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Toward Resilient Security in Wireless Sensor Networks. Hao Yang, Fan Ye, Yuan Yuan, Songwu Lu, William Arbaugh (UCLA, IBM, U. Maryland) MobiHoc 2005. Outline. Introduction and Background On resiliency of existing solutions LBRS Design Analysis and Simulation Results - PowerPoint PPT Presentation
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Hao Yang, Fan Ye, Yuan Yuan, Songwu Lu, William Arbaugh
(UCLA, IBM, U. Maryland)MobiHoc 2005
Toward Resilient Security in Wireless Sensor Networks.
Outline
Introduction and Background On resiliency of existing solutions LBRS Design Analysis and Simulation Results Discussions and Conclusions
Introduction
Target problems: Compromised nodes inside attacks Report fabric
ation attacks The compromised nodes forge nonexistent events that
cause both false alarms and resource waste
Existing solution and their problem Multiple parties endorse an legitimate event; en-route fi
ltering. Problem: Threshold breaks down.
Proposed approach: use location-based information to achieve resilience.
Assumptions
A Large scale sensor network that monitors a vast geographic terrain.
Size and shape of the terrain are known a priori
Sensor nodes are uniformly and randomly deployed in the terrain.
Once deployed, each node can obtain its geographic location via a localization scheme.
One resourceful sink with high survivability. Sink knows all keys
General En-route Filtering Framework
A node stores a set of symmetric keys. it uses one key to generate a Message Authentication Code (MAC) attached to an event report. It also uses its keys to verify the report forwarded to it. Each key has a unique index.
Set of symmetric keys: k1, k2, k3…
General En-route Filtering Framework
On event occurrence: A legitimate report must carry m distinct MACs. Multiple nodes sense the event and
collaboratively generate (one or more) reports with m MACs.
Report | index3 | MAC3
Report | index1 | MAC1
Report | index5 | MAC5
Report | index2 | MAC2
Report | index4 | MAC4
Report | index6 | MAC6
| index1 | MAC1Report | index3 | MAC3 | index4 | MAC4
General En-route Filtering Framework
Intermediate nodes:
Received Report
Check if it has m MACs
Check if it can verify the MACs
Is the MAC valid?
Forward packetDrop
No
No
No
Yes
General En-route Filtering Framework
Sink verification: Sink knows all keys, it can verify every MAC. Sink is the final guard
Outline
Introduction and Background On resiliency of existing solutions LBRS Design Analysis and Simulation Results Discussions and Conclusions
Interleaved Hop-by-Hop Authentication (IHA) Design parameter: m Each sensing cluster contains at least m+1 n
odes and a cluster head. Along the path, two nodes that are m+1 hops
away are associated by a pair-wise key. Threshold: m.
Interleaved Hop-by-Hop Authentication (IHA)
An Application Scenario
IHA Overview
Node initialization and deployment Each node has a unique id and should establish a
pairwise key with each of its neighbors Association discovery
Each node discovers the ids of all associated nodes Report endorsement
t+1 nodes collaboratively generate a report when an event is detected
Each participating node generates two MACs, one with the key shared with the BS, and one with the key shared with its upper associated node
CH head collects all MACs and attaches them to the report, forwarding to the BS
IHA Overview
En-Route Filtering Forwarding node verifies the MAC computed
by its lower association node; if success, it removes the MAC and computed a new one with the key shared with its upper association node
Base Station Verification BS contains a unique shared key with each
sensor
Summary of IHA
IHA verifies the reports in a deterministic and hop-by-hop fashion
Two major drawbacks in resiliency The protection breaks down when more than t
nodes along the path are compromised IHA relies on deterministic key sharing, which
results in high overhead due to dynamism Higher overhead to detect association nodes No definition on key establishment
Statistical En-route Filtering (SEF)
Global key pool is divided into m partition. Each node pre-loads with a few keys randomly chose
n from a single partition SEF is probabilistic
When an event occurs, detecting nodes jointly endorse the report with m MACs, each using a key in a different partition.
SEF assigns keys to nodes in a way that any intermediate node is able to verify the report with certain probability
Threshold: attackers obtain keys from m partition.
