Secure Sensor Routing A Clean-Slate Approach

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Secure Sensor RoutingA Clean-Slate Approach

• Bryan Parno, Mark Luk, Evan Gaustad, Adrian
  Perrig
• Carnegie Mellon University

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Sensor Networks

• Thousands of nodes, each with
• A CPU and 10 KB of RAM
• A radio
• Sensors (e.g., heat, motion, sound)
• Limited power
• Communicate via multi-hop routing
• Applications burglar alarms, emergency response,
  industrial uses
• All require secure routing!

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Attacks on Routing

• Inject incorrect routing information or alter
  setup/update messages
• Compromise sensors
• Provide malicious routing data/messages
• Suppress (selectively) routing messages
• Specific attacks
• Blackhole
• Wormhole
• Replication
• Denial of Service

• Sybil
• Rushing
• Slander
• Framing

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Consequences of Routing Attacks

• Controlling routing allows the attacker to
  control the networks communication
• Can view, modify, and/or drop messages
• Create loops to exhaust legitimate nodes
• Prevent or subvert proper network functionality

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Techniques for Secure Routing

• Prevention
• Harden protocols by restricting participants
  actions
• Typically employs cryptography
• Only forestalls known attacks
• Detection Recovery
• Monitor behavior for malicious activity
• Eliminate malicious participants
• Must be able to distinguish anomalous behavior
  and accurately assign blame
• Resilience
• Maintain availability even under unpredicted
  attacks
• Provide graceful performance degradation

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Previous Work

• Sensor routing
• Most assume trusted environment
• INSENS only applicable to certain topologies
• SIGF requires GPS
• Other secure routing protocols
• Typically rely on a single technique
• Prevention S-BGP, Ariadne
• Detection Recovery Watchdog, Pathrater, Secure
  Traceroute
• Resilience INSENS
• Inappropriate for resource-constrained sensor
  nodes
• Require PKI or excessive amounts of memory,
  computation or communication

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Goals

• Start from a clean-slate
• Incorporate all three security techniques
• Prevention, detection recovery, and resilience
• Provide highly secure, highly available
  point-to-point routing
• Necessary in many applications, e.g., Geographic
  Hash Tables (GHTs), key establishment, etc.
• Minimize resource utilization

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Outline

• Introduction
• Overview and Assumptions
• Address and Routing Setup
• Forwarding
• Detection and Recovery
• Simulation and Implementation

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Our Routing Protocol Architecture

• Establish routing tables and network addresses
• Use prevention techniques to thwart active
  attackers
• Detect and recover from attempts to deviate from
  the protocol or to launch additional attacks
• Apply resilient routing techniques to forward
  packets
• Uses the securely established routing tables and
  network addresses

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Assumptions

• Network authority (NA) uses a public/private
  keypair KNA , K-1NA
• Each sensor node preloaded with
• Network authoritys public key KNA
• Unique IDx
• Certificate Sig(K-1NA, IDx)
• Signature scheme optimizes for verification
• Intended for networks of primarily stationary
  sensors

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Outline

• Introduction
• Overview and Assumptions
• Address and Routing Setup
• Forwarding
• Detection and Recovery
• Simulation and Implementation

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Address and Route Setup Overview
Node Routing ID Address
Table A 0.1 B 0.0 C 1.1
D 1.0

• Goal
• Assign a unique network address to each node
• Populate each nodes routing table
• Accomplished with a recursive grouping algorithm
• Initially, each sensor constitutes its own group
• Groups repeatedly merge until all nodes belong to
  same group
• Each time a nodes group merges, the node adds
  one bit to its network address and one entry to
  its routing table

Node ID Address Routing Table
A 0.1 RTA
B 0.0 RTB
C 1.1 RTC
D 1.0 RTD
Node ID Address Routing Table
A 0.1
B 0.0
C 1.1
D 1.0
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Recursive Grouping Algorithm

• Groups act in an asynchronous, distributed
  fashion
• Each group
• Collects information about its neighbors
• Proposes to merge with smallest neighboring group
• Based on number of nodes in the group
• Ties broken based on group ID
• This metric keeps addresses and routing tables
  small
• Mutual proposal triggers merge
• Entire process is deterministic for a given
  topology
• Limits the damage an attacker can inflict

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Recursive Grouping Example
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Calculating Network Addresses

• Assume G and G decide to merge
• Each node in G independently extends its network
  address by one bit based on
• Nodes in G make similar changes

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Network Addresses Formation
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Populating Routing Tables

• Assume G and G decide to merge
• Each node in G records the neighbor from whom it
  heard about G in its current routing table slot

D
Prefix Next Hop
0. C
1.0 C
G
G
G
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Sample Routing Table
1.1.0
Prefix Next Hop
0. 0.1.1
1.0. 1.0.1
1.1.1 1.1.1
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Outline

• Introduction
• Overview and Assumptions
• Address and Routing Setup
• Forwarding
• Detection and Recovery
• Simulation and Implementation

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Forwarding

• Basic forwarding similar to area-style forwarding
• Given a destination network address route towards
  node with longest matching prefix
• Path length in logical hops bound by log(n)
• A logical hop may require several physical hops

