I'm Thomas Espitau - エスピト トマ- and I am a senior researcher at PQShield.
I pursued my Ph.D. in algorithmic number theory at Sorbonne University in Paris, advised by prof. Antoine Joux and prof. Pierre-Alain Fouque. I then joined the research labs of NTT in Tokyo, Japan.
I am an avid freeride skier and surfer. You can probably find me around 東浪 and 一宮's breaks during typhoons or in Hakuba valley or Hokkaido in winter.
We describe the 三鷹 signature scheme: a new hash-and-sign scheme over NTRU lattices which can be seen as a variant of NIST finalist FALCON. It achieves comparable efficiency but is considerably simpler, online/offline, and easier to parallelize and protect against side- channels, thus offering significant advantages from an implementation standpoint. It is also much more versatile in terms of parameter selection..
We present a general framework for polynomial-time lattice Gaussian sampling. It revolves around a systematic study of the discrete Gaussian measure and its samplers under extensions of lattices; we first show that given lattices Λ′ ⊂ Λ we can sample efficiently in Λ if we know how to do so in Λ′ and the quotient Λ/Λ′, regardless of the primitivity of Λ′. As a direct applications, we tackle the problem of domain extension and restriction for sampling and propose a sampler tailored for lattice filtrations, which can be seen as a broad generalization of the celebrated Klein’s sampler.
We exhibit a hierarchy of polynomial time algorithms solving approximate variants of the Closest Vector Problem. Our contributions is on the one hand a heuristic algorithm achieving the same distance as HSVP algorithms, and on the other hand a proven reduction from approximating the closest vector with a factor \(\approx n^{\frac32}\beta^{\frac{3n}{2\beta}}\) to the Shortest Vector Problem in dimension \(\beta\).
We introduce a framework for polynomial time reduction of lattices over number fields, leveraging their recursive and symplectic structures. Implementation page Talk at Simons Institute