Transcript Document
All slides © 2006 RSA Laboratories RFID (Radio-Frequency IDentication) takes many forms… “RFID” really denotes a spectrum of devices Basic “smart label” Toll payment plaque passive semi-passive passive no crypto no crypto some crypto few cm to few meters range several meters range several cm range Automobile ignition key Mobile phone “Smart labels”: EPC (Electronic Product Code) tags Barcode EPC tag Fast, automated scanning Line-of-sight Specifies object type Radio contact Uniquely specifies object Provides pointer to database entry for every object, i.e., unique, detailed history 2030: Week in the life of a milk carton • 30 April: RFID-tagged cow “Bessie” produces milk • 30 April: Milk transferred to RFID-tagged tank – • 1 May: RFID portal on truck records loading of refrigeration tanks – • Cow identity and milking time recorded in tank-tag database Truck also has active RFID (+GPS) to track geographical location and RFID transponder to pay tolls 2 May: Chemical-treatment record written to database record for milk barrel – Bessie’s herd recorded to have consumed mustard grass; compensatory sugars added to milk • 3 May: Milk packaged in RFID-tagged carton; milk pedigree recorded in database associated with carton tag • • • • 4 May: RFID portal at supermarket loading dock records arrival of carton 5 May: “Smart” shelf records arrival of carton in customer area 5 May 0930h: “Smart” shelf records removal of milk 5 May 0953h: Point-of-sale terminal records sale of milk (to Alice) 2030: Week in the life of a milk carton • 6 May 0953h: Supermarket transfers carton tag ownership to Alice’s smart home • • 6 May 1103h: Alice’s refrigerator records arrival of milk 6 May 1405h: Alice’s refrigerator records removal of milk; refrigerator looks up database-recorded pedigree and displays: “Woodstock, Vermont, Grade A, light pasturization, artisanal, USDA organic, breed: Jersey, genetic design #81726” • 6 May 1807h: Alice’s “smart” home warns domestic robot that milk has been left out of refrigerator for more than four hours 6 May 1809h: Alice’s refrigerator records replacement of milk • • 7 May 0530h: Domestic robot uses RFID tag to locate milk in refrigerator; refills baby bottle 2030: Week in the life of a milk carton • 6 May 0953h: Supermarket transfers carton tag ownership to Alice’s smart home • • 6 May 1103h: Alice’s refrigerator records arrival of milk 6 May 1405h: Alice’s refrigerator records removal of milk; refrigerator looks up database-recorded pedigree and displays: “Woodstock, Vermont, Grade A, light pasturization, artisanal, USDA organic, breed: Jersey, genetic design #81726” • 6 May 1807h: Alice’s “smart” home warns domestic robot that milk has been left out of refrigerator for more than four hours 6 May 1809h: Alice’s refrigerator records replacement of milk • • • • 7 May 0530h: Domestic robot uses RFID tag to locate milk in refrigerator; refills baby bottle 7 May 0531h: Robot discards carton; “Smart” refrigerator notes absence of milk; transfers order to Alice’s PDA/phone/portable server grocery list 7 May 2357h: Recycling center scans RFID tag on carton; directs carton to paper-brick recycling substation RFID Today: IN Your POcket Note: Often just emit static identifiers, i.e., they are just smart labels! Proximity cards in your pocket RFID helps secure hundreds of millions of automobiles •Cryptographic challenge-response •Philips claims more than 90% reduction in car theft thanks to RFID! •Note: some devices, e.g., Texas Instruments DST, are weak… f Automobile ignition keys in your pocket •ExxonMobil SpeedpassTM •RFID now offered in all major credit cards in U.S.… Payment devices in ANIMALs • Cattle • Housepets 50 million+ “Not Really Mad” The cat came back, the very next day… on People • • • • Schools Amusement parks Hospitals In the same vein: mobile phones with GPS… In PAssports • Dozens of countries issuing or soon to issue RFID-enabled passports • Other identity documents, e.g., drivers’ licenses, to follow In Mobile phones NFC (Near-Field Consortium) Showtimes: 16.00, 19.00 • Also, ticket purchases, payments, comparison shopping Phone can act as reader or tag • NFC is a general-purpose protocol • Already available in some models In Currency? • Talk in 2003-4 of planting RFID tags in 10,000 Yen banknotes and Euro banknotes • Talk has dissipated • Main interest: anti-counterfeiting In pharmaceuticals • Anti-counterfeiting: Better supply-chain visibility means less fraud – U.S. govt. urging RFID to combat counterfeiting of drugs • Medical compliance: Greater independence (and privacy!), particularly