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Secure Routing in Wireless Sensor Networks: Attacks and Countermeasures. Chris Karlof and David Wagner. Key Contributions. Secure routing issues in WSNs Show how they are different from ad hoc networks Introduce two new classes of attacks Sinkhole attack Hello flood attack
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Secure Routing in Wireless Sensor Networks: Attacks and Countermeasures Chris Karlof and David Wagner
Key Contributions • Secure routing issues in WSNs • Show how they are different from ad hoc networks • Introduce two new classes of attacks • Sinkhole attack • Hello flood attack • Analyze security aspects of major routing protocols • Discuss countermeasures & design considerations for secure routing in WSNs
WSNs vs. Ad Hoc Networks • Multi-hop wireless communications • Ad hoc nets: communication between two arbitrary nodes • WSNs • Specialized communication patterns • Many-to-one • One-to-many • Local communication • More resource constrained • More trust needed for in-network processing, aggregation, duplicate elimination
Assumptions • Insecure radio links • Malicious nodes can collude to attack the WSN • Sensor are not tamper-resistant • Adversary can access all key material, data & code • Base station is trustworthy • Aggregation points may not be trustworthy
Threat Models • Device capability • Mote class attacker • Laptop class attacker: more energy, more powerful CPU, sensitive antenna, more radio power • Attacker type • Outside attacker: External to the network • Inside attacker: Authorized node in the WSN is compromised or malicious
Security Goals • Secure routing • Support integrity, authenticity, availability of messages in presence of attack • Data confidentiality
Potential Attacks • Attacks on general WSN routing • Attacks on specific WSN protocols
Attacks on General WSN Routing Protocols • Spoof, alter, or replay routing info. • Create loops, attack or repel network traffic, partition the network, attract or repel network traffic, etc. • Selective forwarding • Malicious node selectively drops incoming packets
Sinkhole attacks • Specific to WSNs • All packets are directed to base station • A malicious node advertises a high quality link to the base station to attract a lot of packets • Enable other attacks, e.g., selective forwarding or wormhole attack
Sybil attack • A single node presents multiple ID’s to other nodes • Affect geographic routing, distributed storage, multi-path routing, topology maintenance • Wormholes • Two colluding nodes • A node at one end of the wormhole advertises high quality link to the base station • Another node at the other end receives the attracted packets
Hello flood attack • Specific to WSNs • In some protocols, nodes have to periodically broadcast “hello” to advertise themselves • Not authenticated! • Laptop-class attacker can convince it’s a neighbor of distant nodes by sending high power hello messages • Acknowledge spoofing • Adversary spoofs ACKs to convince the sender a weak/dead link support good link quality
Attacks on Specific Routing Protocols • TinyOS beaconing • Construct a BFS rooted at the base station • Beacons are not authenticated! • Adversary can take over the whole WSN by broadcasting beacons
Directed diffusion • Replay interest • Selective forwarding & data tampering • Geographic routing • Adversary false, possibly multiple, location info. • Create routing loop • GEAR considers energy in addition to location • Laptop-class attacker can exploit it
Countermeasures • Shared key & link layer encryption • Prevent outsider attacks, e.g., Sybil attacks, selective forwarding, ACK spoofing • Cannot handle insider attacks • Wormhole, Hello flood, TinyOS beaconing • Sybil attack • Every node shares a unique secret key with the base station • Create pairwise shared key for msg authentication • Limit the number of neighbors for a node • Hello flood attack • Verify link bidirectionality • Doesn’t work if adversary has very sensitive radio
Wormhole, sinkhole attack • Cryptography may not help directly • Good routing protocol design • Geographic routing • Geographic routing • Location verification • Use fixed topology, e.g., grid structure • Selective forwarding • Multi-path routing • Route messages over disjoint or Braided paths • Dynamically pick next hop from a set of candidates • Measure the trustworthiness of neighbors
Authenticated broadcast • uTESLA • Base station floods blacklist • Should be authenticated • Adversaries must not be able to spoof
Conclusions • WSN security is challenging, new area of research • This paper covers security issues at network layer