The Blocker Tag: Selective Blocking of RFID Tags for Consumer Privacy

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The Blocker TagSelective Blocking of RFID Tags
forConsumer Privacy

• Ari Juels, Ronald Rivest, and Michael Szydlo
• ACM CCS, October 2003
• Presented by Himanshu Pagey
• CDA 6938
• 04/03/2007

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• Content of this presentation has been
  adapted/taken from RSA Labs presentation slides
  for this paper
• http//www.rsa.com/rsalabs/staff/bios/ajuels/publ
  ications/blocker/blocker.pdf

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RFID Grand Vision Next Generation Bar Codes

• Line of sight
• Identifies a product.
• Radio Contact ( Fast automated scanning)
• Uniquely identifies a product ( Provides a
  pointer to an entry in database)

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Constraints / Privacy Concerns

• Few Thousand Gates
• No Cryptographic function available.
• Static read / Write functions

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Commercial Applications

• Supply Chain Inventory tracking
• Anti counterfeiting
• Parenting logistics (RFID bracelets for children
  in water park)
• Maintaining shelf stocks in retail environment
• Gillette Mach 3 Razor blades
• Product Recalls

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Reference http//www.rsa.com/rsalabs/staff/bios/a
juels/publications/blocker/blocker.pdf
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Approach 1 Faradays Cage
Reference http//www.rsa.com/rsalabs/staff/bios/a
juels/publications/blocker/blocker.pdf
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Approach 2 Kill Tags
Reference http//www.rsa.com/rsalabs/staff/bios/a
juels/publications/blocker/blocker.pdf
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Usefulness of RFID tags

• Product Return
• Physical Access Control
• Theft Protection
• Intelligent microwaves
• For the success of these applications the
  RFID tags cannot be killed.

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Smart Applications

• Smart Microwaves . Ovens that know how to cook
  pre-packaged food items.
• Smart Refrigerator that can recognize expired
  items and create shopping lists.
• Closets that can tally the contents.
• Airline tickets that indicate your location in
  the airport
• Function Creep many more uses unimagined or
  unimaginable

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Consumer Backlash

• Walmart Smart shelf project cancelled.
• Benetton RFID plans withdrawn
• Campaigns against RFID usage
• NoCards.org
• BoycottGillette.com
• BoycottBenetton.com
• CASPIAN (Consumers Against Supermarket Privacy
  Invasion and Numbering)

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Blocker Tag
Reference http//www.rsa.com/rsalabs/staff/bios/a
juels/publications/blocker/blocker.pdf
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Blocker Tag
Reference http//www.rsa.com/rsalabs/staff/bios/a
juels/publications/blocker/blocker.pdf
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Tree Walking protocol
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Basic Working

• Reader recursively asks the tags
• What is your next bit?
• The tag replies 0 and 1 both
• Reader thinks that all the possible tags are
  present.
• Reader stalls as number of possibilities are
  huge.
• Possibilities are at least 264 in most basic
  systems.
• This is universal blocker tag

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Reference http//www.rsa.com/rsalabs/staff/bios/a
juels/publications/blocker/blocker.pdf
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Selective Blocking

• Blocker Tag can block tags within certain zones.
  Such zones are privacy zones
• Tags can be moved between zones.
• For Example
• The blocker tag block tags with leading 1
• Retail store items have tags with prefix 0
• At check out counter the leading bit is flipped
  from 0 to 1

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Blocking with Privacy Zones
Reference http//www.rsa.com/rsalabs/staff/bios/a
juels/publications/blocker/blocker.pdf
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Polite Blocking

• Singulation protocol can be revised to make it
  work efficiently with the blocker tags.
• Aim of the blocker is to keep functionality
  active when desired by the owner.
• If the reader tries to read the tag it will
  stall.
• The tag informs the reader about its presence.
• Before asking for next bit the protocol asks Is
  the sub tree rooted at this node blocked

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Leading bit is flipped to 1 and a blocker tag
is provided to the customer
Tags contain leading 0 bit
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Strengths / Main Contribution

• Low Cost Implementation
• Ordinary consumer RFID-tag may not need to be
  modified at all.
• Blocker tags can be cheap. ( Around 10 cents per
  tag)
• Implementation is not resource intensive. Need to
  manage passwords for authorizing change to
  privacy zones

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Weakness

• Reader can probably sense the existence of two
  tags transmitting at close proximity and can
  still traverse the privacy zone sub tree.
• Consumers must take the step of protecting their
  own privacy (opt-out policy). The consumers
  might prefer an opt-in Policy

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Suggested Improvements

• Research an Opt in approach like soft blocking.

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• Questions ?