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Securing Wireless Mesh Networks Yanchao Zhang Department of Electrical & Computer Engineering New Jersey Institute of Technology In collaboration with:

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Presentation on theme: "Securing Wireless Mesh Networks Yanchao Zhang Department of Electrical & Computer Engineering New Jersey Institute of Technology In collaboration with:"— Presentation transcript:

1 Securing Wireless Mesh Networks Yanchao Zhang Department of Electrical & Computer Engineering New Jersey Institute of Technology In collaboration with: Professor Yuguang “Michael” Fang Department of Electrical & Computer Engineering University of Florida 2007 Network/Computer Security Workshop Lehigh University, May 2007

2 2/43 Roadmap Introduction to wireless mesh networks u Necessity, architecture, state of the art Security issues Our solutions Conclusion & future work

3 3/43 Mesh Networks: why do we need them? Ubiquitous broadband Internet access RNC PSDN Internet Cellular networks Wide area coverage (km range) Low speed High deployment costs W-CDMA: 384 kb/s ~ 2 Mb/s CDMA2000: 144 kb/s ~ 2.4 Mb/s

4 4/43 Mesh Networks: why do we need them? Ubiquitous broadband Internet access Wireless LAN Interne t Small coverage (up to 300m for 802.11) High speed 802.11b: 11 Mb/s, 802.11a/g: 54 Mb/s, 802.11n : 540 Mb/s Low deployment costs

5 5/43 Wireless Mesh Networks (WMNs) Internet WiMaxT1/E1 mesh mesh router (Akyildiz et al., 2004)

6 6/43 Merits of Wireless Mesh Networks High speed Extended coverage (multi-hop comm.) Low deployment costs High robustness (multiple routes) Simple configuration and maintenance Good network scalability …

7 7/43 Application Scenarios Broadband home networking Community and neighborhood networking Enterprise networking Metropolitan area networks Intelligent transportation systems Security surveillance systems Building automation …

8 8/43 State of the Art Academia u SIGCOMM, INFOCOM, MobiCom, MobiHoc, ICNP, ICDCS, IEEE JSAC … u MIT, CMU, Rice, Georgia Tech, UCSB, UF, Stony Brook … Industry u Microsoft, Intel, Nortel, Nokia, MeshNetworks (Lucent), Tropos, Kiyon, BelAir, Strix, SkyPilot, MeshDynamics … Standardization activities u IEEE 802.11/15/16 Deployment practices u Seattle, New York, San Francisco, London, Rome, Paris…

9 9/43 Roadmap Introduction to wireless mesh networks u Necessity, architecture, state of the art Security issues Our solutions Conclusion & future work Other security projects

10 10/43 Classification Infrastructure security u Security of signaling and data traffic transmitted over the wireless mesh backbone Application security u Security of mesh clients’ concrete applications Network access security u Security of communications among a mesh router and mesh clients it serves

11 11/43 Network Access Security Why difficult to achieve? u Mesh routers are designed to accept open access requests from most likely unknown mesh clients u Open access to wireless channels u Multi-hop, cooperative communications u Dynamic network topology due to client mobility Internet WMN backbone Our goal

12 12/43 Network Access Security Issues Router-client authentication Router-client key agreement Client-client authentication Client-client key agreement Internet WMN backbone Our goal

13 13/43 Network Access Security Issues Bogus-beacon flooding attack u Allowing the attacker to ­Beguile mesh clients into always processing beacons ­Impede the Internet access of mesh clients Internet WMN backbone mesh beacon bogus beacon

14 14/43 Network Access Security Issues Incontestable billing Location privacy u Mesh clients can travel incognito Secure routing and MAC protocols When Internet marries multi-hop wireless u DoS/DDoS mitigation, worm detection & prevention, IP traceback, intrusion detection …

15 15/43 Our Solutions Router-client authentication Router-client key agreement Client-client authentication Client-client key agreement Mitigating bo gus-beacon flooding attack Incontestable billing Location privacy

16 16/43 Network Model A large-scale WMN comprises many domains u Each domain is operated by an independent network operator of arbitrary scale Multi-hop uplink u A mesh client transmits packets in one hop or multiple hops to the mesh router Single-hop downlink u The router sends packets in one hop to all clients u Merits: save energy of clients; facilitate the transmission of signaling data …

17 17/43 Old Home-Foreign Trust Model Difficult to establish pairwise roaming agreements among numerous WMN operators Significant authentication signaling traffic u May invite DoS/DDoS attacks Long authentication latency Irresolvable billing disputes Internet/ PSTN Foreign domain Home domain trust roaming agreement (Used by cellular & mobile IP networks)

18 18/43 Our Model: Client-Broker-Operator operator 1operator n broker 2broker 1 pass # of brokers << # of WMN operators

