RFID: Security and Privacy for Five-Cent Computers Ari Juels Principal Research Scientist RSA Laboratories USENIX Security ¢5¢

What is a Radio-Frequency Identification (RFID) tag? Chip (IC) Antenna In terms of appearance…

What is an RFID tag? You may own a few RFID tags… –Proximity cards (contactless physical-access cards) –ExxonMobil Speedpass –EZ Pass RFID in fact denotes a spectrum of devices:

You may own a few RFID tags… –Proximity cards (contactless physical-access cards) –ExxonMobil Speedpass –EZ Pass RFID in fact denotes a spectrum of devices: What is an RFID tag? SpeedPass Mobile phone EZ Pass Basic RFID Tag

Characteristics: –Passive device – receives power from reader –Range of up to several meters –In effect a “smart label”: simply calls out its (unique) name and/or static data “74AB8” “5F8KJ3” “ Plastic #3” What is a basic RFID tag?

The capabilities of a basic RFID tag Little memory –Static 64-to-128-bit identifier in current ultra-cheap generation (five cents / unit) –Hundreds of bits soon –Maybe writeable under good conditions Little computational power –A few thousand gates –Static keys for read/write permission –No real cryptographic functions available

The grand vision: RFID as next-generation barcode Barcode RFID tag Line-of-sight Radio contact Specifies object type Uniquely specifies object Fast, automated scanning Provides pointer to database entry for every object, i.e., unique, detailed history

Some applications Better supply-chain visibility -- #1 compelling application U.S. DHS: Passports U.S. FDA: Pharmaceuticals, anti-counterfeiting Libraries Housepets – approx. 50 million Parenting logistics –Water-park with tracking bracelet RFID in Euro banknotes (?)

There is an impending explosion in RFID-tag use EPCglobal –Joint venture of UCC and EAN –Wal-Mart, Gillette, Procter & Gamble, etc. –Spearheading EPC (electronic product code) data standard for tags –Putting finishing touches on basic-tag standard (Class 1 Gen 2) this week Wal-Mart requiring top 100 suppliers to start deploying RFID in 2005 Other retailers and DoD following Wal-Mart lead Pallet and case tagging first -- item-level retail tagging seems years away Estimated costs 2005: $0.05 per tag; hundreds of dollars per reader 2008: $0.01 per tag; several dollars per reader (?) A broader vision: “Extended Internet”

The Problems of Privacy and Security

RFID means a world with billions of ant-sized, five-cent computers Highly mobile Contain personal information Subject to surreptitious scanning Again, no cryptography… Access control difficult to achieve Data privacy difficult to achieve

1500 Euros in wallet Serial numbers: , … Wig model #4456 (cheap polyester) 30 items of lingerie Das Kapital and Communist- party handbook Replacement hip medical part # The consumer privacy problem Here’s Mr. Jones in 2020…

Wig serial #A817TS8 …and the tracking problem 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

Early examples of consumer backlash 42% of Google results on “RFID” include word “privacy” CASPIAN (Consumers Against Supermarket Privacy Invasion and Numbering) –Diatribes on RFID at: Spychips.com BoycottGillette.com BoycottBenetton.com –National news coverage: NY Times, Time, etc. Wal-Mart “smart-shelf project” cancelled Benetton RFID plans (purportedly) withdrawn

Some problems you don’t hear about Corporate espionage: Privacy is not just a consumer issue –Eavesdropping on warehouse transmissions –Scanning of shelves for turnover rates Tag counterfeiting –Automation means dependence! –Think about RFID-enabled medicine cabinets… Special demands of U.S. Department of Defense –“DoD would be like Wal-Mart… if Christmas were a random event every five years, and a stockout meant that everyone in the store could die…” -Nicholas Tsougas, DoD

Some proposed solutions to the privacy problem

Approach 1: Cover RFID tags with protective mesh or foil Problems: (1) Makes locomotion difficult (2) Shops don’t like distributing tools for theft

