Security for Ad Hoc Networks Hang Zhao 1

Security for Ad Hoc Networks Hang Zhao 1

Ad Hoc Networks Ad hoc -- a Latin phrase which means "for this [purpose]". An autonomous system of mobile hosts connected by wireless links, often called Mobile Ad hoc NETworks (MANETs) 2

Characteristics No fixed infrastructure Dynamic changing topology – Mobile devices join/leave the network unexpectedly; they can also move freely Energy-constrained Limited bandwidth Each node also serves as router – Help to relay packets received from neighbors Interoperation with the Internet 3

Comparison MANETs vs. Wired networks – In MANETs, each node also works as router for forwarding packets – In wired networks, routers perform routing task MANETs vs. Managed wireless networks – No infrastructure in MANETs – Special node known as access point (AP) in managed wireless networks 4

A MANET Example 5 http://www.comp.nus.edu.sg/ xuemingq/research.html

Mobile Devices Laptop computers Pagers, cellular phones, PDAs In-car navigators -Dash Express – Dash units talk to each other and form a network that connects to the Internet – Traffic speed data is sent back to the company, then broadcast back to all local dash units Sensors 6

Wireless Sensor Network (WSN) An emerging application area for MANETs A collection of cheap to manufacture, stationary, tiny sensors Network lifetime -- power as a major driving issue Battlefield surveillance, environment monitoring, health care, etc. 7

WSN Example 8 http://www.alicosystems.com/wireless%20sensor.htm

Other MANETs applications Collaborative work Crisis-management applications Personal Area Networking (PAN) 9

Security Requirements in MANETs Availability Authorization and Key Management Data Confidentiality Data Integrity Non-repudiation 10

Security Solution Constraints Lightweight Decentralized Reactive Fault-tolerant 11

Challenges No infrastructure Peer-to-peer architecture with multi-hop routing Mobile device physical vulnerability Stringent resource constraints Wireless medium Node mobility 12

Security Issues QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. 13 H Yang, H Y. Luo, F Ye, S W. Lu, and L Zhang, “Security in mobile ad hoc networks: Challenges and solutions” (2004). IEEE Wireless Communications.

Threats Attacks – – – – External attacks Internal attacks Passive attacks Active attacks Misbehavior 14

MANETs Security Routing security Data forwarding security Link layer security Key management Intrusion detection systems (IDSs) 15

Routing in MANETs Nodes’ mobility -topology changes rapidly Large network size -significant amount of network control traffic 16

MANET Routing Protocols Topology-based approaches – Proactive routing (table driven) – Reactive routing (on demand) – Hybrid routing Position-based approaches 17

Comparison Proactive routing – Classic routing strategies: link state, distance vector – Keep track of routes to all possible destinations – Changes in link connection updated periodically – Minimal delay but substantial fraction of control information – E.g. DSDV, WRP, TBRPF, OLSR, etc. 18

Comparison Reactive routing – Only discover routes to destinations on-demand – Consume much less bandwidth but experience substantial delay – E.g. DSR, ADOV, TORA, etc. 19

DSR vs. AODV Dynamic source routing (DSR) – Source broadcasts RREQ through the network – Intermediate nodes add its addr to RREQ and continue broadcasting until RREP received – Full path chosen by source and put into each packet sent Ad hoc on-demand distance vector (AOVD) – – – – – Hop-by-hop routing Source sends RREQ to neighbors Each neighbor does so until reach the destination Destination node sends RREP follow the reverse path Source doesn’t put whole path but only next hop addr in outgoing packets 20

Routing Protocol Attacks Attacks using modification – Redirection by modifying route sequence number – Redirection by modifying hop count – Source route modification – Tunneling QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. D. Djenouri, L. Khelladi and A.N. Badache. “A Survey of Security Issues in 21 Mobile

Routing Protocol Attacks Attacks using fabrication – Falsifying route errors – Broadcast falsified routes Spoofing attacks Rushing attacks 22

Solutions to Secure Routing Protocols QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. D. Djenouri, L. Khelladi and A.N. Badache. “A Survey of Security Issues in 23 Mobile

