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1. Comparing the Difficulty of Factorization and Discrete Logarithm: A 240-Digit Experiment

Author

Pierrick Gaudry, Emmanuel Thomé, Fabrice Boudot, Aurore Guillevic, Nadia Heninger, Paul Zimmermann, XLIM (XLIM), Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), Cryptology, arithmetic : algebraic methods for better algorithms (CARAMBA), Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Department of Algorithms, Computation, Image and Geometry (LORIA - ALGO), Laboratoire Lorrain de Recherche en Informatique et ses Applications (LORIA), Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Lorrain de Recherche en Informatique et ses Applications (LORIA), Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), University of California [San Diego] (UC San Diego), University of California (UC), This work was possible thanks to a 32M-hour allocation on the Juwels super-computer from the PRACE research infrastructure.Experiments presented in this paper were carried out using the Grid'5000 testbed, supported by a scientific interest group hosted by Inria and including CNRS, RENATER and several Universities as well as other organizations (see https://www.grid5000.fr).This work was supported by the French 'Ministère de l'Enseignement Supérieur et de la Recherche', by the 'Conseil Régional de Lorraine', by theEuropean Union, through the 'Cyber-Entreprises' project, and by the US National Science Foundation under grant no. 1651344.High Performance Computing resources were partially provided by the EXPLOR centre hosted by the University de Lorraine.Computations carried out at the University of Pennsylvania were performed on Cisco UCS servers donated by Cisco., Daniele Micciancio, Thomas Ristenpart, Grid5000, University of California, Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), This work was possible thanks to a 32M-hour allocation on the Juwels super-computer from the PRACE research infrastructure.Experiments presented in this paper were carried out using the Grid'5000 testbed, supported by a scientific interest group hosted by Inria and including CNRS, RENATER and several Universities as well as other organizations (see https://www.grid5000.fr).This work was supported by the French ``Ministère de l'Enseignement Supérieur et de la Recherche', by the ``Conseil Régional de Lorraine', by theEuropean Union, through the ``Cyber-Entreprises' project, and by the US National Science Foundation under grant no.~1651344.High Performance Computing resources were partially provided by the EXPLOR centre hosted by the University de Lorraine.Computations carried out at the University of Pennsylvania were performed on Cisco UCS servers donated by Cisco., and Daniele Micciancio, Thomas Ristenpart

Subjects
FOS: Computer and information sciences, Computer Science - Cryptography and Security, Computer science, discrete logarithm, Computation, number field sieve, 02 engineering and technology, law.invention, General number field sieve, [INFO.INFO-CR]Computer Science [cs]/Cryptography and Security [cs.CR], Software, cryptanalysis, Factorization, law, 020204 information systems, 0202 electrical engineering, electronic engineering, information engineering, Hardware_ARITHMETICANDLOGICSTRUCTURES, Arithmetic, factoring, business.industry, Numerical digit, Factoring, Discrete logarithm, 020201 artificial intelligence & image processing, Cryptanalysis, business, Cryptography and Security (cs.CR)
Abstract

International audience; We report on two new records: the factorization of RSA-240, a 795-bit number, and a discrete logarithm computation over a 795-bit prime field. Previous records were the factorization of RSA-768 in 2009 and a 768-bit discrete logarithm computation in 2016. Our two computations at the 795-bit level were done using the same hardware and software, and show that computing a discrete logarithm is not much harder than a factorization of the same size. Moreover, thanks to algorithmic variants and well-chosen parameters, our computations were significantly less expensive than anticipated based on previous records.The last page of this paper also reports on the factorization of RSA-250.

Published
2020

2. Calibration Done Right: Noiseless Flush+Flush Attacks

Author

Clementine Maurice, Guillaume Didier, Délégation générale de l'armement (DGA), Ministère de la Défense, Département d'informatique de l'École normale supérieure (DI-ENS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS), Embedded Security and Cryptography / Sécurité cryptographie embarquée (EMSEC), SYSTÈMES LARGE ÉCHELLE (IRISA-D1), Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Université de Bretagne Sud (UBS)-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 Rennes (UNIV-RENNES)-Institut National de Recherche en Informatique et en Automatique (Inria)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-CentraleSupélec-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Bretagne Sud (UBS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Self-adaptation for distributed services and large software systems (SPIRALS), Inria Lille - Nord Europe, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre de Recherche en Informatique, Signal et Automatique de Lille - UMR 9189 (CRIStAL), Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS), This work has been partly funded by the French Direction G´en´erale de l’Armement, and by the ANR-19-CE39-0007 MIAOUS. Some experiments presented in this paper were carried out using the Grid’5000 testbed, supported by a scientific interest group hosted by Inria and including CNRS, RENATER and several Universities as well as other organizations (see https://www.grid5000.fr)., Grid'5000, ANR-19-CE39-0007,MIAOUS,Attaques sur la micro-architecture des systèmes ubiquitaires(2019), Département d'informatique - ENS Paris (DI-ENS), École normale supérieure - Paris (ENS-PSL), Security & PrIvaCY (SPICY), 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 Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Université de Lille-Centrale Lille-Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Centrale Lille-Centre National de la Recherche Scientifique (CNRS)