Problem: RFID tags are much too useful in “live” state… Approach 2: “Kill” RFID tags We already have SpeedPass, etc., and then…

Tomorrow’s consumer applications Tagged products –Clothing, appliances, CDs, etc. tagged for store returns and locatable in house “Smart” appliances –Refrigerators that automatically create shopping lists and when milk expires –Closets that tell you what clothes you have available, and search the Web for advice on current styles, etc. –Washing machines that detect improper wash cycle “Smart” print –Airline tickets that indicate your location in the airport –Business cards Aids for cognitively impaired, e.g., “smart” medicine cabinets –Project at Intel Recovery of stolen goods (?) Recycling –Plastics that sort themselves Prada, Soho NYC –Personalization / accessorization Consumers will not want their tags “killed,” but should still have a right to privacy!

Undoutedly helpful if thought through well, but… Approach 3: Policy and legislation Retailer’s guarantee means little since tags may be read by anyone! FTC Section 5 (“Deceptive practices”) and the like are similarly limited “Good Housekeeping” seal

Another possible use of RFID More efficient mugging “Just in case you want to know, she’s got 700 Euro and a Rolex…” Whom will the FTC prosecute now?

Three take-home messages of this talk 1.Deployed naïvely, embedding of RFID tags in consumer items can present a serious danger to privacy and security of consumers and enterprises alike in the future. 2.RFID is a technology with high promise. It would be unfortunate if security problems scotched it. 3.As technologists we must help to achieve a good balance of PRIVACY/SECURITY and UTILITY.

Technical Approaches to Enhancing RFID Privacy

Welcome to Hell IT Department Cryptographers’ view of device security – emphasis on “oracle” access

Welcome to Hell IT Department A basic RFID tag cannot survive…

For RFID, we can consider different and weakened adversarial assumptions Adversary is not present 24 hours a day –Adversary must be physically close to tag to scan it We can deploy security protocols on physical channels – not just logical ones External, higher-capability devices can help protect tags

First approach [Juels, SCN ’04]: Minimalist cryptography Key observation: Adversary must have physical proximity to tag to interact with it Key assumption: Adversary can query tag only limited number of times in given attack session Example: Passive eavesdropping –Adversary only hears queries made by legitimate readers Example: Building access –Adversary has limited time to query tags in parking lot before employees authenticate to door readers Example: Readers scattered around city –Pedestrians within range of reader for limited time

Pseudonym rotation Set of pseudonyms known only by trusted verifier Pseudonyms stored on tag Limited storage means at most, e.g., 10 pseudonyms Tag cycles through pseudonyms “74AB8” “MMW91” = ?

Strengthening the approach Strengthen restriction on adversarial queries using “throttling” –Tag enforces pattern of query delays via, e.g., capacitor- discharge timing Pseudonym refresh –Trusted reader provides new pseudonyms –Pseudonyms must be protected against eavesdropping and tampering using encryption, but tags cannot do standard cryptography! –Can load up tag with one-time pads – assuming adversary is not always present, some pads will be secret! Not for retail items, which must include basic item information. Perhaps for prox. cards, tickets, etc.?

Second Approach [Juels, Rivest, & Szydlo CCS ‘03]: The “Blocker” Tag

“Blocker” Tag Blocker simulates all (billions of) possible tag serial numbers!! 1,2,3, …, 2023 pairs of sneakers and… (reading fails)…

“Tree-walking” anti-collision protocol for RFID tags ?

