Authors : Chris Karlof, David WagnerAuthors : Chris Karlof, David Wagner

Presenter : Shan BaiPresenter : Shan Bai

Secure Routing in Secure Routing in Wireless Sensor Wireless Sensor

Networks : Attacks Networks : Attacks and Countermeasuresand Countermeasures

Presentation OutlinePresentation Outline IntroductionIntroduction BackgroundBackground Sensor Networks vs. Ad-Hoc Sensor Networks vs. Ad-Hoc

networksnetworks Problem StatementProblem Statement AttacksAttacks CountermeasuresCountermeasures

IntroductionIntroduction Propose security goals for routing in Propose security goals for routing in

wireless Sensor networkswireless Sensor networks Show how certain attacks against Show how certain attacks against

Ad-hoc networks and peer-to-peer Ad-hoc networks and peer-to-peer networks can be adapted into more networks can be adapted into more powerful attacks against sensor powerful attacks against sensor networksnetworks

Provide a list of attacks and their Provide a list of attacks and their countermeasurescountermeasures

ContributionsContributions Propose threat models and security goals for Propose threat models and security goals for

secure routing in wireless sensor networkssecure routing in wireless sensor networks Introduce TWO new classes of Attacks for Introduce TWO new classes of Attacks for

Sensor networksSensor networks SinkHole attacksSinkHole attacks HELLO flood attacksHELLO flood attacks

Show how the attacks against Ad-hoc Show how the attacks against Ad-hoc networks and peer-to-peer networks can be networks and peer-to-peer networks can be adapted into powerful attacks against adapted into powerful attacks against sensor networkssensor networks

Give a thorough security analysis of major Give a thorough security analysis of major routing protocols and energy conservation routing protocols and energy conservation topology maintenance algorithms for sensor topology maintenance algorithms for sensor networksnetworks

Discuss countermeasures and design Discuss countermeasures and design considerations for secure routing protocolsconsiderations for secure routing protocols

BackgroundBackground Sensor Network : Heterogeneous system Sensor Network : Heterogeneous system

consisting of tiny sensors and actuators consisting of tiny sensors and actuators having some computing elementshaving some computing elements

Base Station : Base Station : Point of centralized controlPoint of centralized control Gateway to another network, powerful data Gateway to another network, powerful data

processing unit, or point of human interfaceprocessing unit, or point of human interface More processing capability, memory & powerMore processing capability, memory & power

Aggregation points : Node at which the Aggregation points : Node at which the messages are processed before sending to messages are processed before sending to base stationbase station

POWER constrained environment POWER constrained environment

Sensor N/w vs. Ad-Hoc Sensor N/w vs. Ad-Hoc N/wN/w

Similarity : Support Multi-hop Similarity : Support Multi-hop networkingnetworking

Differences :Differences : Ad-hoc : Routing between any two nodesAd-hoc : Routing between any two nodes Sensor : Supports Specialized Sensor : Supports Specialized

communication patternscommunication patterns Many-to-OneMany-to-One One-to-ManyOne-to-Many Local CommunicationLocal Communication

Sensor nodes more resource constrained Sensor nodes more resource constrained than Ad-hoc nodesthan Ad-hoc nodes

Higher level of trust relationship among Higher level of trust relationship among sensor nodes sensor nodes In-network processing, In-network processing, aggregation, duplication eliminationaggregation, duplication elimination

Problem StatementProblem Statement Network AssumptionsNetwork Assumptions

Insecure Radio linksInsecure Radio links Malicious node collude to attack the Malicious node collude to attack the

systemsystem No tamper resistance on nodesNo tamper resistance on nodes Adversary can access all key material, Adversary can access all key material,

data, and code stored on the captured data, and code stored on the captured nodenode

Trust RequirementsTrust Requirements Base stations are trustworthyBase stations are trustworthy Aggregation points not necessarily Aggregation points not necessarily

trustworthytrustworthy

Problem Statement Problem Statement contd.contd.

