223 research outputs found
Multipartite entanglement, quantum-error-correcting codes, and entangling power of quantum evolutions
We investigate the average bipartite entanglement, over all possible
divisions of a multipartite system, as a useful measure of multipartite
entanglement. We expose a connection between such measures and
quantum-error-correcting codes by deriving a formula relating the weight
distribution of the code to the average entanglement of encoded states.
Multipartite entangling power of quantum evolutions is also investigated.Comment: 13 pages, 1 figur
Two attacks on rank metric code-based schemes: RankSign and an Identity-Based-Encryption scheme
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 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
\u3ci\u3es\u3c/i\u3e-Extremal Additive \u3cb\u3eF\u3csub\u3e4\u3c/sub\u3e\u3c/b\u3e Codes
Binary self-dual codes and additive self-dual codes over F4 have in common interesting properties, for example, Type I, Type II, shadows, etc. Recently Bachoc and Gaborit introduced the notion of s-extremality for binary self-dual codes, generalizing Elkies\u27 study on the highest possible minimum weight of the shadows of binary self-dual codes. In this paper, we introduce a concept of s-extremality for additive self-dual codes over F4, give a bound on the length of these codes with even distance d, classify them up to minimum distance d = 4, give possible lengths and (shadow) weight enumerators for which there exist s-extremal codes with 5 ≤ d ≤ 11 and give five s-extremal codes with d = 7. We construct four s-extremal codes of length n = 13 and minimum distance d = 5. We relate an s-extremal code of length 3d to another s-extremal code of that length, and produce extremal Type II codes from s-extremal codes
Two attacks on rank metric code-based schemes: RankSign and an IBE scheme
International audienceRankSign [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 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 [25] IBE scheme by the Hamming metric, then a devastating attack can be found
Wave: A New Family of Trapdoor One-Way Preimage Sampleable Functions Based on Codes
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 -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 by using and proving a variant of
the left-over hash lemma. We instantiate the new Wave-PSF family with ternary
generalized -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.Comment: arXiv admin note: text overlap with arXiv:1706.0806
Clinical Practice Guidelines for Childbearing Female Candidates for Bariatric Surgery, Pregnancy, and Post-partum Management After Bariatric Surgery
Emerging evidence suggests that bariatric surgery improves pregnancy outcomes of women with obesity by reducing the rates of gestational diabetes, pregnancy-induced hypertension, and macrosomia. However, it is associated with an increased risk of a small-for-gestational-age fetus and prematurity. Based on the work of a multidisciplinary task force, we propose clinical practice recommendations for pregnancy management following bariatric surgery. They are derived from a comprehensive review of the literature, existing guidelines, and expert opinion covering the preferred type of surgery for women of childbearing age, timing between surgery and pregnancy, contraception, systematic nutritional support and management of nutritional deficiencies, screening and management of gestational diabetes, weight gain during pregnancy, gastric banding management, surgical emergencies, obstetrical management, and specific care in the postpartum period and for newborns
Sources and Sinks of Greenhouse Gases from European Grasslands and Mitigation Options: The ‘GreenGrass’ Project
Adapting the management of grasslands may be used to enhance carbon sequestration into soil, but could also increase N2O and CH4 emissions. In support of the European post-Kyoto policy, the European \u27GreenGrass\u27 project (EC FP5, EVK2-CT2001-00105) has three main objectives: i) to reduce the large uncertainties concerning the estimates of CO2, N2O and CH4 fluxes to and from grassland plots under different climatic conditions and assess their global warming potential, ii) to measure net greenhouse gas (GHG) fluxes for different management which reflect potential mitigation options, iii) to construct a model of the controlling processes to quantify the net fluxes and to evaluate mitigation scenarios by up-scaling to a European level
