Slide 1Modern Implants Have WirelessBenefits of WirelessBenefits of WirelessSecurity AttacksHow Do We Protect Against Such Attacks?Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Shield simultaneously:Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Empirical ResultsSlide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Securing Wireless Medical ImplantsShyamnath GollakotaHaitham HassaniehBenjamin RansfordDina Katabi Kevin FuModern Implants Have Wireless Cardiac Defibrillators NeurostimulatorsCochlear Implants•Easier communication with implant•Remote monitoringBenefits of Wireless•Easier communication with implant•Remote monitoringReduces hospital visits by 40% and cost per visit by $1800[Journal of the American College of Cardiology, 2011]What about security?What about security?Benefits of Wireless1) Passive attack: Eavesdrop on private dataPatient diagnosis, vital signs 2) Active attack: Send unauthorized commandsTurn off therapies, Security Attacks[Halperin’08] demonstrated attacks using software radios[Halperin’08] demonstrated attacks using software radiosdeliver electric shockHow Do We Protect Against Such Attacks? Cryptography?Problems with Adding Cryptography on Implants•In emergencies, patient may be taken to a foreign hospital where doctors don’t have the secret key•Millions of patients already have implants with no crypto; would require surgery to replaceIdeally, secure implants without modifying themIdeally, secure implants without modifying themDelegate security to an external device •In emergencies, doctor turns external device off•Helps people who already have implants•In emergencies, doctor turns external device off•Helps people who already have implantsWireless DeviceSolution IdeaShield Protects from Active Attacks•Shield jams unauthorized commandsTurn off therapy Implants can’t decode or react to commandShield Protects from Active AttacksImplant ID•Shield listens on mediumImplant protected from active attacksImplant protected from active attacksBut How to Protect from Passive Attacks?Simply jamming prevents everyone from getting data!How can we prevent eavesdropper from getting data while delivering data to doctor?How can we prevent eavesdropper from getting data while delivering data to doctor?Analog one-time padNaïve Sol: Shield jams implant tx so attacker can’t decodeOnly a node that has the key can decryptKeyMessageEncryption Classic Approach: One-Time PadEncrypted Message=MessageEncrypted MessageKey=DecryptionChannel sums implant’s signal with shield’s random signalImplant’s signalshieldjamsRandom SumEavesdropper doesn’t know jamming signal  can’t decodeShield knows the jamming signal  subtracts it  decodes implant’s transmission Protect from Passive Attacks: Analog One-Time PadJamming signal acts like the key in one-time padJamming signal acts like the key in one-time padTraditional SystemPutting it togetherOur SystemPutting it togetherDoctor configures the shield with a secret key  Shield acts as proxyUse encryptionShield encrypts the implant data and forwards it to doctor•First system that secures wireless implants without modifying them•Design that simultaneously jams and decodes medical implant transmissions•Implemented and evaluated using commercial cardiac defibrillatorsEffective at protecting the implants ContributionsNeed radio that transmits and receives simultaneously, i.e., a full-duplex radioNeed radio that transmits and receives simultaneously, i.e., a full-duplex radio•Jams the implant’s signal•Decodes the implant’s signalShield simultaneously:Medical implant work at 400 MHztx1rxtx2dHow to Design Full-Duplex for Medical Implants?Cancel outMobicom’2010 wavelength2d + wavelength2d + ≈ 40 cm wavelength2Too large for portable devicesToo large for portable devicesrxtx2Jamming signalAntidotetx1tx2rxFull-Duplex Without Antenna SeparationShieldAntidote signal cancels out jamming signal •Shield can simultaneously jam and receive•Design is small and portable•Shield can simultaneously jam and receive•Design is small and portableantidoteselfShhcrossSjamming0SantidotehselfhcrossSjammingReduce signal power by 100 million times•Requires highly linear components •ExpensiveCan we build shield with significantly less cancellation?30–40 dB is sufficient!But, Full-Duplex Needs 60–80 dB Cancellation0 5 10 15 20 25 3000.10.20.30.40.5 Decode Implant’s signal•FSK signal•Implant signal has a 10 dB SNR•50% bit error rateJamming power / Implant power (in dB)Bit Error RateShield RequirementsJam eavesdropper0 5 10 15 20 25 3000.10.20.30.40.5 Decode Implant’s signal•FSK signal•Implant signal has a 10 dB SNR•50% bit error rate•Jamming power 20 dB higher than implant’s powerJamming power / Implant power (in dB)Bit Error RateShield RequirementsJam eavesdropperTime20 dB10 dBShield Requirements Decode Implant’s signal•FSK signal•Implant signal has a 10 dB SNR•50% bit error rate•Jamming power 20 dB higher than implant’s powerCancel 30 dBJam eavesdropperShield requires only 30 dB cancellationShield requires only 30 dB cancellationEmpirical Results• Medtronic cardiac implants• Medtronic programmer• Implement attacker and shield on USRP2s• Simulate human implantation: bacon & beef Evaluation•20-location test bed•Fix locations of implant and shield•Node at every other location acts as adversaryTestbed30 m20cmPassive AttacksEavesdrop on private data•Decode implant’s transmissions•Use optimal FSK decoder0.2 0.4 0.6 0.8 100.20.40.60.81Attacker Bit Error RateCDF over attacker locations Can Eavesdropper do Better Than Random Guess?0.2 0.4 0.6 0.8 100.20.40.60.81Random GuessCan Eavesdropper do Better Than Random Guess?CDF over attacker locations Attacker Bit Error Rate0.2 0.4 0.6 0.8 100.20.40.60.81Random GuessWith JammingCan Eavesdropper do Better Than Random Guess?CDF over attacker locations Attacker Bit Error RateIndependent of location, eavesdropper can do no better than a random guessIndependent of location, eavesdropper can do no better than a random guessPacket Loss at ShieldCDFCan Shield Decode Implant’s Messages?0 0.01 0.01 0.02 0.02 0.0300.20.40.60.81Packet Loss at ShieldCDFCan Shield Decode Implant’s Messages?0 0.01