David Molnar, David Wagner - Authors Eric McCambridge - Presenter

RFID = Radio Frequency Identification  Microchips with antennae affixed to objects  Powered by radio waves emitted by reader  Communicates ID number to reader (and possibly other information)

 Corporate Supply Chain Originally designed for fast inventory checking Quickly identify all of the items in a certain bin  Enhanced Drivers License and Passports Recent research from UW  K. Koscher, A. Juels, T. Kohno, and V. Brajkovic

 RFID tags on individual books (and other items)  Readers (exit sensors) placed at exit

Privacy Questions  Hotlisting: Who is reading this book?  Tracking: What is this person reading?  What people are reading the same books as this known terrorist?  Can we prevent people from checking out this book?

 Bibliographic Database Each book has a unique ID that is an index in the library’s database Database RFID

 Status stored on tag “Security Bit” = Is this book checked out? Set on each check-in/check-out RFID Then… RFID You’re checked out! I’m checked out!

 Bibliographic Database Fast enough?  Status on tag Denial of service (write-lock) Easy to fake (not addressed)  Both - Privacy Can identify individual books by their RFID number

 Can easily identify books by the data on their RFID tag Bibliographic DB can hide book’s title, but can identify individual copies Even hiding RFID number, unique collision ID is easy to get with off-the-shelf readers

 Randomized Transaction IDs Book has randomized, separate ID when it is checked out  Password Encryption via One-Time Pad Channel from tag to reader much harder to eavesdrop than reader to tag so… Pad is sent (in cleartext) to exit sensor by tag  Private Authentication Rest of this paper

 Tags are leaves in a balanced binary search tree  Edges of tree are shared secrets Generated uniformly at random  Traverse tree by finding which secret tag knows  O(log n) storage on tag  O(log n) work for reader

 Previous solution is O(k * log n) work where k is branching factor  Want O(k + log n) work:  How does this work? Identify the tag in the first phase: determine which branch to take Follow that branch

 Demonstrations of attacks Not as important – clear that these attacks are possible in the architectures they describe  Implementation of protocol Will this fit on a small, low-power RFID tag? Can the protocol be executed quickly enough that it works as people walk by exit sensors?