On Designing Incentive-Compatible Routing and Forwarding Protocols in Wireless Ad-Hoc Networks ---- An Integrated Approach Using Game Theoretical and Cryptographic Techniques

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On Designing Incentive-Compatible Routing and
Forwarding Protocols in Wireless Ad-Hoc Networks
---- An Integrated Approach Using Game
Theoretical and Cryptographic Techniques

• Authors Sheng Zhong, Li(Erran) Li, Yanbin Grace
  Liu, Yang Richard Yang
• Published on MobiCom 2005,
• Aug. 28 - Sep.2 2005
• Presenter Xia Wang for CS610jw

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Outline

• Introduction
• Main contributions of this paper
• Ad-hoc VCG routing protocol (MobiCom03)
• Cooperation-optimal protocol design
• Evaluations
• Conclusion and future work

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Introduction

• Cooperation between nodes in wireless ad-hoc
  network can not be assumed in an environment with
  selfish nodes.
• Routing protocol has to address incentive issue
  to stimulate intermediate nodes to forward data.
• Classic game theory VCG (Vickrey-Clark-Groves)
  mechanism has been applied in network routing
  protocols. But a direct application (Ad-hoc VCG)
  has flaws.
• Ad-hoc VCG is not applicable on a lossy links.

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VCG Mechanism

• Assume each user has a private type.
• A user declares its private type to a social
  planner
• The social planner decides the outcome to
  optimize a social objective and a payment to each
  user.
• The outcome and the payment are determined in
  such a way that reporting the type truthfully is
  a dominant action and the outcome is socially
  optimal.
• Example The second-price auction

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Main contributions

• Show that no forwarding-dominant protocol exists.
• Design a cooperation-optimal protocol called
  Corsac, a Cooperation-optimal routing-and-forwardi
  ng protocol in wireless ad-hoc networks using
  cryptographic techniques.
• The protocol can be extended to a practical
  radio propagation model where packet reception
  is probabilistic.

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Ad-hoc VCG Routing Protocol(1)

• Source S V0 wants to communicate with a
  destination DVn.
• S ? (REQUEST, s0,n, 0, n, ,c0)
• Every node Vj (not S and D) receives the ROUTE
  REQUEST from a node Vi do the following
• Check whether it is a new ROUTE REQUEST
• Determine the received power
• Estimate the minimum power for Vi to reach Vj
• Replace with in the ROUTE
  REQUEST packet append its own identification j
  and the emission power.
• vj ? (REQUEST, s0,n, 0, n , ,c0, 1,
  , c1 , , j, Pemitj ,cj)

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Ad-hoc VCG Routing Protocol (2)

• Destination D
• Compute the SP and SP
• Calculate the VCG-payment for each intermediate
  node
• Where is the shortest path from S to
  D that doesnt contain node , is
  the cost.

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Ad-hoc VCG Routing Protocol (3)

• Send ROUTE REPLY with route sequence and the
  corresponding minimal required transmission power
  as well as the VCG-payment for each intermediate
  node.
• vs(j) ? vs(j-1) (REPLY, sk,0, s(1), ,
  s(k), . . . , ,,
  , Ms(1), . . . , Ms(k) )

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Ad-hoc VCG Routing Protocol(4)
An example network with edge-weight
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Ad-hoc VCG Routing Protocol(5)

• Ad-hoc VCG is claimed to be cost-efficient and
  truthful against one node cheating.
• What if more than one nodes cheat?

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Notations and definitions

• ai action of node i
• a-i action of all nodes except node i
• a (ai, a-i) action profile for all nodes
• A node is utility ui -ci pi (ci is the
  cost, pi is the payment)
• In a non-cooperative strategic game, a dominant
  action of a player is one that maximizes its
  utility no matter what actions other players
  choose. Specifically, ai is node is dominant
  action if, for any ai! ai and any a-i,
• ui(ai, a-i) ui(ai, a-i).

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Example of ad-hoc VCG fails

• Pemit 5
• R 5
• B doesnt cheat, B gets utility 0
• If B cheats by claim R 15, B gets payment 12-6
  6, its utility of 2
• Ad-hoc VCG Fail!

• Fail with more nodes cheating because of
  mutually-dependent types.

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A cooperation-optimal Protocol

• Def A routing protocol is a routing-dominant
  protocol to the routing stage if following the
  protocol is a dominant subaction of each
  potential forwarding node in the routing stage.

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A cooperation-optimal Protocol
Extensive game model Each vertex node Edge
possible decision Each subtree subgame Each
path from root to a leaf a possible set of
decision by the wireless nodes. In classic game
theory, such a path is said to be a subgame
perfect equilibrium if it is a Nash equilibrium
for every subgame
An example game tree
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A cooperation-optimal Protocol

• Def A forwarding protocol is a
  forwarding-optimal protocol to the forwarding
  stage under routing decision R if all packets are
  forwarded to their destinations in this protocol
  and following the protocol is a subgame perfect
  equilibrium under routing decision R in the
  forwarding stage.

