Secure Your Application With Pattern Oriented Design Chia Yuen Kwan, Senior Lecturer & Consultant, Software Systems Practice

1. Secure your application with
Pattern Oriented Design
Chia Yuen Kwan
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2. Problem-Solution-Reuse
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Christopher Alexander (4 October 1936 – 17 March 2022)
(an architect)
• Designed and built over 100 buildings
• Regarded as the father of the pattern
language movement
• Many urban development projects continue to
incorporate Alexander's ideas.

3. Agenda
• Design Pattern
• Secure Design Pattern
• Secure Strategy Pattern
• Q&A
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4. Case Study –
A Shopping Cart Application
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5. Initial Design
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sum of (price
* qty)

6. Special Requirement
• eCommerce Operators run special events
• During Christmas Day, the price will be marked up by 10%!
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7. Initial Design - Problem
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sum of (price
* qty)

8. Initial Design – Class Diagram
• Does not leverage on the principle of Polymorphism!
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if-else
statement to
compute total
based on
different
occasions

9. Solving the problem with
Design Pattern
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Look for an
appropriate
Pattern
Adopt the solution

10. Design Patterns by Gang of Four
• GOF-
• Erich Gamma, Richard Helm, Ralph Johnson,
John Vlissides
• Collection of 23 design patterns
• Capture solutions that have evolved over time
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11. Solution – Strategy Pattern
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Context
+contextInterface()
-strategy
1
*
Strategy
+algorithmInterface()
ConcreteStrategyA
+ConcreteStrategyA()
+algorithmInterface()
ConcreteStrategyB
+ConcreteStrategyB()
+algorithmInterface()
Client -context
implements
a compliant
algorithm
superclass
subclasses
inherits

12. Adopting the Strategy Pattern
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contains
Initial Design –
Class Diagram
After applying Strategy Pattern –
Class Diagram
inherits

13. Strategy Pattern –
Sequence Diagram
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Initial Design –
Sequence Diagram
After applying Strategy Pattern –
Sequence Diagram

14. Benefits- Strategy Pattern
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contains
• Cohesiveness of the programs
• Robust Design
• Increate in productivity!
After applying Strategy Pattern –
Class Diagram
inherits

15. Secure Software Design
• Secure Strategy Pattern
• The need to deploy different security mechanisms into different environments
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16. Cryptography – Various Algorithm
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Cryptography
Encryption
Symmetric
(Secret Key)
Asymmetric
(Public Key)
Hashing

17. Attacks on Cryptography
• Brute Force Attack
• Dictionary Attack
• Rainbow Attack
• Involves a rainbow table containing hashed common passwords
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18. Secure Strategy Pattern
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Different Cryptographic algo to be
executed base don configuration settings

19. Secure Factory and Secure Strategy Pattern
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20. Conclusion
• Borrow “ready made” design solution
• Proven working solutions
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21. Q&A
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Survey 1 – Topics

22. Q&A
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Survey 1 – Topics Survey 2 -Day 1 Programme

23. Give Us Your Feedback
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Day 1 Programme

24. Thank You!
isscyk@nus.edu.sg
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