Subjects
0303 health sciences, Interconnection, Leak, Hardware_MEMORYSTRUCTURES, Computer science, business.industry, Word error rate, 020207 software engineering, 02 engineering and technology, ComputerSystemsOrganization_PROCESSORARCHITECTURES, [INFO.INFO-CR]Computer Science [cs]/Cryptography and Security [cs.CR], 03 medical and health sciences, 0202 electrical engineering, electronic engineering, information engineering, Calibration, Central processing unit, Cache, Line (text file), business, Computer hardware, 030304 developmental biology
Abstract

International audience; Caches leak information through timing measurements and side-channel attacks. Several attack primitives exist with different requirements and trade-offs. Flush+Flush is a stealthy and fast one that uses the timing of the clflush instruction depending on whether a line is cached. We show that the CPU interconnect plays a bigger role than previously thought in these timings and in Flush+Flush error rate. In this paper, we show that a naive implementation that does not account for the topology of the interconnect yields very high error rates, especially on modern CPUs as the number of cores increases. We therefore reverse-engineer this topology and revisit the calibration phase of Flush+ Flush for different attacker models to determine the correct threshold for clflush hits and misses. We show that our method yields closeto-noiseless side-channel attacks by attacking the AES T-tables implementation of OpenSSL, and by building a covert channel. We obtain a maximal capacity of 5.8 Mbit/s with our method, compared to 1.9 Mbit/s with a naive Flush+Flush implementation on an Intel Core i9-9900 CPU.

Published
2021

3. Deep Variational Metric Learning for Transfer of Expressivity in Multispeaker Text to Speech

Author

Vincent Colotte, Ajinkya Kulkarni, Denis Jouvet, Speech Modeling for Facilitating Oral-Based Communication (MULTISPEECH), Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Department of Natural Language Processing & Knowledge Discovery (LORIA - NLPKD), Laboratoire Lorrain de Recherche en Informatique et ses Applications (LORIA), Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Lorrain de Recherche en Informatique et ses Applications (LORIA), Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Experiments presented in this paper were carried out using the Grid5000 testbed, supported by a scientific interest group hosted by Inria and including CNRS, RENATER and several Universities as well as other organizations. (see https://www.grid5000.fr), and Grid'5000

Subjects
Computer science, Speech recognition, deep metric learning, Contrast (statistics), 020206 networking & telecommunications, Speech synthesis, 02 engineering and technology, expressivity, computer.software_genre, Speaker recognition, Autoencoder, [INFO.INFO-CL]Computer Science [cs]/Computation and Language [cs.CL], Identity (music), [INFO.INFO-AI]Computer Science [cs]/Artificial Intelligence [cs.AI], [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, Metric (mathematics), 0202 electrical engineering, electronic engineering, information engineering, variational autoencoder, 020201 artificial intelligence & image processing, Expressivity (genetics), text-to-speech, Representation (mathematics), computer
Abstract

In this paper, we propose an approach relying on multiclass N-pair loss based deep metric learning in recurrent conditional variational autoencoder (RCVAE). We used RCVAE for implementation of multispeaker expressive text-to-speech (TTS) system. The proposed approach condition text-to-speech system on speaker embeddings, and leads to clustering the latent space representation with respect to emotion. The deep metric learning helps to reduce the intra-class variance and increase the inter-class variance in latent space. Thus, we present multiclass N-pair loss to enhance the meaningful representation of the latent space. For representing the speaker, we extracted speaker embed-dings from the x-vector based speaker recognition model trained on speech data from many speakers. To predict the vocoder features, we used RCVAE for the acoustic modeling, in which the model is conditioned on the textual features as well as on the speaker embedding. We transferred the expressivity by using the mean of the latent variables for each emotion to generate expressive speech in different speaker's voices for which no expressive speech data is available. We compared the results with those of the RCVAE model without multiclass N-pair loss as baseline model. The performance measured by mean opinion score (MOS), speaker MOS, and expressive MOS shows that N-pair loss based deep metric learning significantly improves the transfer of expressivity in the target speaker's voice in synthesized speech.