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A cooperation-optimal Protocol

• This routing protocol addresses two components
• routing stage determines a packet forwarding
  path from a source to a destination
• Forwarding stage is to verify that forwarding
  does happen.

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Routing Stage

• Source nodes test signals
• Source S starts a session of M packets.
• divides the packets into blocks, where b
  is the number of packets in a block.
• S picks a random number r0.
• Let H be a cryptographic hash function. S
  computes
• r

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Routing Stage

• For each power level l ? P (in increasing order),
  S sends out
• (TESTSIGNAL, S, D, r, S, hl) at power level
  l, where
• r is a random number used to distinguish
  different session with source S and destination
  D.
• hl contains an encryption of S,D, r, l, aS
  using key kS,D and a MAC of the encryption using
  the same key.
• kS,D is a shared key between S and D using
  Diffie-Hellman key exchange in cryptography.
• aS is a cost-of-energy parameter representing the
  cost of unit energy at node i. (In ad-hoc VCG, it
  is ci)

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Routing Stage

• Upon receiving (TESTSIGNAL, S, D, r, P, h)
  from an upstream neighbor P, an intermediate node
  i does the following
• Node i sends out (ROUTEINFO, S, D, r, P, i,
  h) at power level Pctr (where Pctr is a power
  level for control messages such that the
  communication graph is connected when all links
  use power level Pctr for transmission).
• h is computed by encrypting h using key ki,D. For
  integrity, this message is protected by a MAC
  using key ki,D.
• If the TESTSIGNAL is the first one i receives for
  session (S, D, r), then for each l ? P (in
  increasing order), node i sends out (TESTSIGNAL,
  S, D, r, i, hl) at power level l, where hl
  contains an encryption of S,D, r, l, ai using
  the key ki,D and a MAC of the encryption using
  the same key.

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Routing Stage

• Upon receiving (ROUTEINFO, S, D, r, P, i, h),
  an intermediate node j does the following
• If this ROUTEINFO is new to node j, then node j
  sends out
• (ROUTEINFO, S, D, r, P, i, h) at power level
  Pctr

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Routing Stage

• Destination D maintains cost matrix for each
  session (S, D, r).
• Upon receiving (TESTSIGNAL, S, D, r, h) from
  neighbor P, D decrypts h, verifies the MAC using
  the key kP,D, and translates h to the
  corresponding power level l and cost-of-energy
  parameter aP . D records (l, aP ) in the cost
  matrixs entry for link (P,D).
• Upon receiving (ROUTEINFO, S, D, r, P, i, h),
  D decrypts h, verifies the packets MAC using key
  ki,D, and translates h to the corresponding
  power level l and cost-of-energy parameter aP . D
  records (l, aP ) in the cost matrixs entry for
  link (P, i).

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Routing Stage

• After collection all link cost information, D
  check, for each link, that the cost-of-energy
  parameter does not change.
• Computes LCP(S, D) and the unit payment for each
  intermediate node i.

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Packet forwarding stage

• After the routing discovery phase, the
  destination D sends the routing decision
• (S,D, r, LCP(S,D), PS,(Pi, pi) i is an
  intermediate node on LCP(S,D)) with digital
  signature along the reverse path of LCP.
• Pi is the power level for node i
• pi is the payment for node i

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Packet forwarding stage

• The source node sends out packets in block.
  Together with the last data packet in the m-th
  block, the source sends out
• For each block, the intermediate node waits for a
  confirmation after it forwards the block and
  before it start sending the next block.
• The destination decrypts all packets in a block,
  it decrypts , and sends it back along
  LCP(S, D) as a confirmation.
• Each intermediate node verifies that
• r

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Evaluations

• Simulation using GloMoSim Simulation package.
• The scenario consists of 30 nodes that are
  randomly distributed in an area of 2000 by 2000
  meters.
• Each node has transmission power level at 7 and
  14dBm.
• is set to 1 for every node

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Topology of simulation setup
A network with 30 nodes. The IDs of the nodes
are labeled. A link between two nodes indicates
that they are neighbors. The credit balance and
forwarding energy cost at the end of 15 minutes
are represented by the sizes of the circles.
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Evaluation Results
the credit balance of the nodes (the total credit
received by forwarding others traffic minus the
total credit paid in order to send ones own
traffic)
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Evaluation Results (2)
forwarding energy cost
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Effects of Cheating
Credit balance for node 3 with four different
settings After 30 minutes simulation
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Effects of Cheating(2)
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Conclusion and Future work

• Conclusion
• Design the first incentive-compatible, integrated
  routing and forwarding protocol in wireless
  ad-hoc networks.
• Combine incentive mechanisms and security
  techniques to address link cost issue.
• Future work
• This method can be extended to congestion price
  in network with limited capacity.
• A general model to integrate incentive issue in
  different layers MAC layer and application layer.

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Question?