TIDE:A novel approach to constructing timed-release encryption

In ESORICS 2021, Chvojka et al. introduced the idea of taking a time-lock puzzle and using its solution to generate the keys of a public key encryption (PKE) scheme [13]. They use this to define a timed- release encryption (TRE) scheme, in which the secret key is encrypted ‘to the future’ using a time-lock puzzle, whilst the public key is published. This allows multiple parties to encrypt a message to the public key of the PKE scheme. Then, once a solver has spent a prescribed length of time evaluating the time-lock puzzle, they obtain the secret key and hence can decrypt all of the messages. In this work we introduce TIDE (TIme Delayed Encryption), a novel approach to constructing timed-release encryption based upon the RSA cryptosystem, where instead of directly encrypting the secret key to the future, we utilise number-theoretic techniques to allow the solver to factor the RSA modulus, and hence derive the decryption key. We implement TIDE on a desktop PC and on Raspberry Pi devices validating that TIDE is both efficient and practically implementable. We provide evidence of practicality with an extensive implementation study detailing the source code and practical performance of TIDE

Investing in Risky Inputs in Senegal: Implications for Farm Profit and Food Production

While the productivity effects of the application of modern inputs, such as im- proved seeds or inorganic fertilizer, are well known, farmers in Sub-Saharan Africa tended to underinvest in purchased inputs. This underinvestment appears related to the unpredictable nature of agricultural production that is subject to risks and shocks. Farmers make production decisions before climatic and other shocks are realized. They, therefore, have no certainty about the outcome of their decisions. This makes investments in agricultural inputs very risky. This paper uses recent data for Senegal to identify the main drivers of the decision to purchase risky inputs (seeds and/or fertilizers), the level of investment and to quantify the impact of the use of risky inputs on household welfare. Using a Heck- man model, results show that the main drivers of the decision to purchase risky inputs include household composition, farmer organization, farm size, access to livestock income, and crop diversification. Drivers of the level of investment in risky inputs are gender, extension services, farm size, agricultural capital, and cropping patterns. Using an endogenous switching regression, we find a positive impact on the adoption of risky inputs on farm profit per hectare, and food available from production. The expected impact for non-adopters is found to be higher than that for adopters because they are involved in rice production (which is more responsive to inputs use) and in millet production (which is central for food security)

Détecteur temps réel de signaux cyclostationnaires. Principe et implémentation

L'impact des brouilleurs radioélectriques sur la qualité des observations de radiosources est un sujet de préoccupation croissante pour la communauté des radioastronomes. Dans le cadre des techniques de time-blanking, une méthode de détection en temps réel de brouilleurs cyclostationnaires est proposée. Elle repose sur la transformation d'un signal possédant une périodicité cachée en un signal périodique plus facilement détectable. Cet article expose la méthode propement dite, ainsi que les résultats de simulations obtenus avec des signaux de synthèse. Enfin, une implémentation électronique à partir d'un composant logique programmable est proposée

A statistical mixture method to reveal bottom-up and top-down factors guiding the eye-movements

When people gaze at real scenes, their visual attention is driven both by a set of bottom-up processes coming from the signal properties of the scene and also from top-down effects such as the task, the affective state, prior knowledge, or the semantic context. The context of this study is an assessment of manufactured objects (here car cab interior). From this dedicated context, this work describes a set of methods to analyze the eye-movements during the visual scene evaluation. But these methods can be adapted to more general contexts. We define a statistical model to explain the eye fixations measured experimentally by eye-tracking even when the ratio signal/noise is bad or lacking of raw data. One of the novelties of the approach is to use complementary experimental data obtained with the “Bubbles” paradigm. The proposed model is an additive mixture of several a priori spatial density distributions of factors guiding visual attention. The “Bubbles” paradigm is adapted here to reveal the semantic density distribution which represents here the cumulative effects of the top-down factors. Then, the contribution of each factor is compared depending on the product and on the task, in order to highlight the properties of the visual attention and the cognitive activity in each situation

Mineral Resources: Stocks, Flows, and Prospects

This chapter focuses on metals as they provide the clearest example of the challenges and opportunities that mineral resources present to society, in terms of both primary production and recycling. Basic concepts, information requirements and sources of consumer and industrial resource demand are described as well as the destabilizing effects of volatile resource prices and supply chain disruptions. Challenges facing extraction of in-ground resources and production of secondary resources are discussed and scenarios for the future considered. The results of the scenarios indicate that particularly energy and, as well, water and land requirements could become increasingly constraining factors for metal production. Key research questions are posed and modeling and data priorities discussed, with an emphasis on areas that require novel concepts and analytic tools to help lessen negative environmental impacts associated with minerals. The challenge of sustainability requires collaboration of practitioners and analysts with a multidisciplinary understanding of a broad set of issues, including economics, engineering, geology, ecology, and mathematical modeling, to name a few, as well as policy formulation and implementation.

Modèle de formation d'images gammagraphiques avec prise en compte de la dimension énergétique

- Cet article présente un modèle de processus de formation d'images applicable à l'imagerie médicale gammagraphique. Ce modèle physique prend en compte l'énergie des photons détectés après leur diffusion au sein du milieu environnant. Tout comme la dernière génération de caméras SPECT opérant en mode liste, il est capable de fournir un ensemble d'images indexées en énergie. Son temps de calcul, réduit, ouvre la voie au développement de nouvelles méthodes de restauration d'images utilisant la dimension énergétique. Une analyse en composantes principales (ACP) opérée sur la série d'images multiénergie fournit des résultats inattendus