18-06-2011, 10:44 AM
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Passive Keyless Entry System (PKE)
PKE systems allow drivers to enter their vehicles without any explicit action to unlock them
Ideal for vehicles for all kinds, specially family types
Consists of a vehicle and a customer identification device which serve as communication peers
LF uplink- vehicle to CID
RF link- CID to vehicle
Communication process
Components of PKE system
Vehicle
Loop antenna
Low Frequency (LF) transmitter
Radio Frequency (RF) receiver
Microcontroller
Contd…
Customer Identification Device (CID)
3 Orthogonal antennas
Low power Microcontroller unit
RF transmitter
Efficient battery usage
Operates on lithium battery
Remains in low power consuming sleep mode when not communicating with vehicle
Wakes up only when a valid base-station command with a predefined header is detected from the vehicle
Operates in an emergency back up mode in low battery conditions
Working
When the owner pulls a door handle, the vehicle transmits challenge in the form of LF interrogation signals .
CID in the range of 1-2 m wakes up from its sleep mode, it decodes the information
If the information is valid, then CID encrypts it
Cipher data is sent back to the vehicle in the form of RF signals
The vehicle also encrypts its own challenge using the same encryption key
It compares the cipher data with its with own calculated response.
If both matches, the user is allowed to access the vehicle.
ZigBee
Radio-frequency (RF) applications that require a low data rate, long battery life, and secure networking and operates at a bandwidth of 2.4 GHz.
Based on the IEEE 802.15.4-2003 standard
Can activate from sleep in 30 ms or less
Keyless Ignition System
Once inside the car, the engine can be started by simply pressing the start button.
Immobilizer prevents the engine from running unless the correct CID is present.
If CID is not present, then fuel does not get injected into the engine.
Security Threats
Dictionary Attack :
Thief builds an electronic dictionary
Valid entry (challenge, response) pair
keep pulling a door handle
Two-thief attack or Relay attack :
two thieves attempt to bridge the gap
thieves carry receiver and amplifier
May communicate at different frequencies
Solutions to two thief attack
Detecting the repeaters
Measure the loop time delay
a threshold value is already estimated
Corrupting the signals
Unidirectional LF link
Bidirectional RF link
Ensures that the thieves’ devices are always on
Continuous transmission of interrogating signals by the vehicle
Two kinds of distortion
one interrogating signal may overlap with another
no signal is transmitted
feedback signal may overlap with the interrogating signal
feedback signal is corrupted
Advantages:
High bit-rate communication via RF
Elimination of hardware needed for fast and smooth operation
Magnitude of feedback loop channel is measured
In time domain, the signals x(t) and y(t) are related as:
Causes a nonlinear distortion for the different frequency components of the transmitted pulse.
Applications
Automatic car lock
By walking over 1.5 to 2 meters away from car, doors will automatically lock and ARM the security system.
Low battery alarm
Unclosed door alarm
Contd…
PKE systems can be implemented in garage and houses
Passive Keyless Entry System (PKE)
PKE systems allow drivers to enter their vehicles without any explicit action to unlock them
Ideal for vehicles for all kinds, specially family types
Consists of a vehicle and a customer identification device which serve as communication peers
LF uplink- vehicle to CID
RF link- CID to vehicle
Communication process
Components of PKE system
Vehicle
Loop antenna
Low Frequency (LF) transmitter
Radio Frequency (RF) receiver
Microcontroller
Contd…
Customer Identification Device (CID)
3 Orthogonal antennas
Low power Microcontroller unit
RF transmitter
Efficient battery usage
Operates on lithium battery
Remains in low power consuming sleep mode when not communicating with vehicle
Wakes up only when a valid base-station command with a predefined header is detected from the vehicle
Operates in an emergency back up mode in low battery conditions
Working
When the owner pulls a door handle, the vehicle transmits challenge in the form of LF interrogation signals .
CID in the range of 1-2 m wakes up from its sleep mode, it decodes the information
If the information is valid, then CID encrypts it
Cipher data is sent back to the vehicle in the form of RF signals
The vehicle also encrypts its own challenge using the same encryption key
It compares the cipher data with its with own calculated response.
If both matches, the user is allowed to access the vehicle.
ZigBee
Radio-frequency (RF) applications that require a low data rate, long battery life, and secure networking and operates at a bandwidth of 2.4 GHz.
Based on the IEEE 802.15.4-2003 standard
Can activate from sleep in 30 ms or less
Keyless Ignition System
Once inside the car, the engine can be started by simply pressing the start button.
Immobilizer prevents the engine from running unless the correct CID is present.
If CID is not present, then fuel does not get injected into the engine.
Security Threats
Dictionary Attack :
Thief builds an electronic dictionary
Valid entry (challenge, response) pair
keep pulling a door handle
Two-thief attack or Relay attack :
two thieves attempt to bridge the gap
thieves carry receiver and amplifier
May communicate at different frequencies
Solutions to two thief attack
Detecting the repeaters
Measure the loop time delay
a threshold value is already estimated
Corrupting the signals
Unidirectional LF link
Bidirectional RF link
Ensures that the thieves’ devices are always on
Continuous transmission of interrogating signals by the vehicle
Two kinds of distortion
one interrogating signal may overlap with another
no signal is transmitted
feedback signal may overlap with the interrogating signal
feedback signal is corrupted
Advantages:
High bit-rate communication via RF
Elimination of hardware needed for fast and smooth operation
Magnitude of feedback loop channel is measured
In time domain, the signals x(t) and y(t) are related as:
Causes a nonlinear distortion for the different frequency components of the transmitted pulse.
Applications
Automatic car lock
By walking over 1.5 to 2 meters away from car, doors will automatically lock and ARM the security system.
Low battery alarm
Unclosed door alarm
Contd…
PKE systems can be implemented in garage and houses
