New Approach for Selfish Nodes Detection in Mobile Ad hoc Networks
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New Approach for Selfish Nodes Detection in Mobile Ad hoc Networks Djamel Djenouri: Basic Software Laboratory, CERIST Center of Research, Algiers, Algeria. E­mail: ddjenouri@mail.cerist.dz Nadjib Badache: Computer Science Department, USTHB University, Algiers, Algeria.

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New approach for selfish nodes detection in mobile ad hoc networks

New Approach for Selfish Nodes Detection in Mobile Ad hoc Networks

Djamel Djenouri: Basic Software Laboratory, CERIST Center of Research, Algiers, Algeria.

E­mail: ddjenouri@mail.cerist.dz

Nadjib Badache: Computer Science Department, USTHB University, Algiers, Algeria.

E­mail: badache@mail.cerist.dz

SeCQos Workshop, Athens, September 2005


Outline

Outline Networks

1 Overview on Mobile Ad hoc Networks (MANETs) 2 Selfish behavior on packet forwarding problem 3 Watchdog

4 Watchdog’s limitation

5 New Solution

6 Simulation results

7 Perspectives

8Conclusion

SeCQos Workshop, Athens, September 2005


New approach for selfish nodes detection in mobile ad hoc networks

MANET NetworksOverview (Definition)

  • A MANET is a collection of Wireless mobile hosts making on the fly a temporary network, without relying on any fixed infrastructure.

  • No central administration exists

  • Mobile hosts cooperate to ensure roles ensured by the fixed infrastructure in traditional networks

SeCQos Workshop, Athens, September 2005


New approach for selfish nodes detection in mobile ad hoc networks

MANET NetworksOverview (Multi-Hop)

SeCQos Workshop, Athens, September 2005


New approach for selfish nodes detection in mobile ad hoc networks

MANET’s features Networks

  • Dynamic Topology

  • Limited bandwidth

  • Limited physical Security

  • Infrastructurless

  • Limited energy resources

SeCQos Workshop, Athens, September 2005


Selfish behavior
Selfish behavior Networks

SeCQos Workshop, Athens, September 2005


Watchdog
Watchdog Networks

•Proposed by Marti et al. In MobiCom 2000

• Many recent sophisticated solutions rely on it in their monitoring component

SeCQos Workshop, Athens, September 2005


Watchdog s principles
Watchdog Networks’s principles

  • Based on the promiscuous mode monitoring and implemented with a source routing protocol.

  • When a node Na sends a packet to Nb to forward to Nc, it monitors it by simply overhearing the channel, it validates the forwarding iff it overhears the packet retransmitted by Nb.

  • This process is generated for each couple of hops in the route

SeCQos Workshop, Athens, September 2005


New approach for selfish nodes detection in mobile ad hoc networks

Watchdog Networks

If packet heard  OK

Else increase Nc’s failure Tally

failure Tally > threshold  the node misbehave

SeCQos Workshop, Athens, September 2005


Watchdog s detection drawbacks
Watchdog Networks’s detection drawbacks

  • Does not detect correctly and could cause false detections when the power control technique is employed

  • Does not detect selfish nodes in many cases (collisions, partial dropping, collusions)

SeCQos Workshop, Athens, September 2005



New solution two hop ack
New solution (Two-hop ACK) Networks

  • We propose a new monitoring solution based on two-hop ACK.

  • Assume A monitors B’s forwarding to C, this latter acknowledges each packet by sending a two hop ACK back to A via B.

  • An efficient asymmetric encryption strategy is used to ensure authenticity of ACKs and to prevent the following vulnerability:

SeCQos Workshop, Athens, September 2005


New solution hop ack
New solution (hop ACK) Networks

  • B misbehaves and drops packets, to circumvent A it sends it a falsified ACK on behalf of C.

  • The encryption strategy we used gets over this vulnerability and,

  • it is relatively of low cost, since it merely encrypts short random numbers, instead of compute digital signature on the packets.

SeCQos Workshop, Athens, September 2005


New solution hop ack1
New solution (hop ACK) Networks

- Decrypts r

- - Checks whether it matches the one it generates

- If so, it validates the forwarding

  • - Generates r

  • Encrypts it with C’s PK

  • Adds it to the packet

  • Decrypts r

  • Encrypts it with A’s PK

  • Adds it to a 2 hop ACK packet

SeCQos Workshop, Athens, September 2005


Simulation results
Simulation results Networks

SeCQos Workshop, Athens, September 2005


Two hop acks problem
Two-hop ACKs Problem Networks

  • The obvious problem of our first solution is the important overhead it engenders, even if the nodes well behave. It requires a two-hop ACK for each data packet, which is costly.

SeCQos Workshop, Athens, September 2005


Perspectives
Perspectives Networks

We plan to complete the proposal by

  • Reduce the overhead

  • Defining efficiently the threshold of accusasion

  • Defining actions that have to be taken when a node is accused as a selfish

  • and particulary by proposing a mechanism allowing nodes to exchange their knowledge regarding nodes that behave selfishly.

SeCQos Workshop, Athens, September 2005


Random two hop ack
Random two-hop ACK Networks

  • To overcome the two-hop cost, we suggest that A would not continuously ask an ACK, but randomlydecides whether to do so with a probability p, and maps the decision in the packet.

  • This randomization and mapping prevent B from deducing which packet includes an ACK request, and let it motivated to forward all packets

SeCQos Workshop, Athens, September 2005


Random two hop ack1
Random two-hop ACK Networks

  • P is updated according to B’s behavior, it is decreased each time B forward a packet until reaching its minimum value, and set to 1 upon a dropping detection.

  • This way, more trust is accorded to well-behaving nodes and ACK ask is enforced after a dropping, which ensure the efficiency and decreases the cost especially when selfish nodes rate is low, as shown in the simulation results

SeCQos Workshop, Athens, September 2005


Conclusion
Conclusion Networks

  • Our solution is operational regardless the power control employment

  • It reduces the false detection rate with low cost (energy and delay)

  • The random two-hop ACK reduces dramatically the overhead

SeCQos Workshop, Athens, September 2005


New approach for selfish nodes detection in mobile ad hoc networks
? Networks

SeCQos Workshop, Athens, September 2005