Data Forwarding Security Threats – Eavesdropping (passive attacks) cryptography can help to prevent but how to detect eavesdropping is still an open research topic – Dropping data packets (similar to selfishness) – Selfish behavior on data forwarding Drops other nodes’ packets to preserve its resources, e.g. battery power 24

Detection Solution against Selfishness End-to-end feedbacks Monitoring in promiscuous mode (watchdog) Activity-based overhearing Mutually according admission in neighborhood Reputation based solution Probing 25

Preventive Solution against Selfishness Nuglets – Nodes who use the service must pay for it to nodes that provide the service Data dispersal – Adding redundancy to the messages to send; thus partial reception can lead to successful reconstruction of messages 26

Link Layer Security IEEE 802.11 MAC – Vulnerable to DoS attacks – Attacks can exploit its binary exponential backoff scheme to launch DoS – A security extension to 802.11 was proposed Backoff time at the sender is provided by the receiver IEEE 802.11 WEP -discussed in wireless security 27

Key Management Most of the solutions for secure routing and data forwarding rely on cryptography Key management is problematic because of the lack of any central infrastructure – Private key infrastructure – Public key infrastructure 28

Private Key Infrastructure QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. D. Djenouri, L. Khelladi and A.N. Badache. “A Survey of Security Issues in 29 Mobile

Public Key Infrastructure QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. D. Djenouri, L. Khelladi and A.N. Badache. “A Survey of Security Issues in 30 Mobile

Intrusion Detection Systems (IDSs) Proactive solutions cannot eliminate attacks (secure routing layer, link layer mechanism) IDS presents a second wall of defense Assumptions – User and programs are observable – Normal and intrusion activities can be distinguished 31

Problems with Traditional IDSs in MANETs Infrastructureless nature of MANETs – No traffic concentration points for monitoring Resource limitation of mobile devices Lack of clear separation between normalcy and anomaly – as nodes move around, the topology changes; – so each node should expect different traffic pattern from its neighbors 32

Proposed Solutions Distributed, host-based, anomalybased, and cooperative QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. D. Djenouri, L. Khelladi and A.N. Badache. “A Survey of Security Issues in 33 Mobile

Wireless Sensor Network (WSN) Security Consists of thousands or millions of tiny devices: – – – – signal processing circuit, micro-controller, wireless transmitter/receiver, embedded sensor 34 http://agent.cs.dartmouth.edu/scalable/DSCN0022.JPG

More Stringent Performance Requirement More stringent performance requirement – Energy efficiency -network lifetime – Auto-organization – Scalability to a high number of nodes 35

Security Issues Key distribution and management – Scalable to a large number of sensor nodes – Remains to be unsolved Key pre-deployment Shared key discovery Path-key establishment – Alternatives Probabilistic key sharing protocols 36

More Issues Secure routing – Most routing protocols are quite simple in WSN, thus more vulnerable to attacks. Some new attacks are: Sinkhole attacks Hello flood attacks – Solutions SPINS -two building block security protocols: SNEP and µTESLA INSENS -intrusion-tolerant routing protocol 37

More Issues Secure data aggregation – Key theme in design and development of WSNs – Aggregators collect raw data, process it locally, and forward only the result to end-user – Aggregation can take in any places, and must be secured Denial of service – Jammed by adversaries: jam the entire network by broadcasting a high enough energy signal Resilience to node capture 38

Summary What we have discussed – Characteristics of MANETs, WSNs – Security issues in MANETs and WSNs MANETs is a growth area of research; the security issues in MANETs attract a lot of researchers; we’ll be definitely seeing more of these problems in near future. 39

More Readings H Yang, H Y. Luo, F Ye, S W. Lu, and L Zhang, “Security in mobile ad hoc networks: Challenges and solutions” (2004). IEEE Wireless Communications. 11 (1), pp. 38-47. D. Djenouri, L. Khelladi and A.N. Badache. “A Survey of Security Issues in Mobile Ad Hoc and Sensor Networks”, Communications Surveys & Tutorials, IEEE, Vol. 7, Issue 4, pp. 2--28, Fourth Quarter 2005. Yih-Chun Hu , Adrian Perrig, “A Survey of Secure Wireless Ad Hoc Routing”, IEEE Security and Privacy, v.2 n.3, p.28-39, May 2004 40