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

• www.komonews.com/news/local/33205899.html• www.rsa.com/rsalabs/node.asp?id=3557

RFID tags on individual books(and other items)

Readers (exit sensors) placed at exit

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

DatabaseDatabaseRFIDRFID

Status stored on tag• “Security Bit” = Is this book checked out?• Set on each check-in/check-out

RFIDRFIDThen

…RFIDRFID

You’re checked

out!

You’re checked

out!

I’m 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?