19 19/43 Merits of Client-Broker-Operator Model For mesh clients u Enjoy single-sign-on on-demand broadband Internet access from any WMN operator For WMN operators u Just need to trust one or a few brokers u Have all mesh clients as potential customers u Reduce administration & customer-service costs For brokers u Make profits by imposing transaction/subscription fees to mesh operators/clients

20 20/43 Notation

21 21/43 Public-Key Cryptography (PKC) Everyone has a unique public/private key pair Certificate-based PKC (e.g., RSA or DSA) u Alice’s public key, pub A, is a random string u Need a certificate binding pub A to Alice u cert A := ID-based PKC (by Shamir, 1984) u Alice’s pub A can be her publicly known identity information such as her email address u No need for certificates

22 22/43 The Pairing Technique Pairing parameters can be predefined by standards bodies such as IETF, as is done for Diffie-Hellman parameters for use in IPsec

23 23/43 Router Pass (R-PASS) Operator O i :

24 24/43 Client Pass (C-PASS) Broker B i :

25 25/43 Authentication & Key Agreement (AKA) Inter-domain router-client AKA u A client roams from a WMN domain to another Intra-domain router-client AKA u A client roams in the same WMN domain Client-client AKA u Two clients in the same WMN domain perform AKA

26 26/43 Inter-Domain Client-Router AKA

27 27/43 Inter-Domain Client-Router AKA Key agreement

28 28/43 Intra-Domain Router-Client AKA

29 29/43 Client-Client AKA Client-client AKA u Two clients ascertain that they are served by the same WMN domain u Two clients establish a shared key to encrypt and authenticate traffic between them u Can be done on demand

30 30/43 Client-Client AKA

31 31/43 Our Solutions Router-client authentication Router-client key agreement Client-client authentication Client-client key agreement Mitigating bogus-beacon flooding attack Incontestable billing Location privacy

32 32/43 Bogus-Beacon Flooding Attack Allowing the attacker to u Deceive mesh clients into endless signature verifications to check authenticity of beacons u Impede the network access of mesh clients Defense: one-way hash chain Internet WMN backbone mesh beacon bogus beacon

33 33/43 Defense against Bogus-Beacon Flooding Router R 1,1  Select an integer n and a random secret b n  Compute b y = h(b y+1 ), for 1 ≤ y ≤ n-1  Deriving b y from b y+1 is very efficient, but the opposite is computationally infeasible

34 34/43 Defense against Bogus-Beacon Flooding message authentication code

35 35/43 Defense against Bogus-Beacon Flooding message authentication code

36 36/43 Defense against Bogus-Beacon Flooding Analysis  A router performs one signature generation every n broadcast beacons  A client carries out one signature verification every n broadcast beacons

37 37/43 Incontestable Billing Challenges u WMN operators may overcharge u Mesh clients may deny the received network services u Intermediate clients desire reward for forwarding traffic Our solution: a real-time hash-chain approach

38 38/43 Incontestable Billing C 1,1  Create a one-way hash chain with each hash value associated with a monetary value x 0  Send the signed ( b 1, x 0 ) to R 1,1 as a payment commitment u Periodically release hash values in sequence R 1,1  Record the signed ( b 1, x 0 ) and the last b m s.t. b 1 =h m-1 (b m )  Redeem b m at broker B 1 and get paid mx 0

39 39/43 Incontestable Billing How to pay intermediate clients?  C 1,1 pays R 1,1 what R 1,1 and others should get  R 1,1 pays each client using the hash-chain approach  Merit: each client just has a payment relationship with R 1,1 instead of each of other clients Analysis u Each client must pay in real time to avoid service cutoff u He cannot deny the payment due to the signed commitment u Operators cannot fake hash values to overcharge clients

40 40/43 Location Privacy Mesh clients prefer to travel incognito u Remain anonymous to both visited WMN operators and potentially malicious eavesdroppers Solution u A client uses dynamic (pass, pass-key) pairs u A secure, lightweight way to refresh client pass/pass-key pairs

41 41/43 Conclusion Identified security requirements & challenges in multi-hop wireless mesh networks Proposed a client-broker-operator trust model Presented efficient solutions to u Router-client and client-client AKA u Mitigating bogus-beacon flooding attack u Incontestable billing u Location privacy

42 42/43 Future Work Secure wireless mesh backbone Secure routing and MAC protocols When Internet marries multi-hop wireless u DoS/DDoS mitigation u Worm detection & prevention u IP traceback u Intrusion detection u …

43 43/43 References u Y. Zhang and Y. Fang, “ARSA: An Attack-Resilient Security Architecture for Multihop Wireless Mesh Networks,” IEEE JSAC, 24(10), Oct. 2006 u Y. Zhang and Y. Fang, “A Secure Authentication and Billing Architecture for Wireless Mesh Networks,” ACM Wireless Networks, to appear


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