1. RFID SECURITY

2. How Does RFID Work? Tags (transponders) Reader (transceiver) Database
02.3DFEX4.78AF51
EasyToll card #816
Radio signal (contactless)
Range: from 3-5 inches to 3 yards
Tags (transponders)
Attached to objects, call out their (unique) name and/or static data on a special radio frequency
Reader (transceiver)
Reads data off the tags
without direct contact
Database
Matches tag IDs to
physical objects

3. Asymmetric channels Range of Reader (Forward Channel) ~100 m
TAG
EAVESDROPPER
~5 m
Tag’s Range (Backward Channel)

4. Applications Tracking/Identification
Library Books
Children
Pets
Auto Parts
Inventory management in a Supply Chain
Contactless Smart Cards

5. A Generic Supply Chain Retailers Wholesalers Manufacturers
Suppliers
Manufacturers
Wholesalers
Retailers
goods, invoices
Purchase orders, payments
Supply web (retail customers not shown)

6. Key Decisions When to order How much to order From whom to order
As order quantity increases, holding cost increases
As order quantity decreases, stockout cost increases
From whom to order

7. The Problem - Motivation
Basic problem with RFID tags
Can be remotely scanned
Respond to query by any reader
This leads to security and privacy risk
Resource constraints
Limited power and computing resources
Hence classical cryptographic mechanisms not feasible
The RFID security challenge
How to obtain maximum security with almost no resources?

8. The Problems of Privacy and Security
RFID privacy concerns the problem of misbehaving readers harvesting information from well-behaving tags.
Risks :
Leakage of personal information (prescriptions, brand/size of clothes etc.).
Location privacy: Tracking the physical location of individuals by their RFID tags.
RFID authentication concerns the problem of well behaving readers receiving information from misbehaving tags, particularly counterfeit ones.
Risks:
Forgery
Sabotage

9. Cost and capability
The strength and flavor of proposed security solutions will depend on the allowed tag cost for different applications
50+ cent tags. Low-end tags will be 10 cent, 5 cent and 2 cent in about 5 years

10. Challenge
Tens of research ideas have been proposed in the past two years
Propose improvements over the existing privacy enhancing protocols for the extremely resource constrained RFID systems

11. Security Attacks Spoofing Denial of Service Man in the middle attack
Imitating the behavior of a genuine tag
Denial of Service
Man in the middle attack
Modify the response of the tag to the reader or vice versa
Replay Attack
Eavesdrop message from the tag (reader) & re-transmit the message to the legitimate reader (tag).
Traffic Analysis
Monitoring of comm. between reader & tag allows adversary to perform traffic analysis & generate statistical data.

12. Security and Privacy Requirements
Anonymity
Tag output should not give idea about ID
Untraceability
Tag output should be varying
Indistinguishibility
Tag output should be truly random, i.e. variation should not be predictable
Forward Security
Adversary should not be able to associate the current output with past output
Mutual Authentication
Tag-to-reader and reader-to-tag authentication

13. Backend Requirements Efficiency and scalability Flexibility
Order of computation/precomputation required as a function of number of tags
Flexibility
Changes required with addition/removal of tags

14. Hash Lock Reader RFID tag Goal: Authenticate reader to the RFID tag
[Rivest, Weis, Sharma, Engels]
Goal: Authenticate reader to the RFID tag
Reader
“Who are you?”
RFID tag
metaID
key
Compute hash(key) and
compare with stored metaID
“My real ID is…”
Stores metaID=hash(key)
Stores key; hash(key) for any tag
Unique key for each tag

15. Hash Lock Analysis PROS CONS
Relatively cheap to implement : Tag has to store hash function implementation and metaID
Security based on weak collision-resistance of hash function
Scalable due to low key look-up overhead
CONS
Constant tag output – enables traceability
Motivates Randomization
Too many messages/rounds
Requires reader to know all keys

16. Randomized Hash Lock Reader RFID tag
[Weis et al.]
Goal: Authenticate reader to the RFID tag
Reader
RFID tag
“Who are you?”
Generate random R
R, hash(R,IDk)
Compute hash(R,IDi) for every
known IDi and compare
“You must be IDk”
Stores its own IDk
Stores all IDs:
ID1, … ,IDn

17. Randomized Hash Lock Analysis
PROS
Randomized response prevents tracking
Tag needs to store hash implementation and pseudo-random number generator
CONS
Inefficient brute force key look-up
No Forward security
Motivates updating tag ID on each read
Security Flaw - Adversary can impersonate tag by learning a valid tag response.

18. OSK Scheme
[Ohkubo, Suzuki and Kinoshita]
Goal: Enable reader to identify the RFID tag, change tag identifier on each read
Database
Reader
Tag
Query
Ai=G(Si)
Ai=G(Si)
Compute Hash Chain
Si+1=H(Si)
Tag ID

19. OSK Analysis Motivates reducing computation time at reader/backend
PROS
Different random like values on every read operation prevents tracking
Forward Security ensured due to one way hash property
Tag needs to store only 2 hash implementations, hence low cost
Minimal number of transmissions
CONS
Not scalable for large scale applications due to brute force search
Motivates reducing computation time at reader/backend
Susceptible to DoS attacks
May lead to problem due to hash collisions.

20. Summary
RFIDs have many useful applications related to tracking and identification
But there are some important issues of security and privacy
Small number of gates for S/P makes the design of such protocols challenging
Tens of schemes proposed for security/privacy but subtle drawbacks with many of them. Much more work needed in this area