Olivier Ly

Distance labeling in hyperbolic graphs

A graph G is δ-hyperbolic if for any four vertices u,v,x,y of G the two larger of the three distance sums dG(u,v) + dG(x,y), dG(u,x) + dG(v,y), dG(u,y) + dG(v,x) differ by at most δ, and the smallest δ ≥ 0 for which G is δ-hyperbolic is called the hyperbolicity of G. In this paper, we construct a distance labeling scheme for bounded hyperbolicity graphs, that is a vertex labeling such that the distance between any two vertices of G can be estimated from their labels, without any other source of information. More precisely, our scheme assigns labels of O(log2n) bits for bounded hyperbolicity graphs with n vertices such that distances can be approximated within an additive error of O(log n). The label length is optimal for every additive error up to ne. We also show a lower bound of Ω(log log n) on the approximation factor, namely every s-multiplicative approximate distance labeling scheme on bounded hyperbolicity graphs with polylogarithmic labels requires s = Ω(log log n).

The BINCOA framework for binary code analysis

This paper presents the BINCOA framework, whose goal is to ease the development of binary code analysers by providing an open formal model for low-level programs (typically: executable files), an XML format for easy exchange of models and some basic tool support. The BINCOA framework already comes with three different analysers, including simulation, test generation and Control-Flow Graph reconstruction.

Using Coq to verify Java card applet isolation properties

This paper reports on the use of the Coq proof assistant for the formal verification of applet isolation properties in Java Card technology. We focus on the confidentiality property. We show how this property is verified by the card manager and the APIs, extending our former proof addressing the Java Card virtual machine. We also show how our verification method allows to complete specifications and to enhance the secure design of the platform. For instance, we describe how the proof of the integrity puts the light on a known bug. Finally, we present the benefits of the use of high order modelling to handle the complexity of the system, to prove security properties and eventually to construct generic re-usable proof architectures.

Bio-inspired vertebral column, compliance and semi-passive dynamics in a lightweight humanoid robot

This paper presents the humanoid robot Acroban. We study two main issues: 1) Compliance and semi-passive dynamics for locomotion of humanoid robots regarding robustness against unknown external perturbations; 2) The advantages of a bio-inspired multi-articulated vertebral column. We combine mechatronic compliance with structural compliance due to the use of flexible materials. And we explore how these capabilities allow to enforce morphological computation in the design of robust dynamic locomotion. We also investigate the use of compliance to design semi-passive motor primitives using the torso and the arms as a system of accumulation/release of potential/kinetic energy.

Exploring robust, intuitive and emergent physical human-robot interaction with the humanoid robot Acroban

We present how a humanoid robot, called Acroban, allows whole-body robust, natural and intuitive physical interaction with both adults and children. These physical human-robot interaction are made possible through the combination of several properties of Acroban: 1) it is whole-body compliant thanks to variable impedance control and also thanks to the use of elastics and springs; 2) it has a bio-inspired vertebral column allowing more flexibility in postural and equilibrium control; 3) it is lightweight; 4) it has simple low-level controllers that leverage the first three properties. Moreover, the capabilities for physical human-robot interaction that we show are not using a model of the human, and in this sense are “model free”: 1) the capability of the robot to keep its equilibrium while being manipulated or pushed by humans is a result of the intrinsic capability of the whole body to absorb unpredicted external perturbations; 2) the capability of leading Acroban by the hand is an emergent human-robot interface made possible by the self-organizing properties of the body and its low-level controllers and was observed a posteriori only after the robot was conceived and without any initial plan to make this possible. Finally, an originality of Acroban is that is is made with relatively low-cost components which lack of precision is counterbalanced with the robustness due to global geometry and compliance.

Maturational constraints for motor learning in high-dimensions: The case of biped walking

This paper outlines a new developmental approach to motor learning in very high-dimensions, applied to learning biped locomotion in humanoid robots. This approach relies on the formal modeling and coupling of several advanced mechanisms inspired from human development for actively controlling the growth of complexity and harnessing the curse of dimensionality: 1) Maturational constraints for the progressive release of new degrees of freedoms and progressive increase their explorable ranges; 2) Motor synergies; 3) Morphological computation; 4) Social Guidance. An experimental setup involving a simulated version of the Acroban Humanoid robot is presented.

A Smart Card Power Analysis Simulator

Side-channel attacks are a great threat to cryptographicalgorithms embedded in microcontrollers. This paper proposesa software environment devoted to the analysisof resistance of cryptographic algorithms implementationsagainst differential power attacks. Our method consists ingenerating execution traces and computing abstractions ofthese traces at different levels, on the basis on classicalconsumption models. In particular this allows the user toisolate some parts of its implementation in order to analyzeinformation leakages directly linked to them. The advantageof this environment is twofold. Firstly, it produces preciseand differential analysis of a cryptographic algorithm resistanceto side-channel attacks. Secondly, it replaces the useof the testbed in the first development stages thus improvingthe global design process for resistant implementations bymaking easier interactions between development and validation.To other extends, the design of the simulator relieson a functional style, opening the way to formal proofs ofresistance.

Automated extraction of polymorphic virus signatures using abstract interpretation

In this paper, we present a novel approach for the detection and signature extraction for a subclass of polymorphic computer viruses. Our detection scheme offers 0 false negative and a very low false positives detection rate. We use context-free grammars as viral signatures, and design a process able to extract this signature from a single sample of a virus. Signature extraction is achieved through a light manual information gathering process, followed by an automatic static analysis of the binary code of the virus mutation engine.

Acroban the humanoid: playful and compliant physical child-robot interaction

Personal robotics is predicted to arrive massively in our homes in the 21st century, as well as impact importantly our society. Yet, before this vision can be realized, a number of very hard challenges need to be addressed. Among them are challenges related to human-robot interaction. Most personal robots, from entertainment to assistive robots, will need to interact with humans in a day-to-day basis: this implies that robot should afford intuitive, safe and pleasant interactions, as well as be able to adapt robustly to all unpredicted human behaviours. Many studies and technologies have elaborated in the field of human-robot interaction. In spite of this, physical human-robot interactions, which is central and unavoidable in real-world scenarios, have been only very little studied, in particular because existing hardware, humanoids in particular, did not allow easily for both safe and compliant interactions.

Metabot: A Low-Cost Legged Robotics Platform for Education

This paper introduces an open-source 3D printed low-cost legged robot environment designed for educational purposes. The platform, called Metabot, is already operational and is currently experienced by teachers and pupils. The robot as a teaching aid, has several advantages: at first, it is stimulating for pupils, especially legged robots. Second, robotics is multidisciplinary and centralizes a broad spectrum of knowledge for the pupils, in particular, it allows to introduce programming in a concrete environment, which is now an important need in school. Finally, legged robots can illustrate concretely several matters of geometry.