In a nutshell “Tree-walking” protocol for identifying tags recursively asks question: –“What is your next bit?” Blocker tag always says both ‘0’ and ‘1’! –Makes it seem like all possible tags are present –Reader cannot figure out which tags are actually present –Number of possible tags is huge (at least a billion billion), so reader stalls

Two bottles of Merlot # Blocker tag system should protect privacy but still avoid blocking unpurchased items

Consumer privacy + commercial security Blocker tag can be selective: –Privacy zones: Only block certain ranges of RFID-tag serial numbers –Zone mobility: Allow shops to move items into privacy zone upon purchase Example: –Tags might carry a “privacy bit” –Blocker blocks all identifiers with privacy bit on –Items in supermarket have privacy bit off –On checkout, leading bit is flipped from off to on PIN required, as for “kill” operation

Polite blocking We want reader to scan privacy zone when blocker is not present –Aim of blocker is to keep functionality active – when desired by owner But if reader attempts to scan when blocker is present, it will stall! Your humble servant requests that you not scan the privacy zone Polite blocking: Blocker informs reader of its presence

More about blocker tags Blocker tag can be cheap –Essentially just a “yes” tag and “no” tag with a little extra logic –Can be embedded in shopping bags, etc. With multiple privacy zones, sophisticated, e.g., graduated policies are possible Works for ALOHA anti-collision too

An Example: The R X A Pharmacy

RFID-tagged bottle + “Blocker” bag

“Soft” Blocking Idea: Implement polite blocking only – no hardware blocking –A little like P3P… External audit possible: Can detect if readers scanning privacy zone Advantages: –“Soft blocker” tag is an ordinary RFID tag –Flexible policy: “Opt-in” now possible e.g., “Medical deblocker” now possible Weaker privacy, but can combine with “hard” blocker [Juels and Brainard WPES ‘03]

Third approach: Personal Simulator or Proxy for RFID Nokia mobile-phone RFID kit available in 2004 –Readers will be compact, available in personal devices We might imagine a simulation lifecycle: 1.Mobile phone “acquires” tag when in proximity 2.Mobile phone deactivates tags or imbues with changing pseudonyms 3.Mobile phone simulates tags to readers, enforcing user privacy policy 4.Mobile phone “releases” tags when tags about to exit range

VeriChip™ The Privacy Debate Paying for drinks with wave of the hand Club-goers in Spain get implanted chips for ID, payment purposes WorldNetDaily, 14 April 2004

NEW Subdermal Biochip Implant for Cashless Transactions - is it the Mark? The mark is a microchip assembly which will be implanted under the skin of the right hand. Later on, the mark will be implanted under the forehead, so people who have no right hand could also have the mark. The microchip assembly, called radio frequency identification (RFID) is already used in animals. In dogs, the RFID is placed between the shoulder blades, and in birds it is implanted under the wing. Now there is a one for humans called VeriChip™.

“Unlike a bar code, [an RFID tag] can be read from a distance, right through your clothes, wallet, backpack or purse -- without your knowledge or consent -- by anybody with the right reader device. In a way, it gives strangers x-ray vision powers to spy on you, to identify both you and the things you're wearing and carrying.”

RFID realities Deployers can scarcely get RFID working at all! UHF tags hard to read near liquids, like water –You are salt water so… –If you’re worried about your sweater being scanned, wear it! And even when range is good… –In NCR automated point-of-sale trials, participants paid for groceries of people behind them… Consumer goods manufacturers and retailers don’t want to drive customers away Corporations and governments don’t make very effective use of data anyway

“Given the potentially huge benefits to consumers from wide-scale deployment of RFID, including higher productivity and lower prices, the privacy community knows that the only way they can stop RFID at the consumer level is to make all sorts of outlandish claims about the Orwellian uses of RFID, which either can’t happen or are so unlikely as to be a non-issue.” Robert Atkinson, Progressive Policy Institute

Admonitions to privacy naysayers The technology will improve in ways we may not expect –Industry has an incentive to overcome obstacles –Tag power, reader sensitivity, antenna Standards and legacy systems stick around for years – we should try to build flexibility and safeguards in early An RFID tag is not like a cookie – psychologically more potent –If people think there’s a privacy problem, then there’s a problem Security and privacy are enabling Let us not forget the salutary warning of the 9/11 Commission: “Failure of imagination”

Open avenues of research PIN distribution –Cross-enterprise data flows Broken crypto –“Shrinking generators” analyzed in weaker adversarial model Adversarial models Anti-cloning –Sports memorabilia, FDA, etc.

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