for elderly The consumer privacy problem Here’s Mr. Jones in 2020… Wig Replacement hip model #4456 medical part #459382 (cheap polyester) Das Kapital and Communistparty handbook 1500 Euros in wallet 30 items of lingerie Serial numbers: 597387,389473 … …and the tracking problem Wig serial #A817TS8 • Mr. Jones pays with a credit card; his RFID tags now linked to his identity; determines level of customer service – Think of car dealerships using drivers’ licenses to run credit checks… • Mr. Jones attends a political rally; law enforcement scans his RFID tags • Mr. Jones wins Turing Award; physically tracked by paparazzi via RFID Suica Image courtesy of Kevin Fu Suica Images courtesy of Kevin Fu What data are vulnerable? CURRENT BALANCE Travel history: visited stations and dates Details of merchandise purchase Image courtesy of Kevin Fu RFID privacy Only definitive way to achieve privacy is: – Emit an identifier only – Change identifier across reads Wig serial #A817TS8u RFID privacy Only definitive way to achieve privacy is: – Emit only an identifier – Change identifier across reads #A817TS8u RFID privacy Only definitive way to achieve privacy is: – Emit only an identifier – Change identifier across reads #Z87d68aK The authentication problem Good readers, bad tags Mr. Jones in 2020 Counterfeit! Replacement hip medical part #459382 Mr. Jones’s car is stolen! 1500 Euros in wallet Mad-cow hamburger lunch Counterfeit! Serial numbers: 597387,389473 … Won’t crypto solve our problems? Side-channel countermeasures AES We can do: • Challenge-response for authentication • Mutual authentication and/or encryption for privacy But: 1. Moore’s Law vs. pricing pressure 2. Beyond simple “terrestrial” problems, basic cryptography may not be enough… This is the theme of our talk! Simple authentication: Possession is the law • How does Alice’s refrigerator get read/write privileges for the history for the milk carton bearing tag T? • The straightforward approach: – A central registry R shares symmetric key k with the tag T – Alice’s refrigerator acts as authentication proxy between R and T – Tag T authenticates via challenge-response c k Registry R r = fk(c) c r = fk(c) k Simple authentication: Possession is the law • But what if the tag is on Alice’s wristwatch? – Should any nearby reader be able to read tag history? – Should any nearby reader be able to modify tag history? • What if registry R is unavailable? – Will the tag carry information on board? – If so, who can access it? – Does Alice’s baby get its milk? The VeriChipTM + = ??? Human-implantable RFID The VeriChipTM • Proposed for medical-patient identification • Also proposed and used as an authenticator for physical access control, a “prosthetic biometric” – E.g., Mexican attorney general purportedly used for access to secure facility + = • What kind of cryptography does it have? – None: It can be easily cloned • So shouldn’t we add a challenge-response protocol? Human-implantable RFID • Cloning may actually be a good thing The VeriChipTM • Physical coercion and attack – In 2005, a man in Malaysia had his fingertip cut off by thieves stealing his biometric-enabled Mercedes – What would happen if the VeriChip were used to access ATM machines and secure facilities? • Perhaps it is better then if tags can be cloned and are not used for authentication—only for identification • But if a tag is cloneable, and used for identification, does that mean that privacy is impossible? – I.e., does cloneability imply an ability to track? Private identification • A very simple scheme allows for simultaneous cloneability and privacy • El Gamal public-key cryptosystem: – Randomized scheme: C = EPK,r [m] – Semantic security: Cannot distinguish between ciphertexts C and C’ on known plaintexts without knowledge of SK • Adversary cannot distinguish between C = EPK,r [Alice] and C’ = EPK,r’ [Bob] Private identification Our simple scheme: Officer Alice SK “Proceed to authenticate Officer Alice” Private identification Take two: Officer Alice SK “Proceed to authenticate Officer Alice” Private identification • Semantic security → An attacker who intercepts C and C’ cannot tell if they come from the same chip – Attacker cannot identify or track Alice • But attacker can still clone Alice’s chip! • El Gamal re-encryption (homomorphism): – Let U = EPK,r [1] have uniformly random r – Then given C = EPK,r’ [m], the distribution CxU is uniform over ciphertexts on m • Clone chip selects U and outputs CxU • Clone chip is indistinguishable from Alice’s! Attacker’s perspective Alice’s chip Attacker’s perspective