Relay Attacks on Passive Keyless Entry and Start Systems in Modern Cars Srdjan Čapkun (joint work with Aurélien Francillon, Boris Danev) 1
Agenda 1. Overview of Car Key Systems 2. Previous Attacks: In Practice 3. Passive Keyless Entry and Start Systems 4. Relay Attacks 5. Analysis on 10 Models 6. Conclusion 2
Modern Cars Evolution Increasing amount of electronics in cars For convenience, security and safety Entertainment Engine control Distance radar TPMS (Usenix Security 2010) Key systems On board computers and networks (S&P 2010) 3
4 Categories of Key Systems Metallic key Remote active open Immobilizer chips Passive Keyless Entry and Start (PKES) 4
Car Keys Active Remote Open Active keys: Press a button to open the car Physical key to start the car Need to be close (<100m) Shared cryptographic key between the key and the car Previous attacks: weak cryptography e.g. Keeloq (Eurocrypt 2008, Crypto 2008, Africacrypt 2009) In Microchip devices 5
Keys With Immobilizer Chips Immobilizer chips Passive RFID Authorizes to start the engine Close proximity: centimeters Are present in most cars today With metallic key With remote open Shared cryptographic key between the key and the car Previous attacks: weak cryptography e.g. Texas Instruments DST Usenix Security 2005 Security Analysis of a Cryptographically-Enabled RFID Device 6
Passive Keyless Entry and Start PKES / Smart Key Need to be close (<2m) and the car opens Need to be in the car to start the engine No need for human action on the key Allows to open and start the car 7
Agenda 1. Overview of Car Key Systems 2. Previous Attacks: In Practice 3. Passive Keyless Entry and Start Systems 4. Relay Attacks 5. Analysis on 10 Models 6. Conclusion 8
Protocol Attacks Replay/forge messages On very badly designed systems Requirements: Eavesdrop messages + ability resend them Only a few messages are sufficient No freshness check Can be reused without the presence of the car owner Allows to create a fake key to open/close/start the car Probably no more present on the market now We found one after market system vulnerable to this attack bought on the internet 9
Radio Jamming Attacks Requirements: A radio device close to the car Jams the frequency of the key system Thief/device needs to be present while the car is closed Jam the close radio message sent by the key car owner Prevents the car from closing User may notice, or not Does not allow by itself to start the car 10
Cryptographic Attacks On Active Remote Open and Immobilizer Chips Requirements: Require to eavesdrop messages exchanges Sometimes thousands of exchanges Some require physical access to the key Allows to recover cryptographic key Create a fake key from cryptographic key material 11
Software Attacks Cars are computer systems: Network of computers Critical systems (brakes, etc.) Entertainment Audio, Video Wireless Networks GSM/3G, Wireless interfaces (TPMS) Complexity brings new security problems IEEE S&P 2010, report 2011: from UC San Diego / Washington University Possible attacks to execute malicious code on the on board computers E.g. Prevent breaking/unexpected breaking Infection from internal bus (ODB II) or remote, wireless interfaces This could lead to theft, forced accidents 12
Agenda 1. Overview of Car Key Systems 2. Previous Attacks: in practice 3. Passive Keyless Entry and Start Systems 4. Relay Attacks 5. Analysis on 10 models 6. Conclusion 13
PKES Modes of Operation Normal mode of operation: Passive Open and Start Uses 2 radio channels Key Car Active Remote Open Mode: Button on the key One way messages Key Car Like previous remote active open keys Battery depleted mode Passive RFID bidirectional Key Car Key fob immobilizer chip Like immobilizers : centimeters Metallic key in the key fob 14
Passive Keyless Entry and Start PKES Need to be close (<2m) and the car opens Need to be in the car to start the engine No need for human action on the key 15
Passive Keyless Entry and Start 1. Periodic scan (LF) 2. Acknowledge proximity (UHF) 3. Car ID Challenge (LF) 4. Key Response (UHF) LF (120 135 KHz), UHF (315 433 MHz), (1-2 meters) (50-100 meters) 16
PKES Systems: Summary Cryptographic key authentication with challenge response Replaying old signals impossible Timeouts, freshness Car to Key: inductive low frequency signals Signal strength ~ d -3 Physical proximity Detected by reception of messages Induced in key s antenna The system is vulnerable to relay attacks 17
Agenda 1. Overview of Car Key Systems 2. Previous Attacks: in practice 3. Passive Keyless Entry and Start Systems (PKES) 4. Relay Attacks on PKES 5. Analysis on 10 models 6. Conclusion 18