Threat Models : 2 typesThreat Models : 2 types Based on device capabilityBased on device capability

Mote-class attacker Mote-class attacker access to few sensor access to few sensor nodesnodes

Laptop-class attacker Laptop-class attacker Access to more Access to more powerful devices. Have more battery power, powerful devices. Have more battery power, better CPU, sensitive antenna, powerful radio better CPU, sensitive antenna, powerful radio Tx, etcTx, etc

Based on attacker type / attacker locationBased on attacker type / attacker location Outside attacks Outside attacks attacker external to the attacker external to the

networknetwork Inside attacks Inside attacks Authorized node in the Authorized node in the

network is malicious/compromisednetwork is malicious/compromised

Problem Statement Problem Statement contd.contd.

Security Goals Secure routing protocol should

guarantee integrity, authenticity, availability of messages in presence of adversaries

Secrecy of application data is must

AttacksAttacks

Two Categories :Two Categories :Attacks on general sensor Attacks on general sensor

network routing network routing Attacks on specific sensor Attacks on specific sensor

network protocolsnetwork protocols

Attacks on General Attacks on General RoutingRouting

By Spoofing, Altering, or Replaying routing By Spoofing, Altering, or Replaying routing informationinformation Attacker can create loops, attract or Attacker can create loops, attract or repel network traffic, generate false message, repel network traffic, generate false message, partition network, induce delay, etcpartition network, induce delay, etc

Selective forwardingSelective forwarding Malicious node forwards Malicious node forwards only some messages, drop others. Attacker tries to only some messages, drop others. Attacker tries to be on the actual path of data flowbe on the actual path of data flow

Sinkhole AttacksSinkhole Attacks Main Reason : Specialized communication patterns Main Reason : Specialized communication patterns

supported by wsn ; All packets have same destination i.e. supported by wsn ; All packets have same destination i.e. base stationbase station

Adversary tries to attract traffic from a particular area to Adversary tries to attract traffic from a particular area to pass through a compromised node, thereby creating pass through a compromised node, thereby creating sinkhole with adversary at the centersinkhole with adversary at the center

A node may be made to look attractive to neighbors in some A node may be made to look attractive to neighbors in some routing algorithmrouting algorithm

Laptop class adversary provide a high quality route to base Laptop class adversary provide a high quality route to base station by transmitting at high power OR creating a station by transmitting at high power OR creating a wormholewormhole

Can enable other attacks e.g. selective forwardingCan enable other attacks e.g. selective forwarding

Attacks on General Routing Attacks on General Routing Contd.Contd.

Sybil AttackSybil Attack Single node presents multiple identities to other nodesSingle node presents multiple identities to other nodes Significantly affect fault-tolerance schemes like distributed Significantly affect fault-tolerance schemes like distributed

storage, multi-path routing, topology maintenancestorage, multi-path routing, topology maintenance Threat to geographical routing protocolsThreat to geographical routing protocols

WormholesWormholes do I need to explain this ? do I need to explain this ? HELLO flood attackHELLO flood attack

Some protocols require that nodes broadcast ‘hello’ Some protocols require that nodes broadcast ‘hello’ packets to advertise themselvespackets to advertise themselves

Laptop-class attacker can convince every node that it is Laptop-class attacker can convince every node that it is their neighbor by transmitting at high powertheir neighbor by transmitting at high power

Acknowledgement spoofingAcknowledgement spoofing Some routing algorithms require explicit/implicit link layer Some routing algorithms require explicit/implicit link layer

ACKsACKs Adversary can spoof ACKs for control packets and try to Adversary can spoof ACKs for control packets and try to

convince the sender that a weak link is strong or a dead convince the sender that a weak link is strong or a dead link is alive; causing packet losseslink is alive; causing packet losses

Attacks on specific Attacks on specific protocolsprotocols TinyOS beaconingTinyOS beaconing

Protocol Desc. Protocol Desc. It constructs a ‘Breadth first’ spanning tree rooted at the base It constructs a ‘Breadth first’ spanning tree rooted at the base

stationstation Base station periodically broadcast route updatesBase station periodically broadcast route updates Immediate nodes Immediate nodes parent, base station; other nodes parent, base station; other nodes

parent, from who they receive the first updateparent, from who they receive the first update Packets travel through the paths along tree Packets travel through the paths along tree

Attacks:Attacks: Unauthenticated route updates Unauthenticated route updates Malicious node acts Malicious node acts

as base stationas base station Authenticated route updates Authenticated route updates

Two colluding nodes (laptop-class attacker) form wormhole to Two colluding nodes (laptop-class attacker) form wormhole to direct all traffic through themdirect all traffic through them

Laptop-class attacker use HELLO flood attack Laptop-class attacker use HELLO flood attack every node every node marks attacker as parentmarks attacker as parent

Mote-class attacker can cause ‘Routing loops’ between two Mote-class attacker can cause ‘Routing loops’ between two nodesnodes

Attacks on specific Attacks on specific protocolsprotocols

Directed diffusionDirected diffusion Protocol desc. Protocol desc.

