1. The Blocker Tag: Selective Blocking of RFID Tags for Consumer Privacy A. Juels, R. L. Rivest, and M. Szydlo 8th ACM Conference on Computer and Communications Security, pp. 103-111. ACM Press. 2003. Presented by: Sean Mondesire

2. 3/30/2006The Blocker Tag2 Contributions o Blocker Tags: o Protects consumer privacy o Relatively inexpensive o Proves the RFID Bill of Rights and practical tags can coexist

3. 3/30/2006The Blocker Tag3 Agenda o RFID Tags o Security Issues o Previous Work o Blocker Tags Privacy Protection Malicious Blocker Tags o Critique

4. 3/30/2006The Blocker Tag4 RFID Tags o Simple Radio-Frequency Identification Tags Passive: Battery-less Contain an assigned serial number Can be modified o Replacement for the barcode Cost about 5 cents No more laser scanning Consumers can use the benefits

5. 3/30/2006The Blocker Tag5 Security Issues o Eavesdroppers Gather what items are in your possession Privacy Violation Examples o Dress size o Medication o Amount of money in wallets o Petty Thieves Modify serial numbers in store Deactivate tags before purchase

6. 3/30/2006The Blocker Tag6 Previous Work o “Kill Tag” o Faraday Cage o Active Jamming o “Smart” RFID Tags Hash-Locks Re-encryption

7. 3/30/2006The Blocker Tag7 Tree-Walking Singulation o Singulation Reader processes one tag at a time o Tree-Walking Singulation Algorithm Recursively signal tags with next prefix Tag with prefix respond with next prefix 01 00011011

8. 3/30/2006The Blocker Tag8 Blocker Tags o Goal: o Protect the privacy of consumers affordably o Motivation: o Guaranteed privacy will push the use of RFID tags o How They Work o Universal Blocker: For every signal send 0 and 1 o Selective Blocker: Block a subset of tags

9. 3/30/2006The Blocker Tag9 Privacy Protection Tool o Selective Blocker: Forces readers to signal nonexistent and existent tags Readers cannot guarantee tags are in the vicinity Hides tags with false signals o Supermarket Example: Shelved items start with 0 Purchased items tags set to 1 Sticker of a blocker tag placed on item’s tag (blocks 1’s)

10. 3/30/2006The Blocker Tag10 Malicious Blocker Tags o Blocker tags that do not respect the privacy zones Blocker signaling 0’s in previous example o Universal blockers are malicious o DOS attacks on readers Universal blockers: Readers signal all possible serial numbers Selective blockers: Simulate actual tags that should not be scanned at that time

11. 3/30/2006The Blocker Tag11 Strengths o Inexpensive RFID to reply to signals Less than 10 cents to manufacture o Satisfies the RFID Bill of Rights o Simple to implement Create tag that returns 0 or 1 when ever signaled

12. 3/30/2006The Blocker Tag12 Weaknesses o Can force DOS on reader Encourages nonsense broadcasts o Requires additional RFID tags Forces consumers to have blocker tags to guarantee privacy o Many unanswered questions: What if malicious blocker tags were left throughout a store? Thieves can swap tags easier than barcodes

13. 3/30/2006The Blocker Tag13 Areas of Improvement o Improve inefficiencies placed on the Reader Universal Blocker impractical Limit blocking capabilities o Incorporate blockers within each tag Cost for addition registers should be comparable to having separate blockers

14. 3/30/2006The Blocker Tag14 Related Work o RSA Laboratories Inventors of RSA public-key cryptosystem Focus on RFID privacy and security o Soft Blocking o Encryption in RFID o RFID chips can carry a virus Amsterdam’s Free University RFIDs can return data to infect a reader’s DB Can spread to other tags

15. 3/30/2006The Blocker Tag15 Contributions o Protects consumer privacy Readers can’t pinpoint existing tags o Relatively inexpensive About 5 cents for one antennae At most 10 cents per blocker o Proves the RFID Bill of Rights and practical tags can coexist No sacrifices on consumer rights

16. 3/30/2006The Blocker Tag16 References o Juels, A., Rivest, R. L., and M. Szydlo, “The Blocker Tag: Selective Blocking of RFID Tags for Consumer Privacy,” 8th ACM Conference on Computer and Communications Security, pp. 103-111. ACM Press. 2003. o Reuters, “Scientists: RFID Chips Can Carry a Virus”, http://www.cnn.com/2006/TECH/ptech/03/15/rfid.vir us.reut/index.html, CNN.com, March 15, 2006 o RSA Laboratories, http://www.rsasecurity.com/, March 28, 2006.