dr inż. Tomasz Michałek


Doktorat
2005-11-24Metoda oceny wiarygodności symulacji numerycznych przepływów lepkich i termicznych 
promotor -- prof. dr hab. Tomasz Kowalewski, IPPT PAN
716 
Ostatnie publikacje
1.Szczepański J., Amigó J.M., Michałek T., Kocarev L., Cryptographically secure substitutions based on the approximation of mixing maps, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS, ISSN: 1549-8328, DOI: 10.1109/TCSI.2004.841602, Vol.52, No.2, pp.443-453, 2005

Streszczenie:

In this paper, we explore, following Shannon’s suggestion that diffusion should be one of the ingredients of resistant block ciphers, the feasibility of designing cryptographically secure substitutions (think of S-boxes, say) via approximation of mixing maps by periodic transformations. The expectation behind this approach is, of course, that the nice diffusion properties of such maps will be inherited by their approximations, at least if the convergence rate is appropriate and the associated partitions are sufficiently fine. Our results show that this is indeed the case and that, in principle, block ciphers with close-to-optimal immunity to linear and differential cryptanalysis (as measured by the linear and differential approximation probabilities) can be designed along these guidelines. We provide also practical examples and numerical evidence for this approximation philosophy.

Słowa kluczowe:

Black cipher, differential cryptanalysis, linear cryptanalysis, mixing dynamical system, periodic approximation, S box

Afiliacje autorów:

Szczepański J.-IPPT PAN
Amigó J.M.-Universidad Miguel Hernández-CSIC (ES)
Michałek T.-IPPT PAN
Kocarev L.-University “Kiril i Metodij”, Skopje (MK)
2.Michałek T., Kowalewski T.A., Šarler B., Natural convection for anomalous density variation of water - numerical benchmark, PROGRESS IN COMPUTATIONAL FLUID DYNAMICS, ISSN: 1468-4349, DOI: 10.1504/PCFD.2005.006751, Vol.5, pp.158-170, 2005

Streszczenie:

A steady-state natural convection in a differentially heated cavity for temperatures in a vicinity of the freezing point is used to investigate and compare performance of four different numerical methods: finite differences, finite volume, finite elements and mesh-free diffuse approximation method. A primary aim of the exercise is to define a new numerical benchmark solution for natural convection problems, which includes challenging configuration of strongly non-linear buoyancy term. This configuration is used to test the performance of two popular commercial codes (Fluent and Fidap) and to compare them with two classical finite difference codes and the new promising mesh-free implementation.

Słowa kluczowe:

numerical simulation, numerical benchmarks, mesh-free methods, natural convection

Afiliacje autorów:

Michałek T.-IPPT PAN
Kowalewski T.A.-IPPT PAN
Šarler B.-University of Nova Gorica (SI)