RFID: Security and Privacy for Five-Cent Computers

Ari JuelsPrincipal Research Scientist

RSA LaboratoriesUSENIX Security 2004

LABORATORIES

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?

SpeedPassMobile phone

EZ PassBasicRFIDTag

• 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 pointerto database entryfor 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 Eurosin wallet

Serial numbers:597387,389473

…

Wigmodel #4456

(cheap polyester)

30 items of lingerie

Das Kapital and Communist-

party handbook

Replacement hipmedical part #459382

The consumer privacy problem

Here’sMr. Jonesin 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 solutionsto the privacy problem

Approach 1: Cover RFID tags with protective mesh or foil

Problems: (1) Makes locomotiondifficult(2) Shops don’t like distributing tools for theft

Problem: RFID tags aremuch too usefulin “live” state…

Approach 2: “Kill” RFID tags

We alreadyhave 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’sgot 700 Euro and a Rolex…”

Whom will the FTC prosecute now?

Three take-home messages ofthis 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

011001010010

Welcome to Hell IT Department

A basic RFID tag cannot survive…

011001010010

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” TagBlocker 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

000 001 010 011 100 101 110 111

00 01 10 11

0 1

?

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 bottlesof Merlot#458790

Blocker tag system should protect privacy but stillavoid 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 RXA Pharmacy

RFID-tagged bottle + “Blocker” bag

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 RFIDNokia 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 proximity2. Mobile phone deactivates tags or imbues with

changing pseudonyms3. Mobile phone simulates tags to readers, enforcing

user privacy policy4. Mobile phone “releases” tags when tags about to exit

range

VeriChip™

The Privacy Debate

Paying for drinks with wave of the handClub-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™.

www.rapturechrist.com/666.htm

“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.”

www.spychips.com, www.stoprfid.com

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.

for more information:

(unofficial URL)