1. Selective Blocking of RFID Tags for Consumer Privacy
Ari Juels and Ronald L. Rivest and Michael Szydlo
Presented by Aviram Shmueli
4/22/2019
Selective Blocking of RFID Tags

2. Selective Blocking of RFID Tags
RFID – What is it?
RFID – Radio-Frequency Identification
RFID implementation consists of the following three parts:
Tag (small integrated circuit attached to an antennae)
Tag reader
Database & software
Tag holds a unique serial number which identifes the item it attached to
4/22/2019
Selective Blocking of RFID Tags

3. Selective Blocking of RFID Tags
RFID Uses
Retail & Distribution
Automated Checkout
Keyless Entry
Theft Detection
Pet Identification
Logistic Assets
4/22/2019
Selective Blocking of RFID Tags

4. Selective Blocking of RFID Tags
RFID Vs. Barcode
Barcode
RFID
Optical technology
RF technology
Line of sight only
Non line of sight
Read only
Read only or read/write capable
Smaller range (few cm)
Longer range (few meters)
Can carry data (2D)
Can carry more data
Not reusable
reusable
Sensitivity to dust, moisture and packaging
Insensitivity to enviromental factors
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Selective Blocking of RFID Tags

5. Selective Blocking of RFID Tags
RFID Benefits
More information
Individual item data & tracking
Small
As small as 0.4mm x 0.4mm
Ability to be embedded in almost every product
Fast
Data retrieval done in miliseconds
No contact
Cheap
0.05$/unit
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Selective Blocking of RFID Tags

6. Selective Blocking of RFID Tags
RFID Tag Attributes
Active RFID
Passive RFID
Tag Power Source
Internal to tag
Energy transferred using RF from reader
Tag Battery
Yes No
Required signal strength
Very Low
Very High
Range
Up to 100m
Up to 3-5m, usually less
Multi-tag reading
1000’s of tags recognized – up to 100mph
Few hundred within 3m of reader
Data Storage
Up to 128 Kb or read/ write & search
128 bytes of read/write
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Selective Blocking of RFID Tags

7. Selective Blocking of RFID Tags
Passive RFID Tags
Example: passive tags in
retail security applications
Tag contains antenna and a small chip
Tag is powered by the electromagnetic field generated in doorways, reflecting back a weak signal containing data
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Selective Blocking of RFID Tags

8. RFID Drawback – Threat to Privacy
RFID technology faces a clear potential for privacy violations
Location tracking
Belongings tracking
Ability to cross information with databases containing personal data
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Selective Blocking of RFID Tags

9. The “Kill Tag” approach
Solution:
“Kill” RFID tag upon purchase
No purchased goods would contain active RFID tags
Not Perfect:
Returned products
RFID receipts
Indentification of food in the refrigarator
Business cards
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Selective Blocking of RFID Tags

10. 2. The Faraday Cage approach
Solution:
Protecting an RFID tag by a metal container
Container is impenetrable by radio signals
Not Perfect:
Objects which can’t be placed in containers:
Clothing
Human beings
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Selective Blocking of RFID Tags

11. 3. The Active Jamming Approach
Solution:
Carrying a device that broadcasts radio signals
Device blocks/disrupts the operation of any nearby reader
Not Perfect:
May disrupt all nearby RFID systems, even those in legitimate application
Dummy, Crude and brutal way
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Selective Blocking of RFID Tags

12. Selective Blocking of RFID Tags
4. The “smart” Approach
Solution:
When tag is locked it’s given a value y.
Tag is unlocked by presenting a PIN value x
such that h(x)=y, where h is a one way has function
Not Perfect:
Tracking tags through their y value
Uncomfortable management
Small budget
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Selective Blocking of RFID Tags

13. The Tree-Walking Singulation Algorithm
Used by the RFID-tag reader
Identifies serial numbers of nearby tags (usually 64,96,128 bits long)
Based on a DSF of a binary tree
Iniation: Assumes a subtree to be the starting point.
Queries tags lying in the corresponding subtree:
Tags reply:
‘0’ – if lies in the left subtree
‘1’ – if lies in the right subtree
Collision – occurs when tags broadcast simultaneously ‘0’ and ‘1’
When Collision is detected, tag reader recurses beginning in the left child
Outputs list of the ID numbers of all tags within range
Complexity = ?
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Selective Blocking of RFID Tags

14. The Tree-Walking Singulation Algorithm
001
011
110 1 00 01
010
100
101
111
000 10 11
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Selective Blocking of RFID Tags

15. Selective Blocking of RFID Tags
What is a Blocker Tag?
Privacy Protection
Performs a “Passive Jamming”
Interferes with the tree-walking singulation protocol
Simulates the full spectrum of possible serial numbers for tags
Forcing reader to sweep a full space of all possible tags
DoS attacks?
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Selective Blocking of RFID Tags

16. Selective Blocking of RFID Tags
Blocker Tag – type 1
Universal Blocker
Simultaneously broadcasts both ‘0’ and ‘1’
Creates a forced collision
Tag reader must explore the all tree
Exploring tree in depth 128 would never end
Blocks reading of all tags
Lack of flaxiblity
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Selective Blocking of RFID Tags

17. Selective Blocking of RFID Tags
Blocker Tag – type 2
Selective Blocker
Blocks only a certain zone (subtree)
Simultaneously broadcasts both ‘0’ and ‘1’ only to queries which match certain condtions
Use of regular expressions
Reader might be stuck in a restricted subtree
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Selective Blocking of RFID Tags

18. Selective Blocking of RFID Tags
Blocker Tag – type 3
“Polite” Blocking
Involves protocol extension
Several options
New query: “Is this subtree blocked?”
Policy declaration
Enables flexible selective blocking of any node in the tree
Defining privacy zones
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Selective Blocking of RFID Tags

19. Malicious Use of Blocker Tag
Universal blocker
Total DoS
Simulation of actual tags
Actual tags may not be distinguished
Attacking the tag-reader software
Gain control over the tag-reader software
Gain access to the system DB
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Selective Blocking of RFID Tags

20. Selective Blocking of RFID Tags
Privacy Zone
Consists of a restricted range of tag serial numbers targeted for protection
Once enteres privacy zone, reader is distrupted by the blocker-tag
While reader remains outside the privacy zone, blocker-tag is inactive
Enables transfering serial numbers from one zone to another
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Selective Blocking of RFID Tags

21. Selective Blocking of RFID Tags
Glance to the future
Clothing and personal appliances are marked with “zone-one” prefix
Groceries are marked with “zone-one” prefix
Alice might carry a “zone-one” blocker tag in her wrist-watch
On groceries purchase, Alice is given “privacy stickers” carrying “zone-two” blocker tags
In her Car, Alice uses a blocker tag of all the possible zones
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Selective Blocking of RFID Tags

22. Selective Blocking of RFID Tags
Conculsions
RFID tags are supposed to enormously widespread in the following years
Usage of RFID technology raises potential for private threat
Blocker tag approaches intend to significally reduce this threat
Blocking is done “universally” or “selectively”, enabling defining “private zones”
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Selective Blocking of RFID Tags

23. Selective Blocking of RFID Tags
Thank You
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Selective Blocking of RFID Tags

24. Selective Blocking of RFID Tags
Home Assignment
Describe the tree-walking singulation protocol.
Describe the complexity of traversing through the all tree, using K (tree depth) and N (number of tags present).
Name one advantage and one disadvantage of any of three mentioned blocking methods
In your opinion, which of the proposed blocking methods should be adapted?
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Selective Blocking of RFID Tags