Harvey: A Greybox Fuzzer for Smart Contracts

We present Harvey, an industrial greybox fuzzer for smart contracts, which are programs managing accounts on a blockchain. Greybox fuzzing is a lightweight test-generation approach that effectively detects bugs and security vulnerabilities. However, greybox fuzzers randomly mutate program inputs to exercise new paths; this makes it challenging to cover code that is guarded by narrow checks, which are satisfied by no more than a few input values. Moreover, most real-world smart contracts transition through many different states during their lifetime, e.g., for every bid in an auction. To explore these states and thereby detect deep vulnerabilities, a greybox fuzzer would need to generate sequences of contract transactions, e.g., by creating bids from multiple users, while at the same time keeping the search space and test suite tractable. In this experience paper, we explain how Harvey alleviates both challenges with two key fuzzing techniques and distill the main lessons learned. First, Harvey extends standard greybox fuzzing with a method for predicting new inputs that are more likely to cover new paths or reveal vulnerabilities in smart contracts. Second, it fuzzes transaction sequences in a targeted and demand-driven way. We have evaluated our approach on 27 real-world contracts. Our experiments show that the underlying techniques significantly increase Harvey's effectiveness in achieving high coverage and detecting vulnerabilities, in most cases orders-of-magnitude faster; they also reveal new insights about contract code.Comment: arXiv admin note: substantial text overlap with arXiv:1807.0787

Modélisation numérique multiphysiques couplés - Application à un projectile supersonique

The constant search for improved modeling complex multi-physics is now a key issue and be able to propose such an approach is a necessity in both a need for detailed analysis and performance improvement systems and studied. For example, suggest new generation missile systems force us to control both external aerodynamics and heat transfer associated while incorporating flight dynamics and possible changes in geometry associated with heat stress. Tackle such a coupled system is the primary motivation of this work. However, solving systems strongly coupled if necessary to propose a strategy in the modeling approach. The technique has been immersed boundaries retained and integrated into a compressible solver based on an automatic mesh generator structure 2nTree. Before even addressing the ablation mechanisms, work is particularly focused on the characterization of external flows around projectiles, academic initially to quickly converge SOCBT projectiles and ammunition arrows flying very high speeds. Quality results and excellent correlation with literature results have encouraged us to continue the development by coupling with a flight dynamics model of 6 ° of freedom and taking into account the heating of the projectile to take account in flight conditions (in particular the stability of the projectile). Heat flow may also cause thermal degradation and the proposed model allows taking into account phenomena ablation. Although the modeling is simplistic at first, the proposed model was able to describe fairly easy problem to moving boundary as a mechanism of ablation. Calculations have highlighted the interesting behavior of the numerical model on academic cases and fins features a round arrow. Calculation coupled fluid mechanics / heat projectile / ablation demonstrates the potential of the proposed model as well.La recherche constante de l'amélioration des modélisations complexes multi-physiques est aujourd'hui un enjeu primordial et être capable de proposer de telles approches devient une nécessité à la fois dans un besoin d'analyse fine et d'amélioration des performances des systèmes ainsi étudiés. Par exemple, proposer des systèmes balistiques de nouvelle génération nous force à maîtriser à la fois l'aérodynamique externe et ses transferts thermiques associés tout en y intégrant la dynamique du vol et les possibles modifications de la géométrie liés aux agressions thermiques. S'attaquer à un tel système couplé constitue la motivation première de ce travail. Cependant, résoudre des systèmes si fortement couplés impose de proposer une véritable stratégie dans la modélisation retenue. La technique des frontières immergées a été retenue et intégrée à un solveur compressible s'appuyant sur un générateur de maillage automatique structure en 2nTree. Avant même de s'attaquer aux mécanismes d'ablation, le travail s'est plus particulièrement focalisé sur la caractérisation d'écoulements externes autour de projectiles, académique dans un premier temps pour très vite converger vers des projectiles SOCBT et des munitions flèches volant à très grandes vitesses. La qualité des résultats obtenus et les excellentes corrélations avec les résultats de la littérature nous ont encouragé à poursuivre le développement par un couplage avec un modèle de dynamique du vol à 6° de liberté et la prise en compte de l'échauffement du projectile pour tenir compte des conditions en vol (notamment la stabilité du projectile). Les flux thermiques peuvent également engendrer des dégradations thermiques et le modèle proposé permet la prise en compte des phénomènes d'ablation. Bien que sa modélisation soit simpliste dans un premier temps, le modèle proposé a permis de décrire de manière assez facile un problème à frontière mobile comme l'est un mécanisme d'ablation. Les calculs ont soulignés le comportement intéressant du modèle numérique sur des cas académiques et sur des ailettes caractéristiques d'une munition flèche. Un calcul couplé mécanique des fluides/thermique du projectile/ ablation témoigne du fort potentiel du modèle ainsi proposé

Modélisation numérique multiphysiques couplés (application à un projectile en écoulement supersonique)

