Security in Vehicular Ad hoc Networks VANETs

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Security in Vehicular Ad hoc Networks (VANETs)

• Jayanthi Rao
• CSE 825 Course presentation
• March 10, 2008

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Acknowledgements

• Presentation based on
• Maxim Raya and Jean-Pierre Hubaux, The security
  of vehicular ad hoc networks, SASN 2005.
• Bryan Parno and Adrian Perrig, Challenges in
  securing vehicular networks, SECON 2005.
• Some slides courtesy above authors.

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Presentation outline

• What is a VANET?
• VANET applications
• Adversaries
• Security threats and attacks
• Security primitives for attack prevention or
  handling strategies

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A modern vehicle
A modern vehicle is a network of
sensors/actuators on wheels !
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What is a VANET (Vehicular Ad hoc NETwork)?

• Communication typically over the Dedicated
  Short Range Communications (DSRC) (5.9 GHz)
• Example of protocol IEEE 802.11p

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Motivation for VANET

• Increase safety
• Hundreds of thousands of people are killed
  world-wide due to road accidents yearly.
• Many more are injured.
• Traffic optimization
• Congestion/traffic jams cost time and fuel.

Both these problems can be solved or mitigated
by giving timely information to the drivers!
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Differences from MANET

• Large scale potentially billion
• Fleeting contact with other vehicles
• Nodes not as constrained in terms of energy,
  storage and computation.

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VANET applications

• Safety alerts
• Requirement Bounded latency
• Primary Issue Broadcast storm
• Congestion warning
• Requirement Message persistence
• Primary Issue Disconnected network
• Infotainment
• Requirement End-to-end connectivity
• Primary Issue Disconnection due to high mobility

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Application-1 Congestion Detection

• Vehicles detect congestion when
• Vehicles gt Threshold 1
• Speed lt Threshold 2
• Relay congestion information
• Hop-by-hop message forwarding
• Other vehicles can choose alternate routes

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Application-2 Deceleration Warning

• Prevent pile-ups when a vehicle decelerates
  rapidly

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Attackers

• Insider or outsider
• Insider valid user
• Outsider Intruder, limited attack options
• Malicious or rational
• Malicious No personal benefit, intends to harm
  other users
• Rational seeks personal benefits, more
  predictable attack
• Active or passive
• Active Generates packets, participates in the
  network
• Passive Eavesdrop, track users

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Security Attacks
Goals
Execution
Actions
Congestion Creation/ avoidance
Insert bogus congestion warnings
Single
Single, multiple Entities (Sybil)
Misrepresent Location of accident
Cause accidents or pile-ups
Track individuals
Multiple
Message suppression
Aggressive insertion of messages/jamming
Denial of service
Independent
Colluding
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Security Requirements

• Authentication
• React only to legitimate events. Authenticate
  senders of messages.
• Verification of data consistency
• Legitimate senders can send false data
  (attack/unintentional). Can cause immense damage
  even fatalities.
• Availability
• Network should be available under jamming attacks
• Non-repudiation
• Drivers causing accidents should be reliably
  identified
• Privacy (conflicts with authentication)
• Privacy of drivers against unauthorized
  observers.
• Real-time constraints
• High speed means constraints on time

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Security Architecture
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Key Management

• Key distribution
• How will the key be distributed ?
• Key certification
• Who will certify the keys ?
• Key revocation
• When the key is compromised, what is the
  revocation procedure ?

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Tamper-proof device

• Each vehicle carries a tamper-proof device
• Contains the secrets of the vehicle itself
• Has its own battery
• Has its own clock (notably in order to be able to
  sign timestamps)
• Is in charge of all security operations
• Is accessible only by authorized personnel

Tamper-proof device
((( )))
Vehicle sensors (GPS, speed and acceleration,)
Transmissionsystem
On-boardCPU
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Digital signatures

• Symmetric cryptography is not suitable messages
  are standalone, large scale, non-repudiation
  requirement
• Hence each message should be signed with a DS
• Liability-related messages should be stored in
  the EDR

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VPKI (Vehicular PKI)

• Each vehicle carries in its Tamper-Proof Device
  (TPD)
• A unique and certified identity Electronic
  License Plate (ELP)
• A set of certified anonymous public/private key
  pairs
• Before a vehicle sends a safety message, it
  signs it with its private key and includes the
  CAs certificate.
• Mutual authentication can be done without
  involving a server
• Authorities (national or regional) are
  cross-certified

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The CA hierarchy two options
1. Governmental Transportation Authorities
2. Manufacturers
Manuf. 1
Manuf. 2
Car B
Car A
Car B
Car A

• The governments control certification
• Long certificate chain
• Keys should be recertified on borders to ensure
  mutual certification

• Vehicle manufacturers are trusted
• Only one certificate is needed
• Each car has to store the keys of all vehicle
  manufacturers

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Key revocation

• All cryptographic material of a vehicle is
  compromised
• CA sends revocation message to the TPD.
• A particular key is compromised
• CA sends revocation message to the TPD for each
  revoked key. High overhead.
• Short key certificate lifetimes. Large storage
  required.

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Security primitives

• Authenticated localization of message origin
• Option 1
• Beacons broadcast location with timestamp and
  signature. Include this packet in all messages.
• Requires infrastructure.
• Option 2 Use relative localization

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Security primitives Contd.

• Anonymization service
• Attempt to balance authentication and privacy
• Option 1
• Key changing algorithm that adapts to vehicle
  speed
• A large set of keys needs to be stored in the
  vehicle and periodically renewed (during regular
  vehicle maintenance visits)
• Option 2
• Drivers authenticate to a service with their
  permanent Id and receive a temporary Id that
  cannot be traced back to the driver.
• Infrastructure required.

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Security primitives Contd.

• Secure aggregation
• Vehicle count the number of vehicles it passes
  and reports the sum. Receiving vehicle
  authenticates the information and is able to
  estimate the amount of traffic ahead.

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Questions?