1. Automated Analysis of Cryptographic Protocols Using Murphi Mingchen Zhao University of Pennsylvania

2. Outline Background – Model checking – Authentication protocol Outline of methodology Needham-Schroeder public-key protocol (with bug) Demo of Murphi Needham-Schroeder public-key protocol (with Lowe’s fix) Demo of Murphi Comparison between Model checking and Inductive Method

3. Background-Model checking Pioneering Work by Edmund M. Clarke, E. Allen Emerson and Joseph Sifakis Awarded 2007 Turing Award Definition: Model checking is a technique for automatically verifying correctness properties of finite state systems.

4. Model Checking Example P_{0}:: l_{0} : while True do NC_{0}: wait (turn=0); CR_{0}: turn:=1; end while; l’_{0} P_{1}:: l_{1} : while True do NC_{1}: wait (turn=1); CR_{1}: turn:=0; end while; l’_{1}

5. Model Checking Example

6. Authentication Protocol Needham-Schroeder Public-Key protocol – The Needham–Schroeder Public-Key Protocol is intended to provide mutual authentication between two parties communicating on a network, but in its proposed form is insecure.

7. Authentication Protocol – Imaging that you lost your debit card… How do you prove that you the person you claimed? Name? Photo? Birthday? SSN? Password? In cryptographic protocol, we trust you only when you have the private key.

8. Outline of Methodology Formulate the protocol Add an adversary to the system State the desired correctness condition Run the protocol for some specific choice of the system size parameters. Experiment with alternate formulations and repeat

9. NS public-key protocol (with bugs) Can anyone see the problem of this protocol?

10. Demo Murphi Ssh

11. NS public-key protocol (with Lowe’s fix)

12. Demo Murphi Ssh

13. Comparison between Model Checking and Inductive Method Model CheckingInductive approach Checking abilityFinite-State (Not only finite, the states increased exponentially with the size) Infinite-State Human Intelligence Involved Modeling PhaseThe whole process Easy-to-usePeople who can program Mathematician or Ph.D in corresponding area?