1. Intelligent Database Systems Lab 國立雲林科技大學 National Yunlin University of Science and Technology A Plagiarism Detection Technique for Java Program Using Bytecode Analysis Presenter : Shu-Ya Li Authors : Jeong-Hoon Ji, Gyun Woo, and Hwan-Gue Cho ICCIT, 2008

2. Intelligent Database Systems Lab N.Y.U.S.T. I. M. 2 Outline Motivation Objective System overview Methodology Experiments and Results Conclusion Comments

3. Intelligent Database Systems Lab N.Y.U.S.T. I. M. Motivation Plagiarism can be a big problem in universities and companies.  In MIT, about 30% of students were punished due to plagiarism. Most plagiarism detection systems evaluate the similarity of source codes.  the source code security can be a significant problem. 3

4. Intelligent Database Systems Lab N.Y.U.S.T. I. M. Objectives A new plagiarism detection technique for Java programs  Using bytecodes without referring their source codes. 4 Class File (Bytecode) g9623702.java Source code CompilerInterpreter 0011010011101001… g9623702.classg9623701.classg9623703.class Plagiarism detection

5. Intelligent Database Systems Lab N.Y.U.S.T. I. M. System overview 5 Class File (ByteCodes) Constant Pool Analysis Class Collection ByteCode Linearization Token Sequences ByteCode Grouping Static Method Analysis Token Sequences Adaptive Local Alignment Similarity Matrix Similarity Measure Similarity (a) Generating token sequences(b) Evaluating the similarity ByteCode Grouping Static Method Analysis Constant Pool Analysis Class Collection ByteCode Linearization Adaptive Local Alignment Similarity Measure

6. Intelligent Database Systems Lab N.Y.U.S.T. I. M. Bytecode Linearization ByteCode Grouping 6 The results of linearization for two programs P a and P b PaPb

7. Intelligent Database Systems Lab N.Y.U.S.T. I. M. Bytecode Linearization Static Method Analysis 7 sum() → main() main() → sum() → min()

8. Intelligent Database Systems Lab N.Y.U.S.T. I. M. Adaptive Local Alignment & Similarity Measure 8 bc_push bc_store bc_store - Local alignment algorithm Adaptive local alignment +1 point -2 point +1 point 根據 keywords 出現頻率

9. Intelligent Database Systems Lab N.Y.U.S.T. I. M. Experiments 9

10. Intelligent Database Systems Lab N.Y.U.S.T. I. M. Conclusion we presented an automatic Java byte code comparison system PINT B for detecting plagiarism in Java bytecodes. 10

11. Intelligent Database Systems Lab N.Y.U.S.T. I. M. Comments Advantage  A new plagiarism detection method Drawback Application  Source code analysis 11