Restricted and Mobile: Security in Mobile Wireless Sensor Networks Kısıtlı ve Hareketli: Mobil Telsiz Duyarga Ağlarında Güvenlik

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1 Restricted and Mobile: Security in Mobile Wireless Sensor Networks Kısıtlı ve Hareketli: Mobil Telsiz Duyarga Ağlarında Güvenlik Albert Levi Sabancı University Computer Science and Engineering 1 MWSN Security, Albert Levi

2 Agenda Wireless Sensor Networks (WSN) and mobility Existing literature on key distribution in WSNs Our work on key distribution for Mobile WSNs Our work on key distribution for Underwater WSNs Our work on wormhole detection in Mobile WSNs 2 MWSN Security, Albert Levi

3 Wireless Sensor Networks >10 years Complex and challenging set of problems Including security A computing paradigm Vast amount of sensor nodes distributed over a field Both sensing (temperature, pressure, humidity, etc.) and short-range wireless communication capabilities Ultimate aim is to carry the sensed data (possibly after an in-network processing) towards a sink node Sensor nodes are small, low-cost, low-power devices with limited memory, computational power and energy communicate on short distances sense environmental data perform limited data processing 3 MWSN Security, Albert Levi

4 Wireless Sensor Networks Random deployment Inaccessable terrains, disaster relief operations, military fields Difficult to control Self-organized network protocols and algorithms Static & Mobile By themselves Due to environmental factors such as wind, or water Due to deployment of sensor nodes on moving objects E.g. ZebraNet, habitat monitoring, collect information about zebras migration an behavior pattern 4 MWSN Security, Albert Levi

5 Our Motivation Research on mobile WSNs addresses coverage problem, deployment of the network, routing problems, etc. However, security issues have not been studied much, especially compared to static WSNs TÜBİTAK 110E180 Project March 2011 August 2013 Aim is to investigate security issues in Mobile WSNs in particular, key distribution problem, which is the most basic problem existing key distribution schemes for WSNs focus on static WSNs There is a lack of key distribution schemes for mobile WSNs Motto: intelligent use of mobility for the benefit of security 5 MWSN Security, Albert Levi

6 Literature on Key Distribution in WSNs Naive Solutions Use one key for all the nodes Use pairwise-keys for all the nodes and keep all the keys in the memory Probabilistic solutions Sometimes used in combination with polynomial or matrixbased (e.g. Blom s) schemes Location-aware solutions Combinatorial designs Solutions that pay attention to mobility 6 MWSN Security, Albert Levi

7 Basic Scheme Random Key Predistribution Original idea by Eschenauer and Gligor (ACM CCS 2002) Key predistribution: Pick some keys randomly out of a global key and put them into nodes key chains before the deployment Shared Key Discovery: If two nodes share at least one key they can communicate Path-key Establishment: If they do not have direct secure link, they use neighbors to establish a key 7 MWSN Security, Albert Levi

8 Du et al. s Scheme An improvement on Basic Scheme using deployment knowledge by Du et al. (INFOCOM 2004) A zone-based Gaussian deployment model is used Nodes that will be close to each other after deployment would share keys Distant nodes will not share keys Global key pool is distributed among zones so that nodes from neighboring zones share key Key pre-distribution, shared-key discovery and path-key establishment phases 8 MWSN Security, Albert Levi

9 Local Connectivity for Basic Scheme and Du s Scheme for static WSNs Local connectivity: probability of any two neighboring nodes sharing a key Du s scheme performs better Makes use of location information 9 MWSN Security, Albert Levi

10 Effects of Mobility on Basic Scheme and Du et al. s Scheme No change in Basic Scheme Keys are distributed without any regard to location info. Decrease in Du s scheme Depends on location information Neighboring relationships change 10 MWSN Security, Albert Levi

11 A perfectly resilient key distribution scheme for Mobile WSNs Nodes and the Base Station (BS) are mobile. BS operates as a key distribution center. Nodes are not preloaded with any keys. After they are deployed to the area, BS starts to move among the nodes and distribute pairwise keys to neighboring nodes it meets along the way. In our scheme, we use Random Walk Mobility Model K. Karaca and A. Levi, "Resilient Key Establishment for Mobile Sensor Networks", MobiSensor Second International Workshop on Mobility in Wireless Sensor Networks, June 29, 2011, Barcelona, Catalonia, Spain. 11 MWSN Security, Albert Levi

12 Random Walk Mobility Model Choose a random direction between [0, 2 п] and a random speed between [speedmin, speedmax] Move in that direction with that speed for a constant time t or a constant distance d. If the boundary is reached, bounce back 12 MWSN Security, Albert Levi

