Secure Multipath Routing Protocol for Wireless Sensor Networks

1. Secure Multipath Routing Protocol for Wireless Sensor Networks Bharat Reddy AnkushadharJoliholi

2. Agenda Introduction/Motivation Overview & Assumptions of SEER Seer Phases Topology Construction Data Transmission Route Maintenance Security of SEER Wormhole & Sinkhole attacks Selecting Forwarding attacks Performance Evaluation Conclusion

3. Introduction/Motivation Problem: Designing an energy efficient and secure routing protocol for Wireless Sensor Networks(WSN) Traditional Ad-Hoc Network routing protocols like AODV & DSR can’t be used in WSNs as WSNs are different from Ad-Hoc Networks capacity wise, size wise etc. Possible Solution: Use Multipath mechanism used in traditional networks as well as in Ad-Hoc Networks Weaknesses: Additional overhead(energy consumed) to maintain multiple paths Optimal path is found and is used repeatedly thus reducing the energy levels of the nodes on the optimal path causing energy disparity Security is almost non-existent Authors propose a new protocol called SEER (Secure and Energy-Efficient Multipath Routing) protocol

4. SEER Overview & Assumptions

5. SEER overview SEER uses Client-Server architecture Base Station acts as the Server and the sensor nodes act as the clients Base Station has many orders of magnitude more energy than sensor nodes Base station makes all the decisions like establishing, selecting and maintaining routing paths thus increasing the lifetime of the sensor networks Base station maintains energy levels of all sensor nodes and selects routes based on it, thus ensuring that there is no wide disparity in energy levels of nodes Each node doesn’t have to maintain consistent up-to-date routing information to other nodes

6. Assumptions All sensor nodes are static, i.e., mobility is not supported in SEER Energy consumption for each task is known Energy for communication and sensing are taken into consideration Energy for computation is not taken into consideration as it is significantly smaller compared to communication All nodes have same amount of energy available at the beginning of data transmission phase Each node spends same amount of energy in sending and receiving one packet

7. SEER Phases

8. Phase 1: Topology Construction For Base Station to make all routing decisions, it needs to have a sense of overall topology of the network it governs Topology construction typically takes place immediately after sensor nodes are deployed, however, sometimes it can be launched by base station any time it deems fit to compensate for significant changes made to the network There are 3 messages broadcasted in this phase: Neighbors Discovery (ND) Neighbors Collection (NC) Neighbors Collection Reply (NCR) ND is used for sensor nodes to know and store its neighbors information for future phases NC is used to notify nodes to send its neighbors collection information to Base Station. Also it helps nodes that recognize neighbors that were not collected during ND NCR is reply to NC message by each individual node to Base Station

9. Topology Construction (contd.) Base Station broadcasts a ND message to whole network to initiate the topology construction phase Each node does the following on receiving ND message: Record the address of node (prev_hop) from which it received and stores it in neighbors_listin ascending order of received time Change the address in prev_hopto it’s address Check if the message was received by searching pkt_seq_num in table received_pkts. If already received, then ignore the message or else store the sequence number in the table and rebroadcast to its neighbors Base Station waits for a short time and then broadcasts another message NC Each nodes follows the same steps done in ND on receiving NC message and one additional thing: Broadcast NCR message after a random delay NCR is the reply to NC broadcast of base station

10. Topology Construction (contd.) Each NCR message consists of : Address of node List of the node’s neighbors Each node upon receiving NCR follows the same steps done on receiving ND message: Check if address of the node in the message is in it’s neighbor’s list(if not update list) Change address in message to it’s address Check if broadcast message has already been received by it(if yes drop it and if no then record the packet sequence number and rebroadcast to its neighbors) Now that the Base Station has received all the information from all nodes, it has a vision of topology of the network Base Station constructs a weighted directed graph Weight of an edge in the graph is basically the available energy in the head node

11. Topology Construction (contd.)

12. Topology Construction (contd.) Calculation of weight is based on formula: Weight – Total power each node has / power for transmitting or receiving one packet Lets say, energy for sending one bit of data is 0.01 mW. In simulation conducted by the authors, size of each packet is 128 bytes ~= 1000 bits. Thus energy for sending one packet is 1000 * 0.01 = 10 mW Authors assume that each node initially has energy of 5000 mW, thus Weight for each node is 5000 mW/10 mW = 500 Neighborhood matrix is used to represent neighborhood relations between nodes

13. Phase 2:Data Transmission In SEER, Data transmission is requested by Base Station Data transmission follows the below steps: Base Station broadcasts Data Enquiry (DE) packet Sensor nodes that satisfy DE reply with a Data Enquiry Reply (DER) packet Sensor nodes that do not satisfy DE, rebroadcast packet Base Station calculates shortest path to the desired node( path from source to sink in which total energy consumed on each node along the path to send one packet is least) Shortest path is calculated based on modified version of Breadth First Search (BFS) algorithm In SEER, base station doesn’t necessarily select the absolute shortest path, it also takes into consideration the energy left in each node along that path and then selects the path When there are multiple shortest paths, path with maximal available power is chosen

