Filters








18 Hits in 0.89 sec

Statistical Decoding [article]

Thomas Debris-Alazard, Jean-Pierre Tillich
2017 arXiv   pre-print
The security of code-based cryptography relies primarily on the hardness of generic decoding with linear codes. The best generic decoding algorithms are all improvements of an old algorithm due to Prange: they are known under the name of information set decoding techniques (ISD). A while ago a generic decoding algorithm which does not belong to this family was proposed: statistical decoding. It is a randomized algorithm that requires the computation of a large set of parity-check equations of
more » ... heck equations of moderate weight. We solve here several open problems related to this decoding algorithm. We give in particular the asymptotic complexity of this algorithm, give a rather efficient way of computing the parity-check equations needed for it inspired by ISD techniques and give a lower bound on its complexity showing that when it comes to decoding on the Gilbert-Varshamov bound it can never be better than Prange's algorithm.
arXiv:1701.07416v2 fatcat:z6hlxk65zbggjkgrdnd2hczhay

Statistical decoding

Thomas Debris-Alazard, Jean-Pierre Tillich
2017 2017 IEEE International Symposium on Information Theory (ISIT)  
The security of code-based cryptography relies primarily on the hardness of generic decoding with linear codes. The best generic decoding algorithms are all improvements of an old algorithm due to Prange: they are known under the name of information set decoding techniques (ISD). A while ago a generic decoding algorithm which does not belong to this family was proposed: statistical decoding. It is a randomized algorithm that requires the computation of a large set of parity-check equations of
more » ... heck equations of moderate weight. We solve here several open problems related to this decoding algorithm. We give in particular the asymptotic complexity of this algorithm, give a rather efficient way of computing the parity-check equations needed for it inspired by ISD techniques and give a lower bound on its complexity showing that when it comes to decoding on the Gilbert-Varshamov bound it can never be better than Prange's algorithm.
doi:10.1109/isit.2017.8006839 dblp:conf/isit/Debris-AlazardT17 fatcat:sjvvgbnb6rdnlbb6mc6ntsbc64

Ternary Syndrome Decoding with Large Weight [article]

Rémi Bricout, André Chailloux, Thomas Debris-Alazard, Matthieu Lequesne
2019 arXiv   pre-print
The Syndrome Decoding problem is at the core of many code-based cryptosystems. In this paper, we study ternary Syndrome Decoding in large weight. This problem has been introduced in the Wave signature scheme but has never been thoroughly studied. We perform an algorithmic study of this problem which results in an update of the Wave parameters. On a more fundamental level, we show that ternary Syndrome Decoding with large weight is a really harder problem than the binary Syndrome Decoding
more » ... ome Decoding problem, which could have several applications for the design of code-based cryptosystems.
arXiv:1903.07464v2 fatcat:cefqe43yvngjrhobicpbikwjee

Quantum Reduction of Finding Short Code Vectors to the Decoding Problem [article]

Thomas Debris-Alazard, Maxime Remaud, Jean-Pierre Tillich
2021 arXiv   pre-print
We give a quantum reduction from finding short codewords in a random linear code to decoding for the Hamming metric. This is the first time such a reduction (classical or quantum) has been obtained. Our reduction adapts to linear codes Stehlé-Steinfield-Tanaka-Xagawa' re-interpretation of Regev's quantum reduction from finding short lattice vectors to solving the Closest Vector Problem. The Hamming metric is a much coarser metric than the Euclidean metric and this adaptation has needed several
more » ... has needed several new ingredients to make it work. For instance, in order to have a meaningful reduction it is necessary in the Hamming metric to choose a very large decoding radius and this needs in many cases to go beyond the radius where decoding is unique. Another crucial step for the analysis of the reduction is the choice of the errors that are being fed to the decoding algorithm. For lattices, errors are usually sampled according to a Gaussian distribution. However, it turns out that the Bernoulli distribution (the analogue for codes of the Gaussian) is too much spread out and can not be used for the reduction with codes. Instead we choose here the uniform distribution over errors of a fixed weight and bring in orthogonal polynomials tools to perform the analysis and an additional amplitude amplification step to obtain the aforementioned result.
arXiv:2106.02747v1 fatcat:uxip7adgk5dyhklt3dug3kupk4

A tight security reduction in the quantum random oracle model for code-based signature schemes [article]

André Chailloux, Thomas Debris-Alazard
2017 arXiv   pre-print
Quantum secure signature schemes have a lot of attention recently, in particular because of the NIST call to standardize quantum safe cryptography. However, only few signature schemes can have concrete quantum security because of technical difficulties associated with the Quantum Random Oracle Model (QROM). In this paper, we show that code-based signature schemes based on the full domain hash paradigm can behave very well in the QROM i.e. that we can have tight security reductions. We also
more » ... tions. We also study quantum algorithms related to the underlying code-based assumption. Finally, we apply our reduction to a concrete example: the SURF signature scheme. We provide parameters for 128 bits of quantum security in the QROM and show that the obtained parameters are competitive compared to other similar quantum secure signature schemes.
arXiv:1709.06870v1 fatcat:xeefupp6pra2xhmtz2ccvyt5ny