13 Movement of BS S A deterministic approach to ensure that BS scans the whole area and meets with possibly all the nodes. BS starts moving from southwest corner of the area, goes to the opposite edge horizontally. After it gets very close to the boundary, it starts moving vertically for a very short distance, and then starts moving horizontally again. When it scans the whole area, it diagonally goes back to the southwest corner and starts its movement from there again. 13 MWSN Security, Albert Levi

14 Details of Our Scheme 4 components: Initialization phase, key distribution, shared-key discovery, update of the key chain Initialization Phase A shared key between BS and each node prior to deployment No other predistributed keys Nodes deployed to the area using uniform random distribution Key Distribution Starts when a node senses BS in its communication range BS generates and sends random pairwise keys to nodes using a Needham-Schroeder-like secure protocol. 14 MWSN Security, Albert Levi

15 Shared Key Discovery When two nodes want to communicate they exchange their node IDs If they have a pairwise key in their key chains, they can communicate with each other using that key 15 MWSN Security, Albert Levi

16 Update of the Key Chain Fixed key chain size for nodes Key chain is updated in first-in-first-out manner If there is no space in key chain, node deletes the first not used key and adds the new key to the key chain 16 MWSN Security, Albert Levi

17 Performance Metrics Local Connectivity probability of any two neighboring nodes sharing a common key Global Connectivity ratio of the largest isolated component to the whole network Resilience against node capture attacks A measure of additionally compromised links in case some nodes are captured by an attacker 17 MWSN Security, Albert Levi

18 Local Connectivity for Different m Values Local connectivity values between (0.42, 0.54) Little difference with respect to m Number of neighbors is more decisive (average 60, max 90) Takes time to reach steady state One round of movement for BS 18 MWSN Security, Albert Levi

19 Local Connectivity for Different BS Speed Values Local connectivity values between (0.31, 0.51) Increase in local connectivity as BS speed increases BS meets the nodes more frequently and distributes fresh keys Takes less time to reach steady state for high BS speeds Covers the area faster 19 MWSN Security, Albert Levi

20 Global Connectivity Global connectivity reaches steady state value very close to 1 after BS completes its one round 20 MWSN Security, Albert Levi

21 Resilience If a node is captured, all keys that this node carries are compromised This causes some other links that these keys are used to be compromised as well Resilience is the measure of how many additional links are compromised in case of node captures In our scheme, BS distributes pairwise keys to the nodes Nodes do not keep pairwise keys of other nodes Even if an attacker captures a number of nodes and gets access to the keys carried by those nodes, it can only compromise the links of the already captured nodes. It cannot compromise any additional links with the help of those keys Therefore our scheme has perfect resiliency against node capture 21 MWSN Security, Albert Levi

22 Conclusions for the first part We propose a key distribution scheme for Mobile Wireless Sensor Networks Our scheme achieves a local connectivity value higher than the Basic Scheme and lower than the original Du s Scheme, but a higher value than the Du s Scheme shows when the nodes are mobile Our scheme provides perfect resilience against node capture 22 MWSN Security, Albert Levi

23 Key Distribution in Underwater Wireless Sensor Networks (UWSNs) UWSNs is a type of WSNs More challenging Acoustic waves have to be used which have large latency, low bandwidth and high error-rate. Currents results in mobility UWSN is a recent research area There was no proposed scheme for key distribution. In this work, we proposed two key distribution models for UWSNs. K. Kalkan and A. Levi, " Key Distribution Scheme for Peer-to-Peer Communication in Mobile Underwater Wireless Sensor Networks ", Peer to Peer Networking and Applications (Springer), accepted for publication, October DOI: /s MWSN Security, Albert Levi

24 Mobility Model used in Our Scheme Group Mobility Models Nomadic Community Mobility Model 24 MWSN Security, Albert Levi

25 Mobility Model used in Our Scheme Meandering Current Mobility Model * Dynamics of water is considered in this mobility model This model is for large environment that spans several kilometers. It is a two dimensional model. Depends on this stream function: *A. Caruso, F. Paparella, L.F.M. Vieira, M. Erol, and M. Gerla, The Meandering Current Mobility Model and its Impact on Underwater Mobile Sensor Networks. In Proceedings of INFOCOM. 2008, MWSN Security, Albert Levi

26 *A. Caruso, F. Paparella, L.F.M. Vieira, M. Erol, and M. Gerla, The Meandering Current Mobility Model and its Impact on Underwater Mobile Sensor Networks. In Proceedings of INFOCOM. 2008, MWSN Security, Albert Levi

27 Hierarchical Scheme Surface buoys (equipped with powerful computational devices) Elevators Ordinary nodes in groups Network Architecture 27 MWSN Security, Albert Levi

28 Communication Patterns Elevator to Elevator Communication Node to Node Communication in Different Groups from Different Elevators Node to Node Communication in Different Groups from Same Elevator Node to Node Communication in Same Group Elevator to Node Communication 28 MWSN Security, Albert Levi