Data-centric routing algorithmData-centric routing algorithm Base station send the ‘named’ data which is Base station send the ‘named’ data which is

flooded as ‘interests’ throughout the flooded as ‘interests’ throughout the networknetwork

‘‘Gradients’ are set up to ‘draw’ events Gradients’ are set up to ‘draw’ events (data matching the interests)(data matching the interests)

Base station positively reinforces high data Base station positively reinforces high data rates pathsrates paths

Attacks Attacks Cloning i.e. Replay of interest by the Cloning i.e. Replay of interest by the

adversary adversary Selective forwarding and data tamperingSelective forwarding and data tampering

Attacks on specific Attacks on specific protocolsprotocols Geographic routingGeographic routing

Two protocols:Two protocols: GEAR (Geographic and Energy Aware Routing)GEAR (Geographic and Energy Aware Routing) GPSR (Greedy Perimeter Stateless Routing)GPSR (Greedy Perimeter Stateless Routing)

Leverage nodes’ positions & explicit Leverage nodes’ positions & explicit geographic packet destinations to efficiently geographic packet destinations to efficiently disseminate queries and route updatesdisseminate queries and route updates

Require exchange of location informationRequire exchange of location information AttackAttack : Location information : Location information

misrepresented misrepresented Adversary advertise wrong location info. so as to Adversary advertise wrong location info. so as to

place himself in the pathplace himself in the path Adversary forge location advertisements Adversary forge location advertisements

creating routing loopscreating routing loops In GEAR, energy is also considered In GEAR, energy is also considered adversary adversary

advertise maximum energy (Laptop class advertise maximum energy (Laptop class attacker again !!)attacker again !!)

CountermeasuresCountermeasures Secret shared key & Link layer encryptionSecret shared key & Link layer encryption

Prevents ‘Outsider attacks’ like Sybil attacks, Prevents ‘Outsider attacks’ like Sybil attacks, Selective forwarding, Sinkhole attacks, ACK Selective forwarding, Sinkhole attacks, ACK spoofingspoofing

Ineffective against ‘Insider attacks’ like Wormhole, Ineffective against ‘Insider attacks’ like Wormhole, Hello floods, TinyOS beaconingHello floods, TinyOS beaconing

Hello flood, SybilHello flood, Sybil Every node shares a unique symmetric key with Every node shares a unique symmetric key with

the base stationthe base station Then two nodes generate pair-wise shared secret Then two nodes generate pair-wise shared secret

key between them (Needham – Schroeder key between them (Needham – Schroeder symmetric key exchange) for ‘Identity verification’symmetric key exchange) for ‘Identity verification’

Limit the number of neighbors for a node Limit the number of neighbors for a node prevent adversary from establishing shared keys prevent adversary from establishing shared keys with everyonewith everyone

Wormhole, SinkHoleWormhole, SinkHole “ “No viable solutionNo viable solution” ” except ‘Good routing protocol design’ to avoid except ‘Good routing protocol design’ to avoid them e.g. Geographical Routing protocolsthem e.g. Geographical Routing protocols

Countermeasures contd.Countermeasures contd. Geographical routingGeographical routing attacksattacks Restrict the Restrict the

structure of topology to eliminate the need for structure of topology to eliminate the need for location information by the node. Use fixed location information by the node. Use fixed topology like square, triangular or Hex Grid topology like square, triangular or Hex Grid structurestructure

Selective forwardingSelective forwarding Use Multipath Use Multipath Routing; messages routed over disjoint paths Routing; messages routed over disjoint paths

Authenticated Broadcast and floodingAuthenticated Broadcast and flooding μμTESLA protocol to prevent replay of TESLA protocol to prevent replay of

broadcast messages issued by the base stationbroadcast messages issued by the base station Flood the information about the malicious Flood the information about the malicious

nodes in the networknodes in the network

ConclusionsConclusions

Paper describes …Paper describes … Too... many types of attacks! With Too... many types of attacks! With

lots of (overlapping) details….lots of (overlapping) details…. Two new types of attacks (Attn : Bad Two new types of attacks (Attn : Bad

Guys! want to try them?)Guys! want to try them?) And their countermeasures...And their countermeasures...

