Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Hardware security for post-quantum cryptography based on elliptic curve isogenies

DPACA (CTReg)

Autre

01-10-2019

SL-DRT-19-0626

simon.pontie@cea.fr

The main objective of this PhD thesis is to design protections to improve the security of SIKE (Supersingular Isogeny Key Encapsulation) implementations against side-channel and fault attacks. Walks in elliptic curve isogeny graphs can be used to establish a shared secret with a Diffie-Hellman protocol. SIKE is a key encapsulation suite based on this asymmetric cryptography. It is executed on conventional computer and is thought to be secure against an attack by a quantum computer. NIST has initiated a competitive "post-quantum" cryptography standardisation. These algorithms were built to avoid cryptanalysis. But, attackers may explore alternative attack methods that exploit physical access to implementation. Electromagnetic radiation analysis of deciphering or fault injection are examples of such attacks. There exist protections to hide secrets which used by implementations of classical cryptography. But, there are only few counter-measures to protect SIKE implementations and the threat of physical attacks against isogeny-based cryptography is not well known, up to now. This thesis will address these two problems. The PhD student will begin with studying SIKE protocol and existing implementations. He/She will have to identify existing physical attack propositions and to provide new attack methods. To refine the threat characterisation, he/she will build attack demonstrators based on side-channel analysis and/or fault injection. He/She will propose counter-measures that could be algorithmic, software or hardware methods to protect SIKE implementation. The SAS "Secure Architectures and Systems" research group is located close to Marseille (FRANCE). It is a joint CEA and EMSE team with state-of-art equipment to perform side-channel and fault attacks. PhD student supervisors are Nadia El-Mrabet (EMSE/SAS), Luca De Feo (UVSQ/CRYPTO) and Simon Pontié (CEA/SAS).

Propagation of elastic waves in embedded guides: Forward model and imaging with sampling method

Département Imagerie Simulation pour le Contrôle (LIST)

Laboratoire Méthodes CND

01-10-2019

SL-DRT-19-0627

arnaud.recoquillay@cea.fr

Additive manufacturing using ferrite powder for power electronics

Département des Technologies des NanoMatériaux (LITEN)

Laboratoire Matériaux Avancés et mise en forme

01-10-2019

SL-DRT-19-0630

ulrich.soupremanien@cea.fr

In just a few years, power electronics has become an essential technology that has spread throughout the world of electrical engineering. By 2030, nearly 80% of the electrical energy should pass through a stage controlled by power electronics. The current challenge of the developments is focused on increasing switching frequencies to improve converter efficiencies. Operating frequencies can now reach values above MHz and energy densities targeted will be 5 to 10 times larger than those of silicon-based components. Important issues exist since the analysis of a full converter shows that the non-optimized performance of passive components operating at very high switching velocities constitutes a so-called critical barrier. Significant efforts are required to develop passive magnetic components whose efficiency (low losses), high working switching frequency and sizing control (downscaling and thermal management) are optimized. Stereolithography (SLA) appears to be an interesting additive manufacturing technique to overcome the dimensional issues discussed here. This technology offers the possibility of designing complex parts. The main SLA bottleneck for ferrite concerns the interaction between "UV light and charged resin". Ferrite absorbs UV radiation and inhibits the photopolymerization reaction at high charge rate (>45%vol) that is the charge rate necessary to obtain a dense sintered material. A functionalization of the ferrite becomes necessary to obtain a crosslinkable resin.

field effect nanoionic synaptic transistors for neuromorphic applications

Département Composants Silicium (LETI)

