1. KAIS T Message-In-a-Bottle: User-Friendly and Secure Key Deployment for Sensor Nodes Cynthia Kuo, Mark Luk, Rohit Negi, Adrian Perrig(CMU), Sensys07 2007. 11.22 Kim Taesung

2. A Secure Group Key Management Scheme for Wireless Cellular Network Contents Introduction Problem Definition, Assumptions and Attacker Model Protocol for Key Deployment Security Analysis Implementation Radio Measurement User Study MIB for Multiple Nodes Discussion Comparison Related Work Conclusion 2/20

3. A Secure Group Key Management Scheme for Wireless Cellular Network Introduction Deploying cryptographic key in a secure manner to sensor node is a prerequisite for secure sensor network. Secure key establishment rely on a pre-existing shared secret. TinySec, SPINS, ZigBee security. ZigBee security provides two suggestions Cryptographic keys could be sent in the clear. Factory could imprint keys on sensor nodes. Message-In-a-Bottle(MIB) Secure mechanism for initial key setup Four properties No physical interfaces Secure key deployment, wirelessly Key deployment by non-expert Batch deployment for multiple nodes 3/20

4. Problem Definition How can a shared secret be set up between a trusted base station and each new uninitialized node? Solution provides properties. Key secrecy Key authenticity Forward secrecy Demonstrative identification Robust to user error Cost effective No public key cryptography title 4/20

5. Protocol for Key Deployment MIB Participants Base Station The base station is not directly involved with key deployment. New Node Three states: uninitialized, initialized, and rejected Keying Device The keying device sends keying information to the new node when the Faraday cage is closed. Keying Beacon Three purposes: 1) detect when the Faraday cage is closed; 2) jam the communication channel; 3)inform the user of outcome of the deployment. User The user of MIB is the person who performs key deployment title 5/20

6. Overview of MIB Protocol Each mote has three color LEDs: Red, Green, and Blue. You will be working with three types of motes: Controller, Numbered Mote, Secret Keeper. Step 1. Verify that all three LEDs (red, green, and blue) on the Controller and the Secret Keeper are blinking simultaneously. Gently place the Numbered mote in the container. Step 2. Screw the cap on the container snugly. When no radio signals can escape the container, the Controller’s blue LED will be lit. Step 3. Wait until the Controller begins to blink its blue LED. This should take about 5 seconds. Step 4. Open the container and remove the Numbered mote. Record the result on the Results page. If the Controller’s green LED is lit, encryption keys were successfully exchanged. If the Controller’s red LED is lit, the key exchange process was not successful. It does not matter what color (if any) the Numbered mote is lit. title 6/20

7. Overview of MIB Protocol Why is a Faraday cage insufficient? In practice, Faraday cage is imperfect; it can not block radio signals completely. Usability issues. Protecting shielded messages Faraday cage. Messages are transmitted at minimum power. Keying beacon jams the wireless frequency. No spread spectrum. The secret key is a function of all the shielded messages. title 7/20

8. Detailed Description title 8/20

9. Notation title 9/20

10. Setup Keying Device and Keying Beacon title 10/20

11. Heartbeat Messages title 11/20

12. Deploy Cryptographic Keys title 12/20

13. Key Activation and Verification title 13/20

14. After Key Deployment Initialized node M Node identifies itself with ID M, counter c and keying device’s ID D. Base station can generate K M Base station possesses the master secret. title 14/20

15. Security Analysis Obtain Key K M through eavesdropping Inject a malicious key onto the new node Compromise the network by compromising the keying device Initiate key deployment before the Faraday cage Prevent the keying beacon from jamming during key deployment Wait for the user to make an error title 15/20

16. Implementation title 16/20

17. User study title 17/20

18. MIB for Multiple Nodes title 18/20

19. Comparison with Related Work 19/20 title

20. A Secure Group Key Management Scheme for Wireless Cellular Network Time for Any questions? Thank you for listening ! 20/20