Outline
Introduction and Background On resiliency of existing solutions LBRS Design Analysis and Simulation Results Discussions and Conclusions
Location-Based Resilient Security (LBRS)
Terrain is divided into geographic grids and each cell is bonded with L keys.
Each node stores one key for each of its sensing cells.
Each node randomly chosen a few remote cells based on location information as its verifiable cells, and store one key for each of them.
Location-Based Resilient Security (LBRS)
Location-Based Resilient Security (LBRS)
A legitimate report is jointly generated by detecting nodes, and should carries m distinct MACs.
Intermediate nodes and sink verification processes are similar to SEF and IAH.
Two more new checking: All m distinct MACs should be bonded to one cell. Location attached in the report consistent with the
location of MACs
Location-binding key generation
Location-binding key generation: The terrain is divided into geographic grids and each cell is bounded with L keys.
How to construct a grid? How to derive keys based on the location info
rmation in a computationally efficient manner?
How to construct a grid
A virtual square grid is uniquely defined by two parameters: a cell size C, and a reference point (X0,Y0) (e.g., sink location).
Denote a cell by the location of its center, (X i,Yj), such that
How to derive keys
Preload each node with: cell size C, reference (X
0,Y0), master secret KI .
Once deployed, a node first obtains its geographic location through a localization scheme.
Derives keys during bootstrapping phase with
H() that is a one-way hash function. (Xi,Yj) is the location of the cell.
Location-guided key selection
A node defines an upstream region based on location information and only forward packet for its upstream region.
After defined upstream region, for each cell in its upstream region, select it as a verifiable cell with probability
d is the node’s distance to the sink, Dmax is the max distance between network edge and sink
Location-guided key selection
How to select upstream region and accommodate node failures? Designed to work with geographic routing
protocol. Upon moderate node failures, geographic
routing protocol find a closer detoured paths . Define beam width b. Use b and d (distance to sink) to define
upstream region.
Location-guided key selection
Benefits of LBRS
Randomized multiple compromised nodes are difficult to compromise a cell (oblivious attacks).
Damage is bonded to some local cells (smart attacks).
Trade off between storage and filtering power Location-guided key selection can reduce the
keys stored on one node and still achieve reasonable filtering power.
Outline
Introduction and Background On resiliency of existing solutions Design Analysis and Simulation Results Discussions and Conclusions
Parameter settings
Analysis—Filtering Effectiveness
One node compromised, with a distance to the BS d0 BS is in the center of the circular terrion
Detection Ratio: the percentage of forged reports being detected. Should be close to one.
Filtering Position: the number of hops a forged report can traverse before being dropped.
Analysis—Filtering Effectiveness
Analysis—Key Storage Overhead
Simulation
Platform: own simulator by Parsec language 30K nodes, 5Km x 5Km field, 100m x 100m
cell. Each simulation repeated 1000 times.
Simulation—Resiliency to random node compromise (oblivious)
Compromised nodes randomly scattered. How many cells will be compromised.
Simulation—Resiliency to random node compromise
Nc = Number of compromised nodes
Simulation—Filtering Power
Kc = number of compromised keys in a cell
Simulation—Delivery Ratio
Outline
Introduction and Background On resiliency of existing solutions Design Analysis and Simulation Results Discussions and Conclusions
Discussion
Prototype implementation: could all these fit into sensor nodes??
Platform: MICA2 Code size:
9358 bytes ROM, 665 bytes RAM Execution time: 100x100 cells
Bootstrapping: 2.8 sec MAC generation and verification: 10 ms
Discussion (Cont’)
Sensor deployment: Location information is known? Location information is required?
Routing Upstream region estimation is designed to work
with geographic routing protocols. They found some non-geographic routing
protocols (Directed Diffusion, GRAB) fit well with this model.
Require future study.
Conclusions If location is a required information, embedded
keys with locations seem to be obvious. Upstream region model is a good way to reduce
the key storage and still maintain the filtering power.
They did quite a bit of analysis and simulations to verify their claims.
Security setting is based on application scenario.