Two Attacks on Rank Metric Code-Based Schemes: RankSign and an IBE Scheme [chapter]

Thomas Debris-Alazard, Jean-Pierre Tillich
2018 Lecture Notes in Computer Science  
RankSign [29] is a code-based signature scheme proposed to the NIST competition for quantum-safe cryptography [5] and, moreover, is a fundamental building block of a new Identity-Based-Encryption (IBE) [25] . This signature scheme is based on the rank metric and enjoys remarkably small key sizes, about 10KBytes for an intended level of security of 128 bits. Unfortunately we will show that all the parameters proposed for this scheme in [5] can be broken by an algebraic attack that exploits the
more » ... that exploits the fact that the augmented LRPC codes used in this scheme have very low weight codewords. Therefore, without RankSign the IBE cannot be instantiated at this time. As a second contribution we will show that the problem is deeper than finding a new signature in rankbased cryptography, we also found an attack on the generic problem upon which its security reduction relies. However, contrarily to the RankSign scheme, it seems that the parameters of the IBE scheme could be chosen in order to avoid our attack. Finally, we have also shown that if one replaces the rank metric in the [25] IBE scheme by the Hamming metric, then a devastating attack can be found.
doi:10.1007/978-3-030-03326-2_3 fatcat:zh2tgmo7ivhkto3omjcmkulfke

The problem with the SURF scheme [article]

Thomas Debris-Alazard, Nicolas Sendrier, Jean-Pierre Tillich
2017 arXiv   pre-print
There is a serious problem with one of the assumptions made in the security proof of the SURF scheme. This problem turns out to be easy in the regime of parameters needed for the SURF scheme to work. We give afterwards the old version of the paper for the reader's convenience.
arXiv:1706.08065v4 fatcat:6bwz4u5kbff2napx33zbpnmmem

Classical and Quantum algorithms for generic Syndrome Decoding problems and applications to the Lee metric [article]

André Chailloux, Thomas Debris-Alazard, Simona Etinski
2021 arXiv   pre-print
The security of code-based cryptography usually relies on the hardness of the syndrome decoding (SD) problem for the Hamming weight. The best generic algorithms are all improvements of an old algorithm by Prange, and they are known under the name of Information Set Decoding (ISD) algorithms. This work aims to extend ISD algorithms' scope by changing the underlying weight function and alphabet size of SD. More precisely, we show how to use Wagner's algorithm in the ISD framework to solve SD for
more » ... rk to solve SD for a wide range of weight functions. We also calculate the asymptotic complexities of ISD algorithms both in the classical and quantum case. We then apply our results to the Lee metric, which currently receives a significant amount of attention. By providing the parameters of SD for which decoding in the Lee weight seems to be the hardest, our study could have several applications for designing code-based cryptosystems and their security analysis, especially against quantum adversaries.
arXiv:2104.12810v2 fatcat:olihfyyyszazhfp32qjza4y6sq

Two attacks on rank metric code-based schemes: RankSign and an Identity-Based-Encryption scheme [article]

Thomas Debris-Alazard, Jean-Pierre Tillich
2018 arXiv   pre-print
RankSign [GRSZ14a] is a code-based signature scheme proposed to the NIST competition for quantum-safe cryptography [AGHRZ17] and, moreover, is a fundamental building block of a new Identity-Based-Encryption (IBE) [GHPT17a]. This signature scheme is based on the rank metric and enjoys remarkably small key sizes, about 10KBytes for an intended level of security of 128 bits. Unfortunately we will show that all the parameters proposed for this scheme in [AGHRZ17] can be broken by an algebraic
more » ... an algebraic attack that exploits the fact that the augmented LRPC codes used in this scheme have very low weight codewords. Therefore, without RankSign the IBE cannot be instantiated at this time. As a second contribution we will show that the problem is deeper than finding a new signature in rank-based cryptography, we also found an attack on the generic problem upon which its security reduction relies. However, contrarily to the RankSign scheme, it seems that the parameters of the IBE scheme could be chosen in order to avoid our attack. Finally, we have also shown that if one replaces the rank metric in the [GHPT17a] IBE scheme by the Hamming metric, then a devastating attack can be found.
arXiv:1804.02556v2 fatcat:bypwdkfv5zhizgigg7lir574fq

Wave: A New Family of Trapdoor One-Way Preimage Sampleable Functions Based on Codes [article]

