Delegatable homomorphic encryption with applications to secure outsourcing of computation

In this work we propose a new cryptographic primitive called Delegatable Homomorphic Encryption (DHE). This allows a Trusted Authority to control/delegate the capability to evaluate circuits over encrypted data to untrusted workers/evaluators by issuing tokens. This primitive can be both seen as a public-key counterpart to Verifiable Computation, where input generation and output verification are performed by different entities, or as a generalisation of Fully Homomorphic Encryption enabling control over computations on encrypted data. Our primitive comes with a series of extra features as follows: 1) there is a one-time setup procedure for all circuits; 2) senders do not need to be aware of the functions which will be evaluated on the encrypted data, nor do they need to register keys; 3) tokens are independent of senders and receiver; and 4) receivers are able to verify the correctness of computation given short auxiliary information on the input data and the function, independently of the complexity of the computed circuit. We give a modular construction of such a DHE scheme from three components: Fully Homomorphic Encryption (FHE), Functional Encryption (FE), and a (customised) MAC. As a stepping stone, we first define Verifiable Functional Encryption (VFE), and then show how one can build a secure DHE scheme from a VFE and an FHE scheme. We also show how to build the required VFE from a standard FE together with a MAC scheme. All our results hold in the standard model.Finally, we show how one can build a verifiable computation (VC) scheme generically from a DHE. As a corollary, we get the first VC scheme which remains verifiable even if the attacker can observe verification result

Indium segregation and enrichment in coherent InxGa1-xAs/GaAs quantum dots

Significant differences in the image features of InxGa1-xAs quantum dots (QDs) grown on (001) and vicinal (001) GaAs were seen in [001] on-zone bright-held transmission electron microscope images. Simulated images were obtained by modeling the strain field distribution of the QDs with finite element analysis and then using this model in dynamical electron diffraction contrast simulations. Comparison of the experimental images and the simulated images shows that (i) In segregation exists in the QDs and (ii) the average In content of the QDs is higher than the average In content of the film

ELECTRICAL ACTIVITY OF Al DOPED SILICON ∑ 9 BICRYSTAL BY S.T.E.B.I.C.

The influence of aluminium on the electrical properties of silicon bicrystals was analyzed and related to the interaction between impurities and defects. A p-type silicon ∑ 9 symmetrical tilt bicrystal, with a chemical gradient in aluminium was grown by a directional solidification method. The combination of electrical, chemical and structural local information, with high spatial resolution enabled the electrical activity to be correlated to the cristallochemistry of the boundary. It was shown that the recombining activity depends on the localization and environment of aluminium

Development and pharmaceutical performance of a novel co-processed excipient of alginic acid and microcrystalline cellulose

International audienc

ELECTRICAL ACTIVITY OF GRAIN BOUNDARIES IN SILICON GROWN WITH AN ALUMINIUM CONTENT GRADIENT

In order to discriminate between the role of the structure and chemistry on the electrical activity of boundaries, p-type silicon bicrystals, characterized by a chemical gradient in aluminium from bottom to top of the ingot, were grown by a directional solidification method. The crystallographical and chemical analysis of symmetrical tilt boundaries namely Σ9, 13 and 25 was carried out by TEM and STEM X-ray spectroscopy. The electrical activity was studied by the scanning transmission electron beam induced current technique (STEBIC) which allowed the direct correlation with the microstructure to be achieved. It is shown that these coincidence tilt boundaries do not show intrinsic activity and that their behaviour is related to chemical decoration. The specific electrical activity of each type of decoration is considered.Afin de déterminer l'importance relative de la structure et de la chimie des joints sur leur activité électrique, nous avons élaboré par solidification directionnelle des bicristaux de silicium de type p dotés d'un gradient de composition en aluminium le long du lingot. La cristallochimie des joints symétriques de flexion Σ9, 13 et 25 a été étudiée par TEM et microanalyse STEM. L'activité électrique a été observée par la technique du courant induit sur lame mince, en microscopie électronique en transmission à balayage (STEBIC), qui permet la corrélation directe avec la microstructure. On montre que les joints symétriques de flexion ne présentent pas d'activité électrique intrinsèque et qu'ils ne sont recombinants que lorsqu'ils sont décorés. On décrit le comportement spécifique de chaque type de décoration

Femtosecond Dynamics of Light Transmission Through Sub-Wavelength Hole Arrays in Metallic Films

We report on the observation of an ultrafast modification of ~30% in the enhanced transmission through sub-wavelength nanometric apertures in metallic films. It demonstrates the feasibility of nanoscaled femtosecond optical switches