Published
2020

4. Beachcombing on Strips and Islands

Author

Evangelos Bampas, David Ilcinkas, Jurek Czyzowicz, Ralf Klasing, Laboratoire d'Informatique et Systèmes (LIS), Aix Marseille Université (AMU)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Département d'Informatique et d'Ingénierie (DII), Université du Québec en Outaouais (UQO), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB), ANR-11-BS02-0014,DISPLEXITY,Calculabilité et complexité en distribué(2011), ANR-10-IDEX-0003,IDEX BORDEAUX,Initiative d'excellence de l'Université de Bordeaux(2010), See paper for details., and Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Discrete mathematics, Conjecture, General Computer Science, Competitive analysis, Computer science, Generalization, Approximation algorithm, Mobile robot, 020206 networking & telecommunications, 0102 computer and information sciences, 02 engineering and technology, 01 natural sciences, Infimum and supremum, Domain (mathematical analysis), Theoretical Computer Science, Preferred walking speed, Combinatorics, 010201 computation theory & mathematics, Line (geometry), 0202 electrical engineering, electronic engineering, information engineering, Robot, Point (geometry), [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Online algorithm, Mathematics
Abstract

International audience; A group of mobile robots (beachcombers) have to search collectively every point of a given domain. At any given moment, each robot can be in {\em walking mode} or in {\em searching mode}. It is assumed that each robot's maximum allowed searching speed is strictly smaller than its maximum allowed walking speed. A point of the domain is searched if at least one of the robots visits it in searching mode. The Beachcombers' Problem consists in developing efficient {\em schedules} (algorithms) for the robots which collectively search all the points of the given domain as fast as possible. We consider searching schedules in the following one-dimensional geometric domains: the cycle of a known circumference $L$, the finite straight line segment of a known length $L$, and the semi-infinite line $[0,+\infty)$.We first consider the {\em online} Beachcombers' Problem (i.e.~the scenario when the robots do not know in advance the length of the segment to be searched), where the robots are initially collocated at the origin of a semi-infinite line. It is sought to design a schedule $A$ with maximum {\em speed} $S$, defined as $S = \inf_{\ell}{\frac{\ell}{t_A(\ell)}}$, where $t_A(\ell)$ denotes the time when the search of the segment $[0,\ell]$ is completed under $A$. We consider a {\em discrete} and a {\em continuous} version of the problem, depending on whether the infimum is takenover $\ell \in \mathbb{N}^*$ or $\ell \geq 1$. We prove that the $\mathtt{LeapFrog}$ algorithm, which was proposed in [Czyzowicz et al., SIROCCO 2014, LNCS 8576, pp. 23--36 (2014)], is in fact optimal in the discrete case. This settles in the affirmative a conjecture from that paper. We also show how to extend this result to the more general continuous online setting.For the {\em offline} version of the Beachcombers' Problem (i.e.~the scenario when the robots know in advance the length of the segment to be searched), we consider the \emph{$t$-source} Beachcombers' Problem (i.e.~all robots start from a fixed number $t \geq 1$ of starting positions) on the cycle and on the finite segment. For the \emph{$t$-source} Beachcombers' Problem on the cycle, we show that the structure of the optimal solutions is identical to the structure of the optimal solutions to the $2t$-source Beachcombers' Problem on a finite segment. In consequence, by using results from [Czyzowicz et al., ALGOSENSORS 2014, LNCS 8847, pp.~3--21 (2014)], we prove that the \emph{1-source} Beachcombers' Problem on the cycle is NP-hard, and we derive approximation algorithms for the problem. For the \emph{$t$-source} variant of the Beachcombers' Problem on the cycle and on the finite segment, we also derive efficient approximation algorithms.One important contribution of our work is that, in all variants of the offline Beachcombers' Problem that we discuss, we allow the robots to \emph{change direction of movement} and search points of the domain on both sides of their respective starting positions. This represents a significant generalization compared to the model considered in~[Czyzowicz et al., ALGOSENSORS 2014, LNCS 8847, pp. 3--21 (2014)], in which each robot had a fixed direction of movement that was specified as part of the solution to the problem. We manage to prove that changes of direction do not help the robots achieve optimality.

Published
2015

5. Disconnected Components Detection and Rooted Shortest-Path Tree Maintenance in Networks

Author

Christian Glacet, Nicolas Hanusse, Colette Johnen, David Ilcinkas, Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB), ANR-16-CE40-0023,DESCARTES,Abstraction modulaire pour le calcul distribué(2016), ANR-16-CE25-0009,ESTATE,Auto-stabilisation et amélioration de la sûreté dans les environnements distribués évoluant dans le temps(2016), ANR-10-IDEX-0003,IDEX BORDEAUX,Initiative d'excellence de l'Université de Bordeaux(2010), See paper for details., and ANR-11-BS02-0014,DISPLEXITY,Calculabilité et complexité en distribué(2011)