Characterization of Multiple Ion Channels in Cultured Human Cardiac Fibroblasts
Background: Although fibroblast-to-myocyte electrical coupling is experimentally suggested, electrophysiology of cardiac fibroblasts is not as well established as contractile cardiac myocytes. The present study was therefore designed to characterize ion channels in cultured human cardiac fibroblasts. Methods and Findings: A whole-cell patch voltage clamp technique and RT-PCR were employed to determine ion channels expression and their molecular identities. We found that multiple ion channels were heterogeneously expressed in human cardiac fibroblasts. These include a big conductance Ca2+-activated K+ current (BKCa) in most (88%) human cardiac fibroblasts, a delayed rectifier K+ current (IKDR) and a transient outward K+ current (Ito) in a small population (15 and 14%, respectively) of cells, an inwardly-rectifying K+ current (IKir) in 24% of cells, and a chloride current (ICl) in 7% of cells under isotonic conditions. In addition, two types of voltage-gated Na+ currents (INa) with distinct properties were present in most (61%) human cardiac fibroblasts. One was a slowly inactivated current with a persistent component, sensitive to tetrodotoxin (TTX) inhibition (INa.TTX, IC50 = 7.8 nM), the other was a rapidly inactivated current, relatively resistant to TTX (INa.TTXR, IC50 = 1.8 μM). RT-PCR revealed the molecular identities (mRNAs) of these ion channels in human cardiac fibroblasts, including KCa.1.1 (responsible for BKCa), Kv1.5, Kv1.6 (responsible for IKDR), Kv4.2, Kv4.3 (responsible for Ito), Kir2.1, Kir2.3 (for IKir), Clnc3 (for ICl), NaV1.2, NaV1.3, NaV1.6, NaV1.7 (for INa.TTX), and NaV1.5 (for INa.TTXR). Conclusions: These results provide the first information that multiple ion channels are present in cultured human cardiac fibroblasts, and suggest the potential contribution of these ion channels to fibroblast-myocytes electrical coupling. © 2009 Li et al.published_or_final_versio
Atrial arrhythmogenicity in aged Scn5a+/∆KPQ mice modeling long QT type 3 syndrome and its relationship to Na+ channel expression and cardiac conduction
Recent studies have reported that human mutations in Nav1.5 predispose to early age onset atrial arrhythmia. The present experiments accordingly assess atrial arrhythmogenicity in aging Scn5a+/∆KPQ mice modeling long QT3 syndrome in relationship to cardiac Na+ channel, Nav1.5, expression. Atrial electrophysiological properties in isolated Langendorff-perfused hearts from 3- and 12-month-old wild type (WT), and Scn5a+/∆KPQ mice were assessed using programmed electrical stimulation and their Nav1.5 expression assessed by Western blot. Cardiac conduction properties were assessed electrocardiographically in intact anesthetized animals. Monophasic action potential recordings demonstrated increased atrial arrhythmogenicity specifically in aged Scn5a+/ΔKPQ hearts. These showed greater action potential duration/refractory period ratios but lower atrial Nav1.5 expression levels than aged WT mice. Atrial Nav1.5 levels were higher in young Scn5a+/ΔKPQ than young WT. These levels increased with age in WT but not Scn5a+/ΔKPQ. Both young and aged Scn5a+/ΔKPQ mice showed lower heart rates and longer PR intervals than their WT counterparts. Young Scn5a+/ΔKPQ mice showed longer QT and QTc intervals than young WT. Aged Scn5a+/ΔKPQ showed longer QRS durations than aged WT. PR intervals were prolonged and QT intervals were shortened in young relative to aged WT. In contrast, ECG parameters were similar between young and aged Scn5a+/ΔKPQ. Aged murine Scn5a+/ΔKPQ hearts thus exhibit an increased atrial arrhythmogenicity. The differing Nav1.5 expression and electrocardiographic indicators of slowed cardiac conduction between Scn5a+/ΔKPQ and WT, which show further variations associated with aging, may contribute toward atrial arrhythmia in aged Scn5a+/ΔKPQ hearts
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