On the Security of Millimeter Wave Vehicular Communication Systems using Random Antenna Subsets Mohammed Eltayeb*, Junil Choi*, Tareq Al-Naffouri #, and Robert W. Heath Jr.* * Wireless Networking and Communications Group, Department of Electrical and Computer Engineering, The University of Texas at Austin # Electrical Engineering Department, King Abdullah University of Science and Technology (KAUST) Authors * are funded by U.S. Department of Transportation through D-STOP Tier 1 University Transportation Center and Texas Department of Transportation CAR-STOP
Security threats in V2X Message replay attack Eavesdropping attack Information extraction T=T+τ: slow down T=0: slow down T=T+τ: all clear Message falsification attack Important to secure communication links M. Raya, P. Papadimitratos, and J. Hubaux, Securing vehicular communications, IEEE Wireless Commun., vol. 13, no. 5, pp.8-15, Oct. 2006. J. Hubaux, S. Capkun, and J. Luo, The security and privacy of smart vehicles, IEEE Security and Privacy Mag., vol. 2, no. 3, May 2004, pp. 49-55. 2
Challenges with existing encryption techniques Require exchange of keys (resource intensive) Key distribution & management becomes challenging as the network scales Broadcast of public key not possible in mmwave due to high path loss Fail if keys are compromised Challenges motivate keyless physical layer (PHY) encryption M. Raya, P. Papadimitratos, and J. Hubaux, Securing vehicular communications, IEEE Wireless Commun., vol. 13, no. 5, pp.8-15, Oct. 2006. J. Hubaux, S. Capkun, and J. Luo, The security and privacy of smart vehicles, IEEE Security and Privacy Mag., vol. 2, no. 3, May 2004, pp. 49-55. 3
Physical layer (PHY) encryption: limitations Robert W. Heath Jr. (2016) Tx uses multiple antennas to degrade eavesdropper s channel Does not rely on upperlayer data encryption or secret keys PHY LAYER SECURITY LIMITATIONS Traditional PHY encryption not suitable for mmwave systems (hardware limitations) MmWave PHY techniques based on switched arrays do not fully exploit the array gain 4
Proposed mmwave PHY encryption approach Design analog precoder to distort sidelobes Exploit all transmitter antennas Analog design respects mmwave hardware constraints Sidelobe distortion jams eavesdroppers No need for antenna switches 5
System model Tx AoD gain due to reflected path Phase shifter Two-ray model has been reported to provide good fit in open road Tx Antenna H. L. Van Trees, Optimum array processing (detection, estimation, and modulation theory, part IV), 1st ed. WileyInterscience, Mar. 2002. M. Boban, et al., Geometry-based vehicle-to-vehicle channel modeling for large-scale simulation, IEEE Trans. Veh. Technol., vol. 63, no. 9, pp. 4146-4164, Nov. 14. 6
System model (cont d) Received signal model Tx precoder received signal symbol index transmit power path loss Rx antenna gain noise Tx symbol Tx-Rx channel Two-ray LOS narrow band channel with perfect synchronization Transmitter is equipped with target receiver s AoD only All receivers have perfect channel knowledge H. L. Van Trees, Optimum array processing (detection, estimation, and modulation theory, part IV), 1st ed. WileyInterscience, Mar. 2002. M. Boban, et al., Geometry-based vehicle-to-vehicle channel modeling for large-scale simulation, IEEE Trans. Veh. Technol., vol. 63, no. 9, pp. 4146-4164, Nov. 14. 7
Proposed PHY encryption Resulting pattern Transmit antenna Robert W. Heath Jr. (2016) M antennas co-phased to coherently combine at Rx distorted pattern distorted pattern Remaining antennas cophased to destructively combine at Rx Coherent combining Destructive combining (Randomized with every symbol transmission) Destructive combining at Tx distorts sidelobes and jams eavesdroppers 8
Precoder design The n th entry of the precoder f(k) is transmit symbol index Rx AoD coherent combining subset even entries of destructive combining subset odd entries of destructive combining subset Percoder design is based on Analog Beamforming with a single RF chain 9
Received signal At target Rx ( θ = θ R ) transmit subset size Robert W. Heath Jr. (2016) Rx array gain no. of Tx antennas constant At eavesdropper ( θ θ R ) eavesdropper array gain random variable Beam pattern converges to a random variable at non-rx directions 10
Simulation results Setup Frequency 60 GHz, BW = 50MHz, power 37dBm Standard two-ray channel model Tx equipped with32 antennas and one RF chain Rx and eavesdropper equipped with 16 and 32 antennas Tx subset size is M = 0.75xNT Matched-filter Rx beamforming is assumed Rx distance is 30 m, eavesdropper distance is 10 m Rx is located along an AoD = 100 deg. Secrecy throughput SNR at target receiver SNR at eavesdropper High secrecy throughput except at AoD = 100 o N. Valliappan, et al., Antenna subset modulation for secure millimeter-wave wireless communication, IEEE Trans. Commun., vol. 61, no. 8, pp.3231-3245, Aug. 2013. 11
Varying the transmission subset size Using all antennas increases the beam pattern variance at non-rx directions when compared to switched array techniques There is an optimal subset size that maximizes the secrecy throughput N. Valliappan, et al., Antenna subset modulation for secure millimeter-wave wireless communication, IEEE Trans. Commun., vol. 61, no. 8, pp.3231-3245, Aug. 2013. 12
Conclusions Message replay attack Eavesdropping attack Information extraction Robert W. Heath Jr. (2016) T=0: slow down Message falsification attack Large dimensional antenna arrays can be exploited to jam eavesdroppers Proposed technique is keyless and transparent to existing receivers Proposed technique can be used to augment higher layer security techniques 13
Questions? 14