1. Validating and Securing Spontaneous Associations between Wireless Devices Author: Tim Kindberg, Kan Zhang Presented by: 魏聲尊

2. Outline Question Statement Introduction Scenario Conclusion

3. Question Statement

4. Introduction They expect a frequently encountered task in mobile and ubiquitous computing will be make spontaneous associations between devices over wireless networks. They use RF and ultrasound.

5. Scenario

6. Physically validating an association 0.A discovery service provide the PDA with a list of participating 1.PDA ----  printer A: locate message contain its identifier 2.printer A ----  PDA:(a) an RF message acknowledge the locate (b) ultrasound message 3.PDA record the time and verifier that identifiers in the RF and ultrasound match.

7. Secure association with one-way validation 1.Client ----  Target: ‘associate’ 2.Target ----  Client: N1,K p (RF message) Target ----  Client: N1(ultrasound message) N1:random number, K p : public key 3.Client check N1 4.Client ----  Target: N1,{K}K p K: session key 5. Target check N1

8. Shortcomings The location of the responding device is ambiguous. Reflection, diffraction etc.

9. Conclusion They introduce solutions for (a) physically validating a wireless association such that one or both parties can verify with which device they have associated (b) securing an associate so that data exchanged using the association cannot be eavesdropped or tampered with. Their technique allow association with any device in line of sight.