OGAWA, Mizuhito Professor
School of Information Science, Intelligent Robotics Area, Research Centre for Interpretable AI, Research Center for Theoretical Computer Science
Ph.D from University Tokyo(2002) 東京大学
◆Professional Experience
: Japan Advanced Institute of Science and Technology (Research Professor, 2003-2007), Japan Advanced Institute of Science and Technology (Professor, 2007-), NII (Visiting Professor, 2008-)
: NTT Electoric Communication Laboratories (researcher, 1985-2001), Japan Science and Technology Corporation (researcher, 2002-2003)
◆Research Keywords
ソフトウェア検証, プログラム解析
◆Research Interests
Context-sensitive analyses for Large-scale Java programs
The aim of the research is to design and implement various contex-sensitive analyses of large-scale Java programs (say, 10000 methods) based on weighted pushdown model checking. The main focus is a context-sensitive and flow insensitive points-to analysis, and we proposed a new algorithm based on weighted pushdown model checking. Its implementation is ongoing with SOOT (translation to an intermediate language Jimple) as a frontend anf Weighted PDS library as a backend analysis engine.
Confluence of non-left-linear term rewriting systems
Confluence ans termination are basic properties of term rewriting systems (TRSs). When termination holds, Knuth and Bendix showed in 1970s that local confluence of critical pairs is enough for confluence. For nonterminationg TRSs, Rosen showed the orthogonality (i.e., left-linear and nonoverlapping) implies confluence in 1960's and Huet extended it to left-linear and prallel closed TRSs in 1980. For non-left-linear and non-terminating TRSs, Chew showed the unique normal form for strongly nonoverlapping TRSs. Toyama and Oyamaguchi conjectured that strongly nonoverlapping and right-linear TRSs are confluent in 1990, which is still an open problem. Many attempts based on decreasing diagrams failed so far, and we are tackling with a new proof techniques, called reduction graphs. Our current resutl is, a strongly nonoverlapping and weakly shallow TRS is confluent
Binary code analyzer BE-PUM for malware
Program analysis consists of two steps: model generation and model checking. For high level programming languages, such as C, Java, mthe former is straight forward by generating a contol flow graph (CFG). However, binary code, especially malware, it is not easy, since it does not distinguish code and data, and there are lots of obfuscation techniques, e.g., self modification and indirect jump. With the collaboration with VNU-HCMC, we have developped a model generater BE-PUM based on dynamic symbolic execution in an on-the-fly manner. It also works as a robust disassebler, and even as a general unpacker for packed code by many packers.
Well-structured pushdown systems
Decidability of infinite state transition systems has been explored in two directions: a well-structured transition system (WSTS), e.g., petri net, proposed by Finkl, et.al. on 1987, and a pushdown system, which has a stack. The key is a well-quasi ordering equiped for inifnite states. A well-structured pushdown system (WSPDS) combines both still keeping decidability. We showed the decidablity of the coverability if a WSTS has finite control states (and well-quasi-ordered stack alphabet), by using P-automata techniques, which reduced the coverability of a WSPDS into that of a WSTS (P-automaton). Our techniques cover many existing decidability resutls, e.g., braching VAS, recursive VASS, alternating VASS, multiset PDS. We also applied to variations of timed pushdown systems, nested timed automata (NeTA) with frozen clocks. A NeTA has finitely many timed automata as its control states and its stack alphabet. We showed the decidability of its reachability if it has at most one global clock.
raSAT: SMT solver for nonlinear constraints
An SMT solver solves the satisfiability of quantifier-free constraints. It has many variations of backend theory, e.g. linear arithmetic, uninterpreted function symbols, arrays. They are quite established theories, but non-linear artihmetic (polynomials) are still under investigation. The ultimate method is based on computer algebra, however, it does not scale. We take an alternative apractical approach based on interval arithmetic and the intermediate value theorem. Our idea is implemented as the tool raSAT, which has participated the internation SMT solver competition SMT-COMP 2015. It obtained 3rd among 6 tools in QFNRA category (nonlinear constraint over reals) and 2nd among 7 tools in QFNIA category (nonlinear constraint over integers).


◆Published Papers
On Classes of Regular Languages Related to Monotone WQOs.
Mizuhito Ogawa, Victor, L. Selivanov
Descriptional Complexity of Formal Systems - 21st IFIP WG 1.02 International Conference, DCFS 2019, Košice, Slovakia, July 17-19, 2019, Proceedings, 235-247, 2019
Comparison of Three Deep Learning-based Approaches for IoT Malware Detection.
Khanh Duy Tung, Nguyen, Tran Minh Tuan, Son Hai Le, Viet-Anh Phan, Mizuhito Ogawa, Nguyen Le Minh
10th International Conference on Knowledge and Systems Engineering, KSE 2018, Ho Chi Minh City, Vietnam, November 1-3, 2018, 382-388, 2018
Packer identification based on metadata signature
Nguyen Minh Hai, Mizuhito Ogawa, Quan Thanh Tho
ACM International Conference Proceeding Series, -, 2017
raSAT: an SMT solver for polynomial constraints
Vu Xuan Tung, To Van Khanh, Mizuhito Ogawa
Subtropical satisfiability
Pascal Fontaine, Mizuhito Ogawa, Thomas Sturm, Xuan Tung Vu
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 10483, 189-206, 2017
Generation of Program Analyzer Based on Model Checking
情報処理学会論文誌プログラミング(PRO), 44, 13, 25-37, 2003
◆Conference Activities & Talks
raSAT: SMT for Polynomial Inequality
12th International Workshop on Satisfiability Modulo Theories (SMT2014), TU Wien, Wien Austria, 2014
Non-E-overlapping and weakly shallow TRSs are confluent (Extended abstract)
IWC 2014 (3rd International Workshop on Confluence, TU Wien, Wien Austria, 2014

■Teaching Experience

Formal Languages and Automata(E), Mathematical Logic, Graphs and Automata, Algebra for Computer Scientist, 形式言語とオートマトン(E), 数理論理学, グラフとオートマトン理論, 情報代数

■Contributions to  Society

◆Academic Society Affiliations
Association for Computing Machinary, IPSJ, JSSST
◆Academic Contribution
10th IEEE RIVF International Conference on Computing and Communication Technologies (RIVF-2013) , Thanh-Thuy Nguyen・教授(副学長)・VNU-UET, Vietnam、小川瑞史・教授・JAIST, Japan (PC co-chairs) , 2013 - 2013 , Hanoi, Vietnam http://uet.vnu.edu.vn/rivf2013/
11th International Symposium on Automated Technology for Verification and Analysis (ATVA 2013) , Hung Dang-Van・教授・UET-VNU Hanoi, Vietnam、小川瑞史・教授・JAIST, Japan (PC co-chairs) , 2013 - 2013 , Hanoi, Vietnam http://www.uet.vnu.edu.vn/atva2013/index.htmlProceedings appeared as Springer LNCS 8172