Subjects
Routing protocol, Leader election, Theoretical computer science, Computer Networks and Communications, Computer science, 02 engineering and technology, Theoretical Computer Science, Artificial Intelligence, shortest-path, disconnected network, Node (computer science), 0202 electrical engineering, electronic engineering, information engineering, Mathematics, Discrete mathematics, Connected component, routing algorithm, business.industry, Shortest-path tree, 020206 networking & telecommunications, Task (computing), Tree (data structure), self-stabilization, Hardware and Architecture, Asynchronous communication, Shortest path problem, 020201 artificial intelligence & image processing, Enhanced Data Rates for GSM Evolution, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Daemon, business, Software, Computer network
Abstract

Many articles deal with the problem of maintaining a rooted shortest-path tree. However, after some edge deletions, some nodes can be disconnected from the connected component V r of some distinguished node r . In this case, an additional objective is to ensure the detection of the disconnection by the nodes that no longer belong to V r . We present a detailed analysis of a silent self-stabilizing algorithm. We prove that it solves this more demanding task in anonymous weighted networks with the following additional strong properties: it runs without any knowledge on the network and under the unfair daemon, that is without any assumption on the asynchronous model. Moreover, it terminates in less than 2 n + D rounds for a network of n nodes and hop-diameter D .

Published
2014

6. Exploration of Constantly Connected Dynamic Graphs Based on Cactuses

Author

Ahmed Mouhamadou Wade, David Ilcinkas, Ralf Klasing, Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB), See papers for details., and ANR-11-BS02-0014,DISPLEXITY,Calculabilité et complexité en distribué(2011)

Subjects
Mobile agent, Block graph, Discrete mathematics, Symmetric graph, Cactus graph, 0102 computer and information sciences, 02 engineering and technology, 01 natural sciences, law.invention, Combinatorics, Connectivity over time, 010201 computation theory & mathematics, law, Random regular graph, Clique-width, Line graph, 0202 electrical engineering, electronic engineering, information engineering, 020201 artificial intelligence & image processing, Exploration, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Pancyclic graph, Dynamic graphs, MathematicsofComputing_DISCRETEMATHEMATICS, Mathematics, Distance-hereditary graph
Abstract

International audience; We study the problem of exploration by a mobile entity (agent) of a class of dynamic networks, namely constantly connected dynamic graphs. This problem has already been studied in the case where the agent knows the dynamics of the graph and the underlying graph is a ring of $n$ vertices \cite{IW13}. In this paper, we consider the same problem and we suppose that the underlying graph is a cactus graph (a connected graph in which any two simple cycles have at most one vertex in common). We propose an algorithm that allows the agent to explore these dynamic graphs in at most $2^{O(\sqrt{\log n})} n$ time units. We show that the lower bound of the algorithm is $2^{\Omega(\sqrt{\log n})} n$ time units.

Published
2014

7. Cultivation of hierarchical 3D scaffolds inside a perfusion bioreactor: scaffold design and finite-element analysis of fluid flow.

Author

Sampson K, Koo S, Gadola C, Vasiukhina A, Singh A, Spartano A, Gollapudi R, Duley M, Mueller J, James PF, and Yousefi AM

Abstract

The use of porous 3D scaffolds for the repair of bone nonunion and osteoporotic bone is currently an area of great interest. Using a combination of thermally-induced phase separation (TIPS) and 3D-plotting (3DP), we have generated hierarchical 3DP/TIPS scaffolds made of poly(lactic-co-glycolic acid) (PLGA) and nanohydroxyapatite (nHA). A full factorial design of experiments was conducted, in which the PLGA and nHA compositions were varied between 6-12% w/v and 10-40% w/w, respectively, totaling 16 scaffold formulations with an overall porosity ranging between 87%-93%. These formulations included an optimal scaffold design identified in our previous study. The internal structures of the scaffolds were examined using scanning electron microscopy and microcomputed tomography. Our optimal scaffold was seeded with MC3T3-E1 murine preosteoblastic cells and subjected to cell culture inside a tissue culture dish and a perfusion bioreactor. The results were compared to those of a commercial CellCeram™ scaffold with a composition of 40% β-tricalcium phosphate and 60% hydroxyapatite (β-TCP/HA). Media flow within the macrochannels of 3DP/TIPS scaffolds was modeled in COMSOL software in order to fine tune the wall shear stress. CyQUANT DNA assay was performed to assess cell proliferation. The normalized number of cells for the optimal scaffold was more than twofold that of CellCeram™ scaffold after two weeks of culture inside the bioreactor. Despite the substantial variability in the results, the observed improvement in cell proliferation upon culture inside the perfusion bioreactor (vs. static culture) demonstrated the role of macrochannels in making the 3DP/TIPS scaffolds a promising candidate for scaffold-based tissue engineering., Competing Interests: Declarations Conflicts of interest/Competing interests: The authors declare that there are no conflicts of interest or competing interests.

Published
2021
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