Secure Localization Algorithms for Wireless

Sensor Networks

proposed by A. Boukerche, H. Oliveira, E. Nakamura, and A. Loureiro (2008)

Maria Berenice Carrasco

Outline

• Motivation (from two perspectives) • Secure Localization– Overview– Known attacks– Solutions

• Location Verification• Design considerations• Conclusions

Motivation

• Applications : Data fusion– Locations and timestamps

• Other communication protocols– Routing, location-based

authentication.etc.

• Why is Localization important?– Popularity of wireless sensor networks

(WSN)• Hostile environments• Monitoring & control applications

– Military fields, monitoring of structures, etc.

– The knowledge of sensor’s locations is required by

Motivation

• Why is Security important?– Vulnerability of WSN

• Remote environments• Broadcast nature of the channel

– What an attacker can potentially do?• Physical manipulation• Jamming• Injecting code

– As a result…• Wrong results: wrong decisions

GOAL: Make the node think it is somewhere different from actual location

Secure Localization

• Goal: To guarantee correctness despite of the presence of intruders

• Network model:• Beacons: GPS or manual configuration• Common nodes: requesting

• Classification:• Range-based localization: Distance• Range-free localization: No connectivity informationo Node-centrico Infrastructure-centric: BS, CA

Relative Localization

Secure Localization

• General Process has two phases:1. Information Collection: distance/angle

measure– # of hops, RSSI, ToA, AoARange-free ignores this phase

2. Location Computation: include reference points

Triangulation

Trilateration

Secure Localization

• Known Attacks– Consider an insider Vs. an

outsider

– Reply attack• Jams the transmission• Waits (extra delay)• Replays the same packet

pretending to be the sender• Inaccurate location estimation

Secure Localization

• Known Attacks– Range-change attack

• Special case of the Replay attack• Increase/decrease range measurements

– Impersonation• Victims: mostly beacon nodes

– Sybil attack• Claims multiple identities

Secure Localization

• Known Attacks– Wormhole attack

• Tunnel• Jams packets• Replays packets through this tunnel

Secure Localization

• Solutions– Cryptography

• Against impersonation and data corruption• Use of :

– Authentication » Verify the sender

– Data integrity» Data is unchanged» Example: distance bounding (based on

SEAD)

Secure Localization

• Solutions– Cryptography (continued)

• Symmetric cryptography– Common private key – WSN are resource-constrained

• Pre-deployed keys• Functions to derive keys: Storage Complexity• Compromised nodes defeat this mechanism

Secure Localization

• Solutions– Misbehavior Detection and Block

• Against compromised nodes• Observe behavior of nodes• Detect and revoke misbehaving nodes• Some techniques

– RTT observation between two neighbors» Assumption: extra delay of a replay attack

– Reputation-based mechanism» Beacon monitors its neighborhood -> table

Secure Localization

• Solutions– Robust Position Computation

• Filter erroneous information during computation• Assumption: Good nodes > Malicious nodes• Statistical techniques

– Least Squares Method

Location Verification

• BS also learn sensors’ locations – Data Aggregation

• Must verify the location claimed is correct– Did the event really happened there?

• An approach: The Echo Protocol– Check if the node is inside the claimed region– Two types of nodes: p (prover) and v (verifier)– Consider c (speed of light) and s (speed of

sound)

Location Verification

• An approach: The Echo Protocol (continued)– Intuition (Simple Case)

• v only verifies provers inside R

• If p is able to return the packet in sufficient time, then v is sure that p is within d(v,l) meters of v

• Otherwise: p is further away or processing delay

Design Considerations

• No system is totally safe– Network model & adversary model

• Level of security Vs. Available resources– Particular application– Range-based :

• Distance bounding: HW with nanosecond precision

– Asymmetric cryptography• More robust but energy consuming

Design Considerations

• Who initiates the secure localization process?– On-demand– Periodic process

• Useful domain for an intruder– Use only beacon nodes– Use beacon nodes and also nodes with

known positions as reference points

Conclusions

• It is not feasible to use tamper-resistant hardware– Low cost of sensor nodes– Massive deployment

• Trade-off required– Accuracy demanded by the application– Available resources– Environment

• Combination of techniques is desirable