14. Data Transmission (contd.) Each node receiving DE message does the following: Check if it satisfies DE If it does, reply with DER message by setting next_hopto first node in it’s neighbor’s list and prev_hopto it’s address As neighbor’s list in each node is stored in ascending order of received time of ND and NC messages, first few nodes in this list are bound to be one hop closer to base station than the node itself If it doesn’t satisfy DE, then rebroadcast DE to its neighbors by saving packet sequence number to avoid broadcasting more than once

15. Data transmission (contd.) All possible paths from Base Station to Node 4 are listed Modified BFS finds paths 1 and 6 (least energy consumed to transmit data) Even though other paths 2 to 5 have more energy than 1 and 6, SEER doesn’t use them as all of them include nodes that are present in 1 and 6 and an additional node. Thus paths 2 to 5 are not energy efficient. If nodes along path 1 have less energy than required, then BFS is run again to find another path After finding the path, base station sends a Route Reply (RR) packet to Node 4(DER initiator) using the selected path Each node on the path forwards RR until it reaches source node(Node 4) Once Node 4 receives RR(it now knows path on which to communicate with Base Station), it responds with an ACK If Base Station doesn’t receive ACK within a predefined time, it removes selected route and runs BFS again to find another path

16. Phase 3: Route Maintenance SEER uses MULTIPATH route It distributes communication load between source and destination across multiple routes thus avoiding using up energy along one path Base Station decreases the available energy in each node along the path by one after each transmission

17. Security in SEER

18. Security in SEER Generally, most attacks against sensor network routing protocols can be prevented by simple link layer encryption and authentication In SEER it is achieved in a unique way of selecting the routing path between the source and sink node, i.e, the path is selected by base station rather than the source or sink node selecting the path This helps SEER in defending specific attacks on routing protocols that attract traffic by advertising high quality routes to the base station

19. Security in SEER (contd.) Defending against wormhole and sinkhole attacks Both the attacks try to lure traffic from the sensor nodes to the base station through malicious nodes In SEER the routing path is selected by the base station and not the source or the sink. The base station periodically re-selects a new path according to current energy levels due to which adversity advertises has no impact Even if a malicious node happens to be on routing path, the attack only lasts a limited time Defending selective forwarding attacks When malicious nodes refuse to forward all or parts of the messages and drops them so they are not propagated further, then it is termed as selective forwarding attacks This type of attack is effective when the malicious node is included in the routing path. As SEER routing path selection is done uniquely at the base station and also includes a sequence number that uniquely identifies each packet. If a compromised node selectively drops packet then it will be detected in the next hop and the path would be changed.

20. Performance Evaluation

21. Performance Evaluation The proposed protocol is dynamically simulated using NS-2 for performance Setup: Rectangular area of 150mx150m where wireless sensors nodes are deployed 5 different sensor field from 30 to 130 nodes increment of 20 nodes For each network size, results averaged over 5 different sensor field All nodes assumed to be static, with 100,000 mW initial energy Transmission range is 10m Base station requests the data by broadcasting interests of a data, then the nodes that match this interest send the data to base station Each node matched sends 500 packets to base station and then the base station broadcasts another interest once it receives all the packets In this simulation, base station sends 10 interests in all

22. Performance Evaluation (contd.) • Comparison of SEER protocol with Direct Diffusion protocol in terms of : • Network throughput • Control overhead • Network lifetime • Each metric is then compared under two conditions: • Normal conditions • With 20% malicious nodes • In this slide we see comparison under normal conditions

23. Performance Evaluation (contd.) Graph (a) shows that both SEER and Directed Diffusion have high data delivery ratio and both ratios increase as the number of nodes increase Graph (b) is the comparison of the control overhead. In SEER both base station and sensor nodes need to flood control packets through the whole network. This in general works better as the node density increases Graph (c) shows the significant performance difference when compared to Directed Diffusion protocol. As SEER increases the network life time about 35% when compared to Directed Diffusion

24. Performance Evaluation (contd.) Comparison of network performance between SEER and Directed Diffusion with 20% of nodes are misbehaving

25. Performance Evaluation (contd.) Graph (a) shows that the network throughput does not experience an obvious decrease in both the protocols. When malicious nodes are on the path then SEER can detect them and then the base station selects a different path Graph (b) shows the control overhead. The over head for SEER increases from 16% to 19% as for Directed Diffusion, it increases from 19% to 27% which is quite a big jump compared to the increase in SEER As when a malicious node is detected, SEER just chooses an alternative path due to which it does not require addition overhead In graph (c) we see both protocols suffering a significant decrease, this is down to selecting a new path when malicious nodes are detected and the communication load spreads among a small number of available paths. Even then the SEER lifetime is 37% longer than Directed Diffusion as SEER distributes load more evenly

26. Conclusion The authors propose an efficient routing protocol called SEER for wireless sensor networks which utilizes multipath concept. SEER provides the following advantages: Mitigating the load of sensor nodes by transferring it to base station Extending the life time of the network Reducing the transmission delay through using shortest and reliable path Resistant to attacks that molest sensor networks by advertising high quality to Base Station

27. Reference Nidal Nasser and Yunfeng Chen, "Secure Multipath Routing Protocol for Wi reless Sensor Networks", ICDCSW'07

28. THANK YOU