This paper on reversed engineering was present by shaochun Xu of computer science, university of Windsor

1. Reverse Engineering
Computer Science
University of Windsor
Shaochun Xu

2. Contents
 What is Reverse Engineering (RE)?
 Why do we need Reverse Engineering?
 Scope and Tasks of Reverse Engineering
 Different Approaches
 RE tools
 Conclusions

3. What is Reverse
Engineering ?
 You have an unexpected case:
• You finished one course project using Java
• Your program runs OK
• But, by accident, you delete the java file
• How to hand in your project?

4. What is Reverse
Engineering ?
 You have an unexpected case:
• You finished one course project using Java
• Your program runs OK
• But, by accident, you delete the java file
• How to hand in your project?
 Reverse Engineering

5. What is Reverse
Engineering ?
Waterfall Model of software development
Requirement
analysis
design
Implementation
Testing and
Maintenance

6. What is Reverse
Engineering ?
Forward Engineering
Requirements
Design
Source Code
Behavior

7. What is Reverse
Engineering ?
Forward Engineering Reverse Engineering
Requirements
Design
Source Code
Behavior

8. What is Reverse
Engineering ?
Abstraction System
Old system New System
Forward Engineering
Re-Implementation
Reverse Engineering
Abstraction

9. What is Reverse Engineering?
 RE encompasses any activity that is done to
determine how a product works, to learn the
ideas and technology that were used in
developing that product.
 RE can be done at many levels
 RE generally belongs to Software
Maintenance

10. The Early Days of RE
 Law of Software Revolution (Lehman, 1980)
 Fundamental strategies for program
comprehension (Brooks, 1983)
 Taxonomy of Reverse Engineering
(Chikofsky&Cross, 1990)
 WCRE (Working Conference on R.E., 1990)
 IWPC (Int. Workshop on Program
Comprehension)

11. Why do we need RE ?
 Recovery of lost information
• providing proper system documentation
 Assisting with maintenance
• identification of side effects and anomalies
 Migration to another hw/sw platform
 Facilitating software reuse

12. Why do we need RE ?
 Benefits
• maintenance cost savings
• quality improvements
• competitive advantages
• software reuse facilitation

13. Difficulties of Reverse
Engineering
 Gap between problem
/solution domain
 Gap between concrete
and abstract
 Gap between coherency/disintegration
 Gap between hierarchical/associational

14. Scope and Task of Reverse
Engineering
 program understanding
Problem/Application
domain
Program/Implemen.
domain
Mapping

15. Scope and Task of Reverse
Engineering
 Redocumentation and/or document
generation
 Recovery of design approach and design
details at any level of abstraction
 Identifying reusable components and
components that need restructuring
 Recovering business rules
 Understanding high-level system
description.

16. Discovery of Abstraction
 Discovery of abstraction in large system
• maintenance purpose
• evolution purpose
• reengineering purpose

17. Levels of abstractions
 Application
• Application concepts, business rule, policies
 Function
• Logical and functional specification, non-functional
requirement
 Structure
• Data and control flow, dependency graphs
• Structure and subsystem charts
• Architectures
 Implementation
• Symbol tables, source text

18. Different Approaches
 Restructuring
• Transformation from one representation to
another at the same level,
Requirements
Design
Source code
Behavior

19. Different Approaches
 Reverse Engineering
• Design Recovery
– reproduce all the info for understanding the system
• Re-documentation
– provide different views of the system
 Re-Engineering
• first phase --understanding the system
• second phase--forward engineering

20. Different Approaches
Abstraction System
Old system New System
Forward Engineering
Re-Implementation
Reverse Engineering
Abstraction

21. Reverse Engineering Tools
 Analysis Tools
 Browsers
 Object Server
 Task Oriented Tools

22. Example--Java Decompiler
 How to recover bytecode from .class file
under Unix/Win with JDK?
% javap -c <filename>
% javap -help (to see the options)
 Java Decompilers
• ”ClassCracker” http://www.pcug.org.au/~mayon/
• “DeCafe Pro" from DeCafe, France at
http://decafe.hypermart.net/index.htm
• “SourceAgain" from Ahpah corp at http://www.ahpah.com

23. Example--Java Decompiler
 ClassCracker 2 Interface

24. Example--Java Decompiler
 Components of ClassCracker 2
• Java decompiler
– retrieves Java source code from Java class files
• Java disassembler
– produces Java Assembly Code
• A Java class file viewer
– displays Java class file structures.

25. Example--Java Decompiler
 Features of ClassCracker 2
• User visual interface.
• Can decompile class files within zip or jar files.
• Conversion mode (JAVA, JASM or JDUMP) is
selectable
• A Batc Mode allows multiple class files to be
decompiled simultaneously
• more…...

26. Example--Java Decompiler
 ClassCracker 2 System Requirements
• All platform (Window/Linus/Unix)
• JDK /JRE
 Do not believe it?
• From myClass_origin.class ==>myClass.java
• % javac myClass.java (==>myClass.class)
• % diff myClass.class myClass_origin.class

27. Example--Java Decompiler
 ClassCracker 2.0--want to try it?
• Free download at
http://www.pcug.org.au/~mayon/classcracker/
ccgetdemo.html
• Only first three methods are decoded.
 Bridge 1.0---Free
• http://www.geocities.com/SiliconValley/
Bridge/8617/jad.html

28. Conclusions
 Reverse Engineering is a new research area
among software maintenance
 RE includes activities of understanding the
system and recovery info from system
 Program understanding is the most important
subset of Reverse Engineering
 Discovery of abstraction is key issue

29. Questions ?