Thomas Debris-Alazard and Nicolas Sendrier and Jean-Pierre Tillich
2019 arXiv   pre-print
We present here a new family of trapdoor one-way Preimage Sampleable Functions (PSF) based on codes, the Wave-PSF family. The trapdoor function is one-way under two computational assumptions: the hardness of generic decoding for high weights and the indistinguishability of generalized (U,U+V)-codes. Our proof follows the GPV strategy [GPV08]. By including rejection sampling, we ensure the proper distribution for the trapdoor inverse output. The domain sampling property of our family is ensured
more » ... family is ensured by using and proving a variant of the left-over hash lemma. We instantiate the new Wave-PSF family with ternary generalized (U,U+V)-codes to design a "hash-and-sign" signature scheme which achieves existential unforgeability under adaptive chosen message attacks (EUF-CMA) in the random oracle model. For 128 bits of classical security, signature sizes are in the order of 15 thousand bits, the public key size in the order of 4 megabytes, and the rejection rate is limited to one rejection every 10 to 12 signatures.
arXiv:1810.07554v2 fatcat:7cxwckxrergffcwcccx22odc7q

Nonpigmented and Bacteriochlorophyll-Containing Bradyrhizobia Isolated from Aeschynomene indica

P van Berkum, R E Tully, D L Keister
1995 Applied and Environmental Microbiology  
Alazard, Appl. Environ. Microbiol. 50:732-734, 1985), since they did not nodulate Aeschynomene americana or Macroptilium atropurpureum.  ...  Bchl was extracted with acetone-methanol (7:2, vol/vol), and after centrifugation to remove insoluble debris, the concentration was determined, using an extinction coefficient of 75 mM/cm (5) .  ...  The soil samples (10 to 50 g) were collected into small, sterile plastic bags (Whirl-Pak Bags; Thomas Scientific, Swedesboro, N.J.) and upon receipt were stored at 4ЊC for less than 1 month before use.  ... 
doi:10.1128/aem.61.2.623-629.1995 fatcat:np4vzsehhbbbxkvlayuj7ebpai

Robust line-of-sight pointing control on-board a stratospheric balloon-borne platform [article]

Ervan Kassarian, Francesco Sanfedino, Daniel Alazard, Johan Montel, Charles-Antoine Chevrier
2021 arXiv   pre-print
DOI: 10.1016/j.ast.2021.106607. [17] Ervan Kassarian, Francesco Sanfedino, Daniel Alazard, Charles-Antoine Chevrier, and Johan Montel.  ...  Modeling and Control of a Flexible Space Robot to Capture a Tumbling Debris. PhD thesis, Ecole Polytechnique de Montréal, 2016. 17  ... 
arXiv:2112.10458v1 fatcat:tgtdemgv2zd5pnldfqs5ogxpry

Generation of Alkalinity by Stimulation of Microbial Iron Reduction in Acid Rock Drainage Systems: Impact of Natural Organic Matter Types

Martha E. Jimenez-Castaneda, Carolina Scarinci, Adam Burke, Christopher Boothman, David J. Vaughan, Jonathan R. Lloyd, Bart E. van Dongen
2020 Water, Air and Soil Pollution  
Clostridia are capable of fermenting or degrading plant polysaccharides, involving the use of enzymes such as cellulases and xylanases (Cornet et al. 1983; Kato et al. 2004; Thomas et al. 2014) .  ...  Fig. 1 a 1 Location map and relevant geology of the Mam Tor landslide and b the cross section A-A′ shows the Mam Tor beds and the Edale Shales; the scarp zone, transition zone and low debris zone of the  ... 
doi:10.1007/s11270-020-04820-7 fatcat:t742efvx7bamvbpwbf2dkaq2ca

Natural Water Treatment Systems for Safe and Sustainable Water Supply in the Indian Context: Saph Pani

Thomas Wintgens
2015 Water Intelligence Online  
This latter point is further discussed in Alazard et al. (2015) .  ...  The terrain around the tube-wells gently slopes and consists of debris from recurrent landslides that took place from 1867-1924.  ... 
doi:10.2166/9781780407111 fatcat:yvxypfqu2jhdtchlfgsgwl7fgq

Le Corbusier, negotiating modernity: representing Algiers, 1930-42

Frances Sherry McKay
1994
Alazard, 391 "L'Architecture et l'Urbanisme a Alger de 1918 a 1936," Architecture (15 Jan. 1937): 23. Figure 50 . 50 Le Corbusier.  ...  "Thomas Geoffrey August, "Colonial Policy and Propaganda: The Popularization of the Idée Coloniale in France, 1919 ," diss.., University of Wisconsin-Madison, 1978 12 Anne Ruel, "L'Invention de Ia Médit  ... 
doi:10.14288/1.0088304 fatcat:xgxejqpo7za3bpzpmzsapfgaby
« Previous Showing results 1 — 15 out of 18 results