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Forwarding Example
Message from 1.1.0 to 0.0.0
1.1.0
0.1.1
0.0.1
1.1.0
Prefix Next Hop
0. 0.1.1
1.0. 1.0.1
1.1.1 1.1.1
Prefix Next Hop
1. 1.1.0
0.0. 0.0.1
0.1.0 0.1.0
Prefix Next Hop
1. 1.0.0
0.1. 0.1.0
0.0.0 0.0.0
Prefix Next Hop
0. 0.1.1
1.0. 1.0.1
1.1.1 1.1.1
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Outline

• Introduction
• Overview and Assumptions
• Address and Routing Setup
• Forwarding
• Detection and Recovery
• Threats
• Detecting Grouping Deviations
• Eliminating Malicious Nodes
• Simulation and Implementation

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Threats

• Compromised nodes may lie about group size or ID
  to subvert route setup
• Compromised nodes may claim multiple IDs or try
  to simultaneously group with several other nodes

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Detecting Grouping Deviations

• Maintain a Grouping Verification Tree (GVT) for
  each group during recursive grouping
• Prevents attacker from lying about group ID or
  size
• Based on a hash tree construction
• Before two groups merge, they verify each others
  GVT
• Integrity of the GVTs insures integrity of the
  recursive grouping algorithm
• Final GVT covers all nodes in the network
• Can be used to authenticate any nodes network
  address

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Background Hash Trees

• Employ a one-way hash function H
  0,1?0,1?to create one-way data structures
• The Merkle Tree is one such data structure
• Each internal node calculated as
• Parent H(ChildL ChildR)
• Authenticates a leaf node given the root value
  and nodes along the path to the root

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Group ID Computation

• Assume G and G decide to merge
• Each node in G independently calculates the new
  group ID as

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GVT Formation

• One GVT per group
• GVT leaves are IDs of nodes in the group
• Internal nodes represent intermediate group IDs
• Each node maintains information about its branch
  of the GVT
• Specifically, the group ID and size of each merge
  partner

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GVT Verification

• Before merging, group G verifies the GVT for G
  (and vice versa)
• G announces its group ID (and size)
• Group G sends a challenge value to G
• The challenge uniquely selects a node in G
• Chosen node sends its certificate and GVT
  information to G
• Nodes in G verify the GVT values

Responder
Challenger
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Eliminating Malicious Nodes

• Legitimate nodes use the Honeybee mechanism to
  eliminate malicious nodes
• To revoke malicious node M, legitimate node L
  broadcasts
• IDL, IDM, and a signature
• Legitimate nodes revoke M and L
• Prevents a compromised node from revoking more
  than one legitimate node

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Outline

• Introduction
• Overview and Assumptions
• Address and Routing Setup
• Forwarding
• Detection and Recovery
• Simulation and Implementation

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Simulations

• Comparison against Beacon Vector Routing (BVR)
  protocol NSDI 2005
• Optimized for efficiency
• No security included
• Experimental Setup
• 500 nodes, random deployment, DOI radio model
• Summary of Results
• Our routing success rate 100
• Paths longer than shortest path
• Distributes overhead evenly throughout network
• Better than BVR, even in topologies with voids

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Metric Path Stretch

• Stretch Protocol Path Length / Optimal Path
  Length
• Optimistic for BVR does not include failed BVR
  routes

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Metric Load Distribution - Uniform
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Metric Load Distribution - Irregular
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Implementation

• Developed in NesC on TinyOS using Telos sensor
  nodes
• Source code to be available soon
• Challenges overcome
• Reliable Broadcast
• Asynchronicity
• Asymmetric Links
• Ongoing work to expand the current testbed

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Other Contributions

• Techniques for resilient forwarding
• Duplicate detection
• Proofs of performance and correctness
• Implementation details

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Conclusions

• Secure sensor routing is an important and
  difficult problem
• Most previous techniques assume a trusted
  environment or use a single security technique
• We design a protocol incorporating all three
  security techniques that still compares favorably
  to insecure protocols

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Thank you!
parno_at_cmu.edu
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Drawbacks of Wired Networks

• Expensive to deploy
• Expensive to maintain
• Upgrade
• Replace
• Wires can introduce failures
• Wires are costly

• Wireless networks are more cost effective!

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Merging Two Groups

• Assume G and G decide to merge
• Each node in G independently
• Calculates the new group ID
• Extends its network address by one bit according
  to
• Records the neighbor from whom it heard about G
  in the current routing table slot

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Duplicate Detection

• After recursive grouping concludes, each node
  announces its ID and network address to its
  neighbors
• Run a replication detection algorithm
  PaPeGl2005 to identify duplicates
• Detects nodes that
• Claim multiple IDs
• Simultaneously group with several other nodes
• Duplicates are revoked

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Resilient Forwarding

• Extend routing tables to facilitate multi-path
  forwarding
• During each merge, a node remembers multiple
  neighbors that announced the merge target
• Leverages natural redundancy in the recursive
  grouping algorithm

B
Prefix Next Hop0 Next Hop1
1. A C
0.1. C D
0.0.0 A --
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Resilient Forwarding

• Sender includes a direction string ? in its
  packet
• ? ?0 ?1 ?k , ?i ? 0,1
• Forwarding node selects among next hops based on
  current value of ?

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GVT Verification

• Before merging, group G verifies the GVT for G
  (and vice versa)
• G announces its group ID and size
• Group G chooses a challenger node
• Challenger creates challenge
• Challenger broadcasts the challenge to G and G
• Based on challenge, G chooses responder node
• Responder sends its certificate and GVT branch
  information to G
• Nodes in G verify the GVT values