A Mathematical Problem for Security Analysis of Hash Functions and Pseudorandom Generators

In this paper, we specify a class of mathematical problems, which we refer to as "Function Density Problems" (FDPs, in short), and point out novel connections of FDPs to the following two cryptographic topics; theoretical security evaluations of keyless hash functions (such as SHA-1.), and constructions of provably secure pseudorandom generators (PRGs) with some enhanced security property introduced by Dubrov and Ishai (STOC 2006). Our argument aims at proposing new theoretical frameworks for these topics (especially for the former) based on FDPs, rather than providing some concrete and practical results on the topics. We also give some examples of mathematical discussions on FDFs, which would be of independent interest from mathematical viewpoints. Finally, we discuss possible directions of future research on other cryptographic applications of FDPs and on mathematical studies on FDPs themselves.ArticleINTERNATIONAL JOURNAL OF FOUNDATIONS OF COMPUTER SCIENCE. 26(2):169-194 (2015)journal articl

An Edge-Signed Generalization of Chordal Graphs, Free Multiplicities on Braid Arrangements, and Their Characterizations

In this article, we propose a generalization of the notion of chordal graphs to signed graphs, which is based on the existence of a perfect elimination ordering for a chordal graph. We give a special kind of filtrations of the generalized chordal graphs, and show a characterization of those graphs. Moreover, we also describe a relation between signed graphs and a certain class of multiarrangements of hyperplanes, and show a characterization of free multiarrangements in that class in terms of the generalized chordal graphs, which generalizes a well-known result by Stanley on free hyperplane arrangements. Finally, we give a remark on a relation of our results with a recent conjecture by Athanasiadis on freeness characterization for another class of hyperplane arrangements

Measurement of the mechanical loss of a cooled reflective coating for gravitational wave detection

We have measured the mechanical loss of a dielectric multilayer reflective coating (ion-beam sputtered SiO$_2$ and Ta$_2$O$_5$) in cooled mirrors. The loss was nearly independent of the temperature (4 K $\sim$ 300 K), frequency, optical loss, and stress caused by the coating, and the details of the manufacturing processes. The loss angle was $(4 \sim 6) \times 10^{-4}$. The temperature independence of this loss implies that the amplitude of the coating thermal noise, which is a severe limit in any precise measurement, is proportional to the square root of the temperature. Sapphire mirrors at 20 K satisfy the requirement concerning the thermal noise of even future interferometric gravitational wave detector projects on the ground, for example, LCGT.Comment: 8 pages, 6 figures, 3 tables : accepted version (by Physical Review D

Qualitative Simulation for Early-Stage Service Design

Currently, the importance of services is widely accepted in various industries. Given this background, fundamental research on service engineering is carried out quite actively. Service engineering seeks to provide design methodology for services from an engineering perspective. In product and service design, designers are generally forced to spend a lot of redesign works if design changes occur at a late stage of the design process. Thus, it is important for designers to validate design solutions in the early stage(s) of the design process by using simulation methods. However, simulation models in the existing methods are built with quantitative information. In the early stages of the service design process, most of the information about a design solution is still not defined; therefore, it is difficult to obtain sufficient quantitative information. For obtaining such quantitative information, service providers need to offer a designed service to their customers as a trial, which impose much effort for building quantitative simulation models. In order to reduce such risks, this research applies a qualitative simulation method, which can be used to analyze the behavior of systems with fuzzy qualitative information. In this paper, we propose a method to build a qualitative simulation model with the design information available at the early stage(s) of the service design process. This method would enable designers to evaluate a design solution in the early stage of a service design process and would increases quality of the service design.サービス学会主催 The 3rd International Conference on Serviceology (ICServ 2015) July 7-9, 2015 in San Jose, CA, USA

Highly parallel SNP genotyping reveals high-resolution landscape of mono-allelic Ube3a expression associated with locus-wide antisense transcription

We investigated the allele- and strand-specific transcriptional landscape of a megabase-wide genomic region of mouse Ube3a (ubiquitin protein ligase E3A) by means of a highly parallel SNP genotyping platform. We have successfully identified maternal-specific expression of Ube3a and its antisense counterpart (Ube3a-ATS) in brain, but not in liver. Because of the use of inter-subspecies hybrid mice, this megabase-wide analysis provided high-resolution picture of the transcriptional patterns of this region. First, we showed that brain-specific maternal expression of Ube3a is restricted to the second half part of the locus, but is absent from the first half part. Balance of allelic expression is altered in the middle of the locus. Second, we showed that expression of the brain-specific Ube3a-ATS appeared to be terminated in the region upstream to the Ube3a transcription start site. The present study highlights the importance of locus-wide competition between sense and antisense transcripts

The Japanese space gravitational wave antenna; DECIGO

DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational wave antenna. DECIGO is expected to open a new window of observation for gravitational wave astronomy especially between 0.1 Hz and 10 Hz, revealing various mysteries of the universe such as dark energy, formation mechanism of supermassive black holes, and inflation of the universe. The pre-conceptual design of DECIGO consists of three drag-free spacecraft, whose relative displacements are measured by a differential Fabry– Perot Michelson interferometer. We plan to launch two missions, DECIGO pathfinder and pre- DECIGO first and finally DECIGO in 2024

DECIGO pathfinder

DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) which is a future space gravitational wave antenna. DECIGO is expected to provide us fruitful insights into the universe, in particular about dark energy, a formation mechanism of supermassive black holes, and the inflation of the universe. Since DECIGO will be an extremely large mission which will formed by three drag-free spacecraft with 1000m separation, it is significant to gain the technical feasibility of DECIGO before its planned launch in 2024. Thus, we are planning to launch two milestone missions: DPF and pre-DECIGO. The conceptual design and current status of the first milestone mission, DPF, are reviewed in this article

Coincidence analysis to search for inspiraling compact binaries using TAMA300 and LISM data

Japanese laser interferometric gravitational wave detectors, TAMA300 and LISM, performed a coincident observation during 2001. We perform a coincidence analysis to search for inspiraling compact binaries. The length of data used for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors are operated simultaneously. TAMA300 and LISM data are analyzed by matched filtering, and candidates for gravitational wave events are obtained. If there is a true gravitational wave signal, it should appear in both data of detectors with consistent waveforms characterized by masses of stars, amplitude of the signal, the coalescence time and so on. We introduce a set of coincidence conditions of the parameters, and search for coincident events. This procedure reduces the number of fake events considerably, by a factor $\sim 10^{-4}$ compared with the number of fake events in single detector analysis. We find that the number of events after imposing the coincidence conditions is consistent with the number of accidental coincidences produced purely by noise. We thus find no evidence of gravitational wave signals. We obtain an upper limit of 0.046 /hours (CL $= 90$) to the Galactic event rate within 1kpc from the Earth. The method used in this paper can be applied straightforwardly to the case of coincidence observations with more than two detectors with arbitrary arm directions.Comment: 28 pages, 17 figures, Replaced with the version to be published in Physical Review