RFID SECURITY

Network Security - IT653

Deepti Agrawal

KReSIT, IIT Bombay

What is RFID?

Radio-Frequency Identification Tag

Chip

Antenna

Holds a small amount of unique data – a serial number or other unique attribute of the item

The data can be read from a distance – no contact or even line of sight necessary

How Does RFID Work?

Tags (transponders)Attached to objects, call out their (unique) name and/or static data on a special radio frequency

02.3DFEX4.78AF51

EasyToll card #816

Reader (transceiver)Reads data off the tagswithout direct contact

Radio signal (contactless)

Range: from 3-5 inches to 3 yards

DatabaseMatches tag IDs tophysical objects

RFID Tag Power Sources

Passive (this is what mostly used now)• Tags are inactive until the reader’s interrogation signal “wakes”

them up• Cheap, but short range only

Semi-passive• On-board battery, but cannot initiate communication

• Can serve as sensors, collect information from environment: for example, “smart dust” for military applications

• More expensive, longer range

Active• On-board battery, can initiate communication

The capabilities of a basic RFID tag

Little memory

• Static 64-to-128-bit identifier in current ultra-cheap generation

Little computational power

• A few thousand gates

• Static keys for read/write permission

Not enough resources to support public- or symmetric-key cryptography

• Cannot support modular arithmetic (RSA, DSS), elliptic curves, DES, AES;

• Hash functions barely feasible

• Recent progress on putting AES on RFID tag

RFID is the Barcode of the Future

Barcode RFID

Line-of-sight reading• Reader must be looking at the barcode

Specifies object type• E.g., “I am a pack of Juicy Fruit”

Reading by radio contact• Reader can be anywhere within range

Specifies unique object id• E.g., “I am a pack of Juicy Fruit #86715-A”

Fast, automated scanning(object doesn’t have to leave

pocket, shelf or container)

Can look up this objectin the database

Static Data•No cryptographic operations possible

“Write Capabilities” • Products carry updated info as they move through the supply chain

Commercial Applications of RFID

Physical-access cards Inventory control

• Gillette Mach3 razor blades, pet tracking Logistics and supply-chain management

• Track a product from manufacturing through shipping to the retail shelf

Gas station and highway toll payment Libraries Euro banknotes

The consumer privacy problem

…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

Wig serial #A817TS8

Risks

Personal privacy

• I’ll furtively scan your briefcase and learn how much cash you are carrying and which prescription medications you are taking …

Corporate espionage : Privacy is not just a consumer issue

• Track your competitor’s inventory Skimming: read your tag and make my own

• In February, JHU-RSA Labs team skimmed and cloned Texas Instruments’ RFID device used in car anti-theft protection and SpeedPass gas station tokens

Blocking Unwanted Scanning

FARADAY CAGE•Container made of foil or metal mesh, impenetrable by radio signals of certain frequencies

•Invitation to Shoplifters•Maybe works for a wallet, but huge hassle in general – locomotion difficult

Blocking Unwanted Scanning (Contd.)

“KILL” tag after purchase• Special command permanently de-activates tag after the product is purchased

•RFID tags are much too useful in “live” state… Disables many futuristic applications.

Futuristic 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

Recycling• Plastics that sort themselves

Consumers will not want their tags “killed,” but should still have a right to privacy!

Blocking Unwanted Scanning (Contd.)

The “BLOCKER TAG”Blocker simulates all (billions of) possible tag serial numbers!!

1,2,3, …, 2023 pairs of sneakers and…(reading fails)…

How does blocker tag work?

When the reader sends a signal, more than one RFID tag may respond: this is a collision• Reader cannot accurately read information from more than one tag at a time• Example: every tagged item in a supermarket cart responds to the cashier’s

RFID reader

“Tree-walking” protocol for identifying tags recursively asks question:• “What is your next bit?”

Blocker tag always says both ‘0’ and ‘1’! • Guarantees collision no matter what tags are present• To talk to a tag, reader must traverse every tree path

• With 128-bit IDs, reader must try 2128 values – infeasible!

To prevent illegitimate blocking, make blocker tag selective (block only certain ID ranges)• E.g., blocker tag blocks all IDs with first bit=1• Items on supermarket shelves have first bit=0

• Can’t block tags on unpurchased items (anti-shoplifting)• After purchase, flip first bit on the tag from 0 to 1

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

000 001 010 011 100 101 110 111

00 01 10 11

0 1

?

Example: Supermarket Cart

000 001 010 011 100 101 110 111

prefix=0

prefix=00 prefix=01

prefix=10 prefix=11

prefix=1

1. Prefix=“empty”

Next=0Next=1

Next=1

Collision!

1a. Prefix=0

Next=0

No collision

2. Prefix=00

1b. Prefix=1

2. Prefix=11

No collision

Next=1

3. ID=001

Talk to tag 001

No collision

Next=1

Next=1

Collision!

Next=1

Next=0

3a. ID=110

Talk to tag 110

3b. ID=111

Talk to tag 111

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”

=?

Hash Locks

Reader RFID tag

Stores key; hash(key) for any tagUnique key for each tag

Stores metaID=hash(key)

Goal: authenticate reader to the RFID tag

[Rivest, Weis, Sharma, Engels]

“Who are you?”

metaID

key

“My real ID is…”

Compute hash(key) andcompare with stored metaID

Why is this not a perfect solution?

Analysis of Hash Locks

Relatively cheap to implement

• Tag has to store hash implementation and metaID Security based on weak collision-resistance of hash

function metaID looks random Problem: tag always responds with the same value

• Attacker can track the same tag from place to place even if he cannot learn its real ID

Randomized Hash Locks

Reader RFID tag

Stores its own IDk

[Weis et al.]

“Who are you?”

R, hash(R,IDk)

“You must be IDk”

Compute hash(R,IDi) for every

known IDi and compare

Stores all IDs:ID1, … ,IDn

Generate random R

Goal: authenticate reader to the RFID tag

Analysis of Randomized Hash Locks

Tag must store hash implementation and pseudo-random number generator

Secure against tracking because tag response is different each time

Reader must perform brute-force ID search

• Effectively, reader must stage a mini-dictionary attack to unlock the tag

Alternative: use a block cipher

• Need a very efficient implementation of AES

External re-encryption approach

Suggested for RFID-embedded banknotes privacy protection

Banknote tag serial numbers are encrypted with a law enforcement public key

Periodic re-encryption to reduce the linkability of different appearances of a given tag.

Resources limited on tag, so re-encryption done by external agents, usually the reader

References

The material covered in the slides hasbeen taken from : RFID Security and Privacy :

http://www.google.co.in/url?sa=U&start=1&q=http://www.cs.utexas.edu/~shmat/courses/cs378_spring05/&e=9797

RFID: Security and Privacy for Five-Cent Computers : http://www.rsasecurity.com/rsalabs/staff/bios/ajuels/publications/five_cent/RFID_five%20cent.ppt

Questions ?