Over to contrarian………..Over to contrarian………..

CountermeasuresCountermeasures Outsider attacks vs. Insider attacksOutsider attacks vs. Insider attacks

The majority of outsider attacks can be prevented The majority of outsider attacks can be prevented by Secret shared key & Link layer encryption. by Secret shared key & Link layer encryption.

Prevents Sybil attacks, Selective forwarding, Sinkhole Prevents Sybil attacks, Selective forwarding, Sinkhole attacksattacks

Ineffective against Wormhole, Hello floods attacks.Ineffective against Wormhole, Hello floods attacks. Completely ineffective in the presence of insider Completely ineffective in the presence of insider

attacksattacks Bogus routing informationBogus routing information Create sinkholesCreate sinkholes Selectively forward packetsSelectively forward packets Sybil attacks Sybil attacks HELLO floodsHELLO floods

CountermeasuresCountermeasures Countermeasure to Insider SybilCountermeasure to Insider Sybil attacksattacks

Every node shares a unique symmetric key with the base Every node shares a unique symmetric key with the base stationstation

A pair of neighbor nodes use the resulting key to A pair of neighbor nodes use the resulting key to implement an authenticated, encrypted link between implement an authenticated, encrypted link between them.them.

Base station limit the number of neigbors a node is Base station limit the number of neigbors a node is allowed to have – prevent an insider attacker allowed to have – prevent an insider attacker establishing shared keys with every node in the network.establishing shared keys with every node in the network.

Not perfect Not perfect Malicious nodes can still communicating with its verified Malicious nodes can still communicating with its verified

neighborsneighbors Two or more colluding nodes may attack the network Two or more colluding nodes may attack the network

more powerfullymore powerfully

CountermeasuresCountermeasures

Countermeasure to HELLO flood attacksCountermeasure to HELLO flood attacks Verify the bidirectionality of the link between Verify the bidirectionality of the link between

two nodestwo nodes How about the adversary have highly How about the adversary have highly

sensitive receivers?sensitive receivers?

CountermeasuresCountermeasures Countermeasure to Wormhole, SinkHole Countermeasure to Wormhole, SinkHole

attacksattacks Geographical Routing protocols. Geographical Routing protocols.

Problems: How to get the location information – Problems: How to get the location information – attackers may disseminate spoofed location attackers may disseminate spoofed location informationinformation

Solution: Restrict the structure of topology to Solution: Restrict the structure of topology to eliminate the need for location information by the eliminate the need for location information by the node. Use fixed topology like square, triangular or node. Use fixed topology like square, triangular or Hex Grid structure. However, it also restrict its Hex Grid structure. However, it also restrict its application.application.

Suggestions: using multipath routing, and Suggestions: using multipath routing, and design effective evaluation methods to design effective evaluation methods to determine the quality of each routes.determine the quality of each routes.

CountermeasuresCountermeasures

Countermeasure to Selective forwardingCountermeasure to Selective forwarding Multipath routing using completely disjoint Multipath routing using completely disjoint

paths or Braided pathspaths or Braided paths Allowing nodes dynamically choose a packet’s Allowing nodes dynamically choose a packet’s

next hop from a set of possible candidates.next hop from a set of possible candidates. Not enough: add evaluation method to Not enough: add evaluation method to

discriminate different routesdiscriminate different routes

CountermeasuresCountermeasures Authenticate Broadcast and floodingAuthenticate Broadcast and flooding

Base station is trustworthy.Base station is trustworthy. Adversaries must not be able to spoof Adversaries must not be able to spoof

broadcast or flooded messages from any broadcast or flooded messages from any base station.base station.

HELLO message from neighbor nodes should HELLO message from neighbor nodes should be authenticated and impossible to spoofbe authenticated and impossible to spoof..

Attention: authentication should be Attention: authentication should be efficient – public key cryptography and efficient – public key cryptography and digital signatures is beyond the digital signatures is beyond the capabilities of sensor nodes.capabilities of sensor nodes.