Attacker can simulate Alice’s chip, but… •He cannot track Alice •He may not even know whose chip he’s cloned! “Proceed to authenticate Officer Alice” The covert-channel problem Suppose there is a secret sensor… Officer Alice SK “Officer Alice has low blood pressure and high blood-alcohol” The covert-channel problem Suppose there is a secret sensor… Officer Alice SK “Officer Alice recently passed near the RFID reader of a casino” The covert-channel problem Suppose there is a secret sensor… Officer Alice SK “Mercury switch indicates that Officer Alice took a nap this afternoon.” How can we ensure no covert channels? • Must make outputs deterministic • Can also, e.g., give PRNG keys to Alice • But can we: – Allow Alice to verify covert-freeness without exposing secret keys to her? – Enable a third party to verify covert-freeness? • It turns out that privacy and such verifiable covert-freeness are contradictory! Covert-freeness detector A A’ “No covert channel” “Yes, covert channel suspected” Here’s a covert channel! 1. Create identifier for Bob • Bob need not actually own a chip 2. Alice’s chip does following: • • If no nap, output ciphertexts A, A’, A’’, etc. with Alice’s identity If Alice has taken a nap, output ciphertexts B,B’,B’’, etc. with Bob’s identity Suppose we detect the covert channel… A “No covert channel” A’ Suppose we detect the covert channel… A “Yes, covert channel B suspected” Then we can distinguish between Alice and Bob: Privacy is broken! A “Yes, covert channel B suspected” Then we can distinguish between Alice and Bob: Privacy is broken! A “A and B B represent different people” Covert-freeness and privacy? • Let’s change (relax) the definition of privacy! • If non-sequential tag outputs are checked, detector learns nothing… READ EVENTS “?????” Covert-freeness and privacy? • Detector can do pairwise check only… • Achievable “efficiently” with pairings-based cryptography (ECC) READ EVENTS “Covert-free pair” Covert-freeness and privacy? • Privacy is largely preserved because of locality • Covert-freeness checkable probabilistically, i.e., with spot checks READ EVENTS “Covert-free pair” Returning to basic issue of privacy: Kill codes • EPC tags have a “kill” function • • • Developed for EPC to protect consumers after point of sale • • • On receiving password, tag self-destructs Tag is permanently inoperative “Dead tags tell no tales” Privacy is preserved Simple and categorical, but not a wholly satisfying solution… Problem 1: Post-consumer uses of tags k Dead tags perhaps not harmful, but certainly not beneficial… Problem 2: RF signatures • Y. Oren and A. Shamir attacked EPC kill passwords via over-theair power analysis Found that dead tags are detectable! • – • Backscatter from antennas Hypothesize manufacturer type may be learnable •3 type A tags (merchandise) •2 type B tags (medication) •10 type C tags (500-Euro banknotes) • • Probably of limited significance, but still bears on privacy Do tags possess uniquely detectable RF fingerprints? – • Device signatures a staple of electronic warfare Cryptography would not help here! So what might solve our problems? • The fact that privacy is not RFID specific • Laws and policy • RFID security as a database problem – Reduces problem to access control, but: – Accept tracking of identifiers – Create further dependence on network connectivity So what might solve our problems? • Higher-powered intermediaries like mobile phones – RFID “Guardian” and RFID REP Please show reader certificate and privileges So what might solve our problems? • Cryptography! – Urgent need for cheaper hardware for primitives and better sidechannel defenses • Some of talk really in outer limits, but basic caveats are important: – Pressure to build a smaller, cheaper tags without cryptography – RFID tags are close and personal, giving privacy a special dimension – RFID tags change ownership frequently – Key management will be a major problem • Think for a moment after this talk about distribution of kill passwords… • Are there good hardware approaches to key distribution, e.g., proximity as measure of trust To learn more • Largely collaborative work within RFID CUSP – www.rfid-cusp.org – Papers available on publications page • Papers: – “RFID security and privacy: a research survey” – “The security implications of VeriChipTM cloning,” • Joint work with J. Halamka, A. Stubblefield, and J. Westhues – “Covert channels in privacy-preserving identification systems” • Forthcoming joint work with Dan Bailey – “Power analysis of RFID tags” (on Internet; not RFID-CUSP) • Y. Oren and A. Shamir