by exhibiting optimal even-odd permutations with diffusion round of 9. The existence of such a permutation was an open problem for almost 10 years and the best known permutation in the literature had a diffusion round of 10. Moreover, our characterization can be implemented very efficiently and allows us to easily re-find all optimal even-odd permutations for up to 26 blocks with a basic exhaustive search, IACR Transactions on Symmetric Cryptology, Volume 2019, Issue 2

Published
2019

21. On Recovering Affine Encodings in White-Box Implementations

Author

Patrick Derbez, Pierre-Alain Fouque, Baptiste Lambin, Brice Minaud, EMbedded SEcurity and Cryptography (EMSEC), SYSTÈMES LARGE ÉCHELLE (IRISA-D1), Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), CentraleSupélec-Télécom Bretagne-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de Recherche en Informatique et en Automatique (Inria)-École normale supérieure - Rennes (ENS Rennes)-Université de Bretagne Sud (UBS)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-CentraleSupélec-Télécom Bretagne-Université de Rennes 1 (UR1), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), Royal Holloway [University of London] (RHUL), ANR-17-CE39-0003,CryptAudit,Conception d'outils d'audit de primitives cryptographiques(2017), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-Télécom Bretagne-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Lambin, Baptiste, and Conception d'outils d'audit de primitives cryptographiques - - CryptAudit2017 - ANR-17-CE39-0003 - AAPG2017 - VALID

Subjects
060201 languages & linguistics, AES, lcsh:Computer engineering. Computer hardware, lcsh:T58.5-58.64, lcsh:Information technology, lcsh:TK7885-7895, 06 humanities and the arts, 02 engineering and technology, Cryptanalysis, [INFO.INFO-CR]Computer Science [cs]/Cryptography and Security [cs.CR], 0602 languages and literature, 0202 electrical engineering, electronic engineering, information engineering, 020201 artificial intelligence & image processing, ComputingMilieux_MISCELLANEOUS, [INFO.INFO-CR] Computer Science [cs]/Cryptography and Security [cs.CR], White-Box Cryptography
Abstract

Ever since the first candidate white-box implementations by Chow et al. in 2002, producing a secure white-box implementation of AES has remained an enduring challenge. Following the footsteps of the original proposal by Chow et al., other constructions were later built around the same framework. In this framework, the round function of the cipher is “encoded” by composing it with non-linear and affine layers known as encodings. However, all such attempts were broken by a series of increasingly efficient attacks that are able to peel off these encodings, eventually uncovering the underlying round function, and with it the secret key. These attacks, however, were generally ad-hoc and did not enjoy a wide applicability. As our main contribution, we propose a generic and efficient algorithm to recover affine encodings, for any Substitution-Permutation-Network (SPN) cipher, such as AES, and any form of affine encoding. For AES parameters, namely 128-bit blocks split into 16 parallel 8-bit S-boxes, affine encodings are recovered with a time complexity estimated at 232 basic operations, independently of how the encodings are built. This algorithm is directly applicable to a large class of schemes. We illustrate this on a recent proposal due to Baek, Cheon and Hong, which was not previously analyzed. While Baek et al. evaluate the security of their scheme to 110 bits, a direct application of our generic algorithm is able to break the scheme with an estimated time complexity of only 235 basic operations. As a second contribution, we show a different approach to cryptanalyzing the Baek et al. scheme, which reduces the analysis to a standalone combinatorial problem, ultimately achieving key recovery in time complexity 231. We also provide an implementation of the attack, which is able to recover the secret key in about 12 seconds on a standard desktop computer., IACR Transactions on Cryptographic Hardware and Embedded Systems, Volume 2018, Issue 3

Published
2018

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