Relay-over-cable Attack on PKES Very low cost attack (~50CHF) Independent of model / protocol / cryptography 19
Physical Layer Relay With Cable 20
Relay Over the Air Attack Tested up to 50 m Higher cost, (~1000 CHF) Fast and difficult to detect Independent of model / protocol / cryptography 21
Physical Layer Wireless Relay 2.5 GHz 22
Agenda 1. Overview of Car Key Systems 2. Previous Attacks: In Practice 3. Passive Keyless Entry and Start Systems 4. Relay Attacks 5. Analysis on 10 Models 6. Conclusion 23
Analysis on 10 Models Car models with PKES 10 models from 8 manufacturers All use LF/UHF technology None uses the exact same protocol Form recorded traces Some use longer messages Strong crypto? 24
Relay Over Cable vs. Model Cables 10, 30 and 60m Longer distances Depend on the setup 25
Key to Antenna Distance 26
How Much Delay is Accepted by the Car? The maximum distance of relay depends on Acceptable delay Speed of radio waves (~ speed of light ) Possibility to relay at higher levels? E.g. relay over IP? To know that we need to delay radio signals Various lengths of cable: Scope/signal generator: Software Defined Radios: not practical too slow still too slow 27
Inserting a Tunable Delay We used a Software Defined Radio: USRP/Gnuradio Minimum delay 15ms Samples processed by a computer Delays added by the USB bus We modified the USRP s FPGA to add tunable delays From 5µs to 10ms Buffering samples on the device Samples directly replayed Without processing on the computer 28
Maximum Accepted Delay vs. Model 35 µs => 5 Km 10 ms => 1500 Km Non physical layer relays difficult with most models 29
Implications of The Attack Relay on a parking lot One antenna near the elevator Attacker at the car while car owner waits for the elevator Keys in locked house, car parked in front of the house E.g. keys left on the kitchen table Put an antenna close to the window, Open and start the car without entering the house Tested in practice 30
Additionnal Insights When started the car can be driven away without maintaining the relay It would be dangerous to stop the car when the key is not available anymore Some beep, some limit speed No trace of entry/start Legal / Insurance issues 31
Agenda 1. Overview of Car Key Systems 2. Previous Attacks: In Practice 3. Passive Keyless Entry and Start Systems 4. Relay Attacks 5. Analysis on 10 Models 6. Conclusion 32
Countermeasures Immediate protection mechanisms Shield the key Remove the battery Seriously reduces the convenience of use Long term Build a secure system that securely verifies proximity e.g. : Realization of RF Distance bounding Usenix Security 2010 Still some challenges to address before a usable system 33
Conclusion This is a simple concept, yet extremely efficient attack Real world use of physical layer relay attacks Relays at physical layer are extremely fast, efficient All tested systems so far are vulnerable Completely independent of Protocols, authentication, encryption Techniques to perform secure distance measurement are required, on a budget Still an open problem 34
Questions? Contact : Aurélien Francillon aurelien.francillon@inf.ethz.ch Boris Danev bdanev@inf.ethz.ch Srdjan Capkun capkuns@inf.ethz.ch 35
Relevant Work A Practical Attack on KeeLoq, S. Indesteege, N. Keller, E. Biham, O. Dunkelman, and B. Preneel, EUROCRYPT 2008. On the Power of Power Analysis in the Real World: A Complete Break of the KeeLoq Code Hopping Scheme,T. Eisenbarth, T. Kasper, A. Moradi, C. Paar, M. Salmasizadeh, M. T. Manzuri Shalmani Crypto 2008 Breaking KeeLoq in a Flash -On Extracting Keys at Lightning Speed-, M. Kasper, T. Kasper, A. Moradi, C. Paar. Africacrypt 2009 Security analysis of a cryptographically-enabled RFID device S. C. Bono, M.Green, A. Stubblefield, A. Juels, USENIX Security 2005 36
Relevant Work Experimental Security Analysis of a Modern Automobile www.autosec.org Taking Control of Cars From Afar http://www.technologyreview.com/ computing/35094/ Security and Privacy Vulnerabilities of In-Car Wireless Networks: A Tire Pressure Monitoring System Case Study Wireless Car Sensors Vulnerable to Hackers http://www.technologyreview.com/communications/25962/ 37
Internals of a PKES Key 433 MHz Antenna 433MHz radio + MCU 130 khz passive RFID 130KHz antenna/coil 38
Passive Keyless Entry and Start Systems (1/2) System overview PKES car key Access regions 39
Tunable Delay: Data path minimum delay 15ms Data path : Radio => ADC => USRP => USB => PC => USB => USRP => DAC => Radio USRP s FPGA modification with tunable delays From 5µs to 10ms Buffering samples on the device before replay Data Path : Radio => ADC => FPGA (fifo adds delay) => DAC => Radio 40