Marc Beunardeau

Fully Homomorphic Encryption: Computations with a Blindfold

To leverage the power of cloud computing, you can no longer encrypt data the traditional way. However, anyone (including the cloud service itself) can easily read unencrypted data. Fully homomorphic encryption reconciles this dilemma.

Cdoe Obofsucaitn: Securing Software from Within

A major cryptographic breakthrough in 2013 led to a candidate for a cryptographic construction: indistinguishability obfuscation.1 For the first time, a potential formal basis for code obfuscation was within reach. This sparked a spate of publications on the topic. However, despite the excitement, researchers encountered many technical challenges; for example, practical implementation of the proposed obfuscation was excruciatingly slow and not nearly as secure as hoped. But these papers generated a good starting point, community-wide excitement, and new determination motivated as much by overcoming scientific challenges as by the need for program obfuscation.

Uniform Sampling for Timed Automata with Application to Language Inclusion Measurement

Monte Carlo model checking introduced by Smolka and Grosu is an approach to analyse non-probabilistic models using sampling and draw conclusions with a given confidence interval by applying statistical inference. Though not exhaustive, the method enables verification of complex models, even in cases where the underlying problem is undecidable. In this paper we develop Monte Carlo model checking techniques to evaluate quantitative properties of timed languages. Our approach is based on uniform random sampling of behaviours, as opposed to isotropic sampling that chooses the next step uniformly at random. The uniformity is defined with respect to volume measure of timed languages previously studied by Asarin, Basset and Degorre. We improve over their work by employing a zone graph abstraction instead of the region graph abstraction and incorporating uniform sampling within a zone-based Monte Carlo model checking framework. We implement our algorithms using tools PRISM, SageMath and COSMOS, and demonstrate their usefulness on statistical language inclusion measurement in terms of volume.

White-Box Cryptography: Security in an Insecure Environment

Public cryptographic implementations work when the secret key is stored in a tightly secured environment. But what happens if adversaries penetrate that environment? Although many hardware countermeasures aim to keep adversaries at bay, white-box cryptography can provide yet another layer of protection at the software level.

Reusing Nonces in Schnorr Signatures

The provably secure Schnorr signature scheme is popular and efficient. However, each signature requires a fresh modular exponentiation, which is typically a costly operation. As the increased uptake in connected devices revives the interest in resource-constrained signature algorithms, we introduce a variant of Schnorr signatures that mutualises exponentiation efforts.

Honey Encryption for Language

Honey Encryption (HE), introduced by Juels and Ristenpart (Eurocrypt 2014, [12]), is an encryption paradigm designed to produce ciphertexts yielding plausible-looking but bogus plaintexts upon decryption with wrong keys. Thus brute-force attackers need to use additional information to determine whether they indeed found the correct key.

Failure is Also an Option

The Nijmeegse Vierdaagse http://www.4daagse.nl/en/ is the worlds most famous walking event. The walk is known to be challenging and each year about 10i¾ź% of the participants drop out. In 2016 the Vierdaagse will celebrate its centennial anniversary. In the walker community there is a frenzy about participating in the centennial walk. Initially, the rules governing participation were the following: A walker who succeeds the n-th walk is admitted to walk at year

From Clustering Supersequences to Entropy Minimizing Subsequences for Single and Double Deletions.

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