29 Communication Patterns Elevator to elevator communication By the help of surface buoys through the air with a pairwise key. 29 MWSN Security, Albert Levi

30 Communication Patterns Elevator to node communication By using pairwise keys Node to node communication in same group By using Blom s common key 30 MWSN Security, Albert Levi

31 Communication Patterns Node to node in different groups that belong to same elevator communication By the help of the elevator 31 MWSN Security, Albert Levi

32 Communication Patterns Node to node in different groups that belong to different elevators communication By the communication of their elevators 32 MWSN Security, Albert Levi

33 Nomadic Mobility Model 33 MWSN Security, Albert Levi

34 Key Establishment Phases Before Deployment Phase After Deployment Phase Operational Phase 34 MWSN Security, Albert Levi

35 Before Deployment Phase Surface buoy & Elevator unit is loaded with private matrix A and public matrix G for each group A node is loaded with: its own ID ID of the owning elevator A row of the private matrix A Seed of the public matrix G Prime number q 35 MWSN Security, Albert Levi

36 After Deployment Phase 36 MWSN Security, Albert Levi

37 Operational Phase 37 MWSN Security, Albert Levi

38 Performance Evaluation Secure Connectivity : Probability of sharing common key between any two neighbor nodes 38 MWSN Security, Albert Levi

39 Performance Evaluation Additionally Compromised Links Ratio: It is a measure that shows how many extra links are reached by the attacker after some nodes are captured. 39 MWSN Security, Albert Levi

40 Performance Evaluation Totally Compromised Links Ratio: It is measure that shows not only additionally compromised links but also all links that are compromised by the attacker. 40 MWSN Security, Albert Levi

41 Network Architecture for Meandering Model 41 MWSN Security, Albert Levi

42 Communication Patterns Underwater Device to Node Underwater Device to Underwater Device Node to Node in Same Group Node to Node in Different Groups from Different Underwater Devices Node to Node in Different Groups from Same Underwater Device 42 MWSN Security, Albert Levi

43 Key Establishment Phases Before Deployment Phase After Deployment Phase Operational Phase Difference: Changing the places of surface buoys during the operations 43 MWSN Security, Albert Levi

44 Performance Evaluation Secure Connectivity : Probability of sharing common key between any two neighbor nodes 44 MWSN Security, Albert Levi

45 Performance Evaluation Additionally Compromised Links Ratio: It is a measure that shows how many extra links are reached by the attacker after some are captured. 45 MWSN Security, Albert Levi

46 Performance Evaluation Totally Compromised Links Ratio: It is measure that shows not only additionally compromised links but also all links that are compromised by the attacker. 46 MWSN Security, Albert Levi

47 Conclusions for the second part We proposed a key distribution scheme for underwater mobile sensor networks We applied key distribution scheme for two mobility models : nomadic mobility and mendering mobility model Both models are hierarchical networks For both models Blom s scheme is utilized Nomadic based model is 3-D and a small limited area model whereas meandering is 2-D and a large boundless area model Reduction in secure connectivity due to mobility self-heals for both models Both models are highly resilient to capture attacks Both models are energy efficient 47 MWSN Security, Albert Levi

48 Wormhole Attacks Adversaries tunnel packets received on one part of the network to another part Wormholes may convince two nodes that they are close to each other in fact they are far away from each other Generally implemented via a low-latency communication channel available only to the attackers Disorders routing and data dissemination Generally used together with sinkhole and selective forwarding 48 MWSN Security, Albert Levi

49 Wormhole Detection in MWSNs Motivation Majority of the solutions for sensor network considers only static networks Mobile solutions are mostly for ad-hoc networks Not applicable to sensor networks directly due to limitations in sensor network Our Contribution in a Nutshell A distributed statistical wormhole detection scheme for mobile wireless sensor networks No requirement for central controllers, GPS receivers, tight clock syncronization, specialized hardware or nodes Utilize mobility of sensor nodes to estimate two network features locally via using neighboring information Network density Standard deviation in the network density Wormhole attack is detected via observing anomalies in the neighbor nodes behaviors based on the estimated values O. Şimşek and A. Levi, "A Distributed Scheme to Detect Wormhole Attacks in Mobile Wireless Sensor Networks", In Proceedings of ISCIS th International Symposium on Computer and Information Sciences, pp , Springer, London, UK, September MWSN Security, Albert Levi

50 Wormhole Detection in MWSNs Workflow of the Proposed Scheme Local and global thresholds to blame a node as wormhole All parametric With properly selected parameters the detection rate can go up to 100% with a false positive rate between 0.3% and 1.5% 50 MWSN Security, Albert Levi

51 Thanks Questions? 51 MWSN Security, Albert Levi