1. Secure and Efficient Key Management in Mobile Ad Hoc Networks Bing Wu, Jie Wu, Eduardo B. Fernandez, Mohammad Ilyas, Spyros Magliveras Department of Computer Science and Engineering, Florida Atlantic University, Boca Raton, FL 33431, USA Department of Mathematics, Florida Atlantic University, Boca Raton, FL 33431, USA Journal of Network and Computer Application Present: Jhoong-Wei Chen

2. Introduction The ad hoc networks security Introduce a secure and efficient key management scheme(SEKM) The basic idea is that server nodes form an underlying service group

3. Key Management in Ad Hoc Networks Trust models

4. Secure and Efficient Key Management (SEKM) Scheme Notation and assumption –that every node carries a valid certificate from off-line configuration before entering the network

5. Secure and Efficient Key Management (SEKM) Scheme The overview of SEKM –K ca -1 is distributed to m shareholders (server) –A quorum of k(1<k≤m) servers (server group) can produce a valid certificate –SEKM group maintenance phases share updating phases certificate renew/revocation phases handling new server nodes phases

6. Secure and Efficient Key Management (SEKM) Scheme Secure server group formation and maintenance –Use mesh structure –only server nodes initiate the group formation and become members of the group –A subset of non-server nodes could be forwarding nodes –the tree-based structure is easy to break in a high dynamic situation and incurs excessive control traffic –Soft state

7. Secure and Efficient Key Management (SEKM) Scheme Group Creation –When a secret shareholder enters the network, it broadcasts a JoinServeReq: {ID i, SEQ i, TTL} {[h(ID i, SEQ i )]K i -1 |(TTL)K i -1 } –When a node –receives a non-duplicate JoinServerReq packet, it needs to verify that the packet is from the authenticated source –The TTL value decreases by 1 as the packet leaves intermediate node. The change of TTL is signed by intermediate nodes

8. Secure and Efficient Key Management (SEKM) Scheme –If the server node receive JoinServerReq it will send a JoinServerReply packet as well as forwarding the request packet. –JoinServerReply packet is also protected by the replier’s signature

9. Secure and Efficient Key Management (SEKM) Scheme Group maintenance –for a mesh structure, there are multiple possible paths between pairs of servers –the periodical message JoinServerRequest and JoinServerReply are sent out

10. Secure and Efficient Key Management (SEKM) Scheme Secret share updating –k servers within the server group initiate the share update phase –At every round every server i generates a random number β i between 0 and 1 and a threshold value τ i. τ i is defined as

11. Secure and Efficient Key Management (SEKM) Scheme Secret share updating

12. Secure and Efficient Key Management (SEKM) Scheme Handling new servers –server group updates shares periodically, a new joining node could carry an outdated share from off-line configuration –A message could be –A message sent out to notify requesting node r by checking the version field in the certificate

13. Secure and Efficient Key Management (SEKM) Scheme Certificate updating

14. Secure and Efficient Key Management (SEKM) Scheme Certificate updating

15. Secure and Efficient Key Management (SEKM) Scheme Handling certificate expiration and revocation –A certificate will expire after a predetermined period of time –In this paper, for simplicity, a –node with an expired certificate needs some off-line or in-person reconfiguration –A node’s certificate could be revoked by the server group within its validity period for several reasons

16. Performance evaluation Assumption –100 X100 2-D free-space –from 40 to 100 nodes –transmission range r =25 –1024-bit RSA cryptographic key pairs –The coefficients of the polynomial are 512 bits long. –hashed using MD5 –implemented in Matlab.

17. Performance evaluation

20. Conclusion In this paper we propose a key management scheme, SEKM, which creates a PKI structure for this type of Ad Hoc Networks SEKM is that it is easier for a node to request service from a well maintained group rather than from multiple ‘‘independent’’ service providers which may be spread in a large area.

21. Appendix Key agreement protocol: A key agreement protocol or mechanism is a key establishment technique in which a shared secret is derived by two (or more) parties as a function of information contributed by, or associated with, each of these, (ideally) such that no party can predetermine the resulting value. Key management protocol: