Transcript RFID: Security and Privacy for Five-Cent Computers

RFID: Security and Privacy for
Five-Cent Computers
Ari Juels
Principal Research Scientist
RSA Laboratories
USENIX Security 2004
LABORATORIES
What is a Radio-Frequency
Identification (RFID) tag?
• In terms of appearance…
Chip (IC)
Antenna
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:
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:
Basic
RFID
Tag
EZ Pass
SpeedPass
Mobile phone
What is a 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”
“Plastic #3”
“5F8KJ3”
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
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
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
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
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
Approach 2: “Kill” RFID tags
Problem:
RFID tags are
much too useful
in “live” state…
We already
have SpeedPass,
etc., and then…
Tomorrow’s consumer applications
• Prada, Soho NYC
– Personalization / accessorization
• 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
Consumers will not want their tags “killed,” but should still have a
right to privacy!
Approach 3: Policy and legislation
• Undoutedly helpful if thought through well, but…
• “Good Housekeeping” seal
• Retailer’s guarantee means little since tags may be
read by anyone!
• FTC Section 5 (“Deceptive practices”) and the
like are similarly limited
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
Cryptographers’ view of device security –
emphasis on “oracle” access
Welcome to Hell
IT Department
011001010010
A basic RFID tag cannot survive…
Welcome to Hell
IT Department
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., capacitordischarge 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
0
1
?
00
000
001
01
010
10
011
100
11
101
110
111
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
#458790
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!
• Polite blocking: Blocker informs reader of its
presence
Your humble servant
requests that you not
scan the privacy zone
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
[Juels and Brainard WPES ‘03]
• 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
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
The Privacy Debate
VeriChip™
Paying for drinks with wave of the hand
Club-goers in Spain get implanted chips for
ID, payment purposes
WorldNetDaily, 14 April 2004
www.rapturechrist.com/666.htm
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.spychips.com, www.stoprfid.com
“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.
for more information:
(unofficial URL)