POITIERS-ENS Mécanique Aérot (860622301) / SudocSudocFranceF

Development of Antibacterial, Antioxidant, and UV-Barrier Chitosan Film Incorporated with Piper betle Linn Oil as Active Biodegradable Packaging Material

This study aims to introduce the antibacterial and antioxidant activities of the Piper betle Linn oil (PBLO) into chitosan film (pCS), named as pCS-PBLO film. The morphology, structure, and properties of the pCS-PBLO film, along with the PBLO concentration between 0.4% and 1.2% (v/v), were determined. The film surface became rough and heterogeneous with the addition of PBLO, which directly influenced on mechanical strength of the resultant film. The addition of the PBLO did not affect thermal stability but significant effect on flexibility and mobility of the film. Importantly, the film enhanced the UV-protective property and antioxidant activity as incorporated-PBLO. Moreover, the resulting film revealed the great inhibition efficiency against the negative-gram (E. coli, P. aeruginosa, and S. typhi) and positive-gram (S. aureus) bacteria based on phenolic compounds, such as the acetyleugenol, eugenol, 4-allyl-1,2-diacetoxybenzen, and chavicol acetate in PBLO components. In particular, the pCS-PBLO film may extend the shelf life of king oranges up to two weeks at 25 °C that is longer as compared to the uncoated sample and coated with chitosan alone. These results suggest that the pCS-PBLO film can be used as environmental-friendly and effective food packaging material in the future

Factors associated with successful publication for systematic review protocol registration: an analysis of 397 registered protocols

Abstract Background Meta-analyses are on top of the evidence-based medicine pyramid, yet many of them are not completed after they are begun. Many factors impacting the publication of meta-analysis works have been discussed, and their association with publication likelihood has been investigated. These factors include the type of systematic review, journal metrics, h-index of the corresponding author, country of the corresponding author, funding sources, and duration of publication. In our current review, we aim to investigate these various factors and their impact on the likelihood of publication. A comprehensive review of 397 registered protocols retrieved from five databases was performed to investigate the different factors that might affect the likelihood of publication. These factors include the type of systematic review, journal metrics, h-index of the corresponding author, country of the corresponding author, funding sources, and duration of publication. Results We found that corresponding authors in developed countries and English-speaking countries had higher likelihoods of publication: 206/320 (p = 0.018) and 158/236 (p = 0.006), respectively. Factors affecting publications are the countries of corresponding author (p = 0.033), whether they are from developed countries (OR: 1.9, 95% CI: 1.2–3.1, p = 0.016), from English-speaking countries (OR: 1.8, 95% CI: 1.2–2.7, p = 0.005), update status of the protocol (OR: 1.6, 95% CI: 1.0–2.6, p = 0.033), and external funding (OR: 1.7, 95% CI: 1.1–2.7, p = 0.025). Multivariable regression retains three variables as significant predictors for the publication of a systematic review: whether it is the corresponding author from developed countries (p = 0.013), update status of the protocol (p = 0.014), and external funding (p = 0.047). Conclusion Being on top of the evidence hierarchy, systematic review and meta-analysis are the keys to informed clinical decision-making. Updating protocol status and external funding are significant influences on their publications. More attentions should be paid to the methodological quality of this type of publication

Promoted Hydrogen Peroxide Production from Pure Water on g-C3N4 with Nitrogen Defects Constructed through Solvent-Precursor Interactions: Exploring A Complex Story in Piezo-Photocatalysis

Hydrogen peroxide (H2O2) production via oxygen (O2) reduction reaction (ORR) in pure water (H2O) through graphitic carbon nitrides (g-C3N4)-based piezo-photocatalysts is an exciting approach in many current studies. However, the low Lewis-acid properties of g-C3N4 limited the catalytic performance because of the low O2 adsorption efficacy. To overcome this challenge, we utilized the interaction of g-C3N4 precursors with various solvents to synthesize g-C3N4, possessing multiple nitrogen-vacant species via thermal shocking polymerization. Our results suggest that the lack of nitrogen in g-C3N4 and the incident introduction of oxygen-functional groups enhance the Lewis acid-base interactions and polarize the g-C3N4 lattices, leading to the enormous enhancement, roughly 7 times from the optimal samples compared to pristine g-C3N4 in pure water via piezo-photocatalysis. Meanwhile, we also observed the correlation between the charge separation kinetic and the crystalline degree of the synthesized materials, which can elucidate how the nitrogen defects impacted the catalytic outcomes. Furthermore, the catalytic mechanisms were thoroughly studied, with the formation of H2O2 proceeding via radical and water oxidation pathways, in which the roles of light and ultrasound were carefully investigated. Thus, our findings not only reinforce the potential view of metal-free photocatalysts, accelerating the understanding of g-C3N4 working principles to generate H2O2 based on the oxygen reduction and water oxidation reactions, but also propose a facile one-step way for fabricating highly efficient and scalable photocatalysts to produce H2O2 without using sacrificial agents, pushing the practical application of in-situ solar H2O2 toward real-world scenarios