Laboratoire Micro-Batteries Embarquées

01-09-2019

SL-DRT-19-0631

sami.oukassi@cea.fr

Neuromorphic computing represents an innovative technology that can perform intelligent and energy-efficient computation, whereas construction of neuromorphic systems requires biorealistic synaptic elements with rich dynamics that can be tuned based on a robust mechanism. As a result, there exists a tremendous upsurge of research interests on building neuromorphic systems, especially by exploiting the scalability and functionality of emerging devices (memristors, Reram). Recently, there is a growing interest on 3-terminal synaptic architectures (memtransistors), whose additional input terminal and modified device configuration have proven favorable for achieving complicated synaptic functions. Today, ion gated transistors appear as one of the most promising candidates, due to their low consumption, scalability and integration. They rely on the use of an ion conductor as a gate dielectric to drive or attract ions to/from the channel. Xxx. In this context, the objective of this PhD is to investigate novel solid-state nanoionic transistors as a synaptic device for neuromorphic applications. The main objective of the PhD is to investigate the potential synaptic behavior that can be achieved in field effect nanoionic transistors. To this aim various materials and device architectures will be characterized: channel with (i) ionic conductor or (ii) ionic conductor/host material bilayer. On these structures, synaptic behavior features will be quantified in terms of: linearity, symmetry, energy consumption etc?modelling could be used to analyze the physical effects taking place in the devices: ion drift and accumulation in the channel bulk or interfaces will be described and simulated. Based on the obtained results, a benchmark among the various tested technologies will be proposed. Then, the link between device stack (materials, thicknesses?) and synaptic capabilities will be clarified. The objective is to propose new device stacks (new elements, multilayers?) to optimize the device performances.

Epitaxial growth and nanosecond laser annealing of GeSn/SiGeSn heterostructures

Département Technologies Silicium (LETI)

Laboratoire

01-10-2019

SL-DRT-19-0635

Pablo.ACOSTAALBA@cea.fr

Since 2015, CEA LETI has the capacity of depositing GeSn/SiGeSn heterostructures on 200 mm substrates. We are currently at the state-of-the-art in several of their application domains. In ordre to fabricate electically-pumped lasers able to operate at room temperature and performant Infra-Red photodetectors, we will explore during this PhD thesis the n-type and p-type doping of such layers, be it by ion implantation or in-situ during the epitaxial growth itself. In order to take full advantage of those doped layers, we will perform recristallisation and electrical activation anneals. With standard annealing techniques, we would be faced with the significant instability of GeSn / SiGeSn stacks (tin precipitation / surface segregation). This is why we will evaluate, during this PhD thesis, the interest of using nanosecond laser anneals and their impact on the structural and electrical properties of those stacks. Those studies, which will be conducted in our brand new SCREEN-LASSE LT3100 tool, will be among the first ever conducted on this type of semiconductors. We will notably focus on the evolution of cristalline quality, doping level, surface roughness, tin agglomeration / segregation and chemical content with the various process parameters (epitaxy and laser anneals). Such a know-how will be put to good use for the fabrication of innovative optoelectronics devices.

Study and mitigation of ionomer degradation in PEMFC electrodes by combining electrochemistry and Operando Neutron/X-Ray characterizations

Département de l'Electricité et de l'Hydrogène pour les Transports (LITEN)

Laboratoire Analyse électrochimique et Post mortem

01-10-2019

SL-DRT-19-0638

sylvie.escribano@cea.fr

Despite huge improvements in the past decade, advances in the performance and durability of PEMFC are still necessary for them to compete with existing technologies. The proton conducting ionomer, contained in the electrodes of PEMFC, is conjectured to be one of the major causes in performance losses. Few studies have been carried out on this ionomer within the electrodes because of the difficulty in characterizing its distribution and properties. Thus, the degradation mechanisms of the ionomer during operation, highly dependent on water content, are still largely hypothetical but believed to lead to modifications of its distribution, chemical and physical structure, transport properties and its contamination by cations. In this PhD, we wish to elucidate the mechanisms by coupling electrochemical and microstructural characterizations with in-situ and operando experiments using Neutrons (ILL) and X-Ray probes (ESRF, SOLEIL), furthermore including accelerated aging tests to simultaneously correlate performance degradation and local modifications of the materials. Specifically, the structure of the ionomer will be investigated by SANS and the water content in the electrodes using neutron radiography. As a result of these investigations we also aim at improving durability of PEMFC by tuning the composition of the electrodes or proposing more appropriate operating strategies as two kinds of mitigation pathways which will be validated towards selected ageing protocols. Achieving these goals is essential for the widespread adoption of PEMFC in clean transportation systems.

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