Matematiikan ja systeemianalyysin laitos

Ajankohtaista

Esitelmiä, seminaareja ja väitöksiä

* Seuraavan viikon tapahtumat merkitty tähdellä

Ivy Woo
Partial Lattice Trapdoors: How to Split Lattice Trapdoors, Literally
* Today * Monday 22 April 2024,   13:30,   Väre Q203
We introduce a natural technique for sharing lattice trapdoors: splitting them into partial trapdoors of smaller dimensions. We define security properties for these objects and prove these properties for a simple construction. Our proofs are based on the k-MSIS and k-MLWE assumptions together with the following conjecture: sampling two matrices with entries following discrete Gaussian distributions of width \sigma_0 or \sigma_1 and then sampling a matrix with entries following a discrete Gaussian distribution of width \sigma > \poly \cdot \max(\sigma_0, \sigma_1) from the lattices spanned by these two matrices leads to two distributions that are statistically close. We construct simple threshold signatures and IBE schemes from this primitive to illustrate its utility.
Cryptography seminar

Gerald Williams (University of Essex)
Incidence graphs of generalized polygons and star graphs of group presentations with cyclic symmetry
* Today * Monday 22 April 2024,   16:15,   M3 (M234)
A generalized polygon is a point-line incidence structure that includes projective planes (generalized 3-gons). Incidence graphs of generalized m-gons are connected bipartite graphs of diameter m and girth 2m. Associated to any group presentation is a graph called the star graph, which encodes structural information about the group defined by the presentation. Transitional behaviour can occur for groups defined by presentations whose star graph components are incidence graphs of generalized polygons; such presentations are called “special”. A cyclic presentation of a group is a type of group presentation that admits a cyclic symmetry. In this talk I will discuss joint work with Ihechukwu Chinyere in which we classify the special cyclic presentations.
Algebra and discrete mathematics seminar

Anna-Mariya Otsetova
Axisymmetric capillary water waves with vorticity and swirl connecting to static unduloid configurations
* Wednesday 24 April 2024,   10:15,   M3 (M234)
We study steady axisymmetric water waves with general vorticity and swirl, subject to the influence of surface tension. Explicit solutions to such a water wave problem are static configurations where the surface is an unduloid, that is, a periodic surface of revolution with constant mean curvature. We prove that to any such configuration there connects a global continuum of non-static solutions by means of a global implicit function theorem and topological degree theory. To prove this, the key is strict monotonicity of a certain function describing the mean curvature of an unduloid and involving complete elliptic integrals. From this point of view, this paper is an interesting interplay between water waves, geometry, and properties of elliptic integrals. This is a joint work with Jörg Weber (University of Vienna) and Erik Wahlén (Lund University).
Seminar on analysis and geometry

Leevi Kaukonen
MSc thesis presentation
* Wednesday 24 April 2024,   14:15,   M3 (M234)
Diplomityöesitelmä
Diplomityöesitelmä / Hakula

Lauri Nyman
Distance to singularity for matrix pencils via Riemannian optimization
* Thursday 25 April 2024,   09:15,   M2 (M233)

Joonas Laaksonen
MSc thesis presentation
Monday 29 April 2024,   14:15,   M3 (M234)
Diplomityöesitelmä
Diplomityöesitelmä / Hakula

Oula Kekäläinen
MSc thesis presentation
Monday 29 April 2024,   16:15,   M3 (M234)
Algebra and discrete mathematics seminar

Rodrigo Martín Sánchez-Ledesma (Complutense U. Madrid / INDRA)
Overview and extension of root-based attacks against PLWE instances
Tuesday 07 May 2024,   15:15,   M2 (M233)
The Polynomial Learning With Errors problem (PLWE) serves as the background of two of the four cryptosystems standardised in July 2022 by the National Institute of Standards and Technology to replace non-quantum resistant current primitives like those based on RSA, finite field based Diffie-Hellman and its elliptic curve analogue. Although PLWE is highly believed to be quantum resistant, unlike other post-quantum proposals like multivariate and some code based ones, this fact has not yet been established. Moreover, several vulnerabilities have been encountered for a number of specific instances. In a search for more flexibility, it becomes fully relevant to study the robustness of PLWE based on other polynomials, not necessarily cyclotomic. In 2015, Lauter et al. found a good number of attacks based on different features of the roots of the polynomial. In the present talk we present an overview of the approximations made against PLWE derived from these work, along with several new attacks which refine those by Lauter exploiting the order of the trace of roots over finite extensions of the finite field under the three scenarios laid out by Lauter et al, allowing to generalize the setting in which the attacks can be carried out. This is joint work with I. Blanco-Chacón and R. Durán.
ANTA Seminar / Hollanti et al.

Dr. Benjamin Jany (TU Eindhoven)
TBA
Monday 13 May 2024,   14:15,   M2 (M233)
ANTA Seminar / Hollanti et al.

Lilja Metsälampi
Midterm review
Monday 13 May 2024,   16:15,   M3 (M234)
Algebra and discrete mathematics seminar

Lauri Särkiö
TBA/Midterm review
Wednesday 15 May 2024,   11:15,   M3 (M234)

Kai Hippi
TBA
Wednesday 15 May 2024,   14:15,   M3 (M234)
Seminar on analysis and geometry

Sari Rogovin
Linear dilatation and absolute continuity
Thursday 16 May 2024,   10:15,   M3 (M234)
Seminar on analysis and geometry

Patricija Sapokaitė
Midterm review
Monday 27 May 2024,   11:15,   M3 (M234)
Algebra and discrete mathematics seminar

Prof. Sueli I. R. Costa (Unicamp, Brazil)
TBA
Monday 03 June 2024,   13:15,   M2 (M233)
ANTA Seminar / Hollanti et al.

Okko Makkonen
Midterm review: TBA
Thursday 13 June 2024,   11:15,   M3 (M234)
ANTA Seminar / Hollanti et al.

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