Privacy in Library RFID

guineanscarletElectronics - Devices

Nov 27, 2013 (3 years and 10 months ago)

85 views

Privacy in Library RFID

Attacks and Proposals

David Molnar

David Wagner

{dmolnar, daw}@eecs.berkeley.edu

Privacy in Libraries


Must protect what patrons are reading


Library only source of info for many


FBI Library Awareness Program


1973
-
1988, official policy to monitor “suspicious”
persons’ reading habits


Library privacy laws passed as backlash


Even with PATRIOT act, need court order


Privacy adversaries not limited to FBI


Marketers, Scientologists, pick your favorite…



RFID & Library Overview


RFID = Radio Frequency IDentification


One RFID tag per book


Each RFID tag has ``bar code” ID number


Unique to each book, may identify library


Exit gates read RFID for anti
-
theft


13.56MHz passive RFID


ISO 15693, Checkpoint, TAGSYS C220


Read range depends on antenna size


Deployed in Oakland, Santa Clara, 130+

Why RFID?


Speedy self
-
checkout


reduce library employee RSI (carpal tunnel)


Security devices


ensure checkout occured


Inventory Tracking

Pictures courtesy

Santa Clara City Library

Privacy and Ubiquitous
Readers


Read range not whole privacy story


Even full in
-
view readers can be problem


Scan at airport security, events, etc.


Like metal detectors now


Not clear what read or how used


Readers easy to camouflage


RFID reader looks like store anti
-
theft gate

Library RFID Architecture

Library database


No authentication between reader and tag


Database maps bar code


(title, status)

Bar code

Attack: Book Scanning


Can Mallory scan me and tell what I am
reading?


No reader


tag authentication


Anyone can read tag data


Most deployments data limited to bar code


Some vendors suggest more


Need library database


In CA, database protected by law


Varies by state

Attack: Hotlisting and Profiling


Hotlisting


楳⁢潯欠潮⁳灥p楡氠汩l琿


It’s real


FBI and almanacs


Profiling


bar code prefix identifies library


Is library in predominantly minority area?


Bar code never changes so hotlisting easy


Walk into library, read bar code


See the book again, recognize book


Does not need library database

Attack: Book Tracking


Bar code never changes


Can link different sightings


Track book movement


Spatial movement


Combine w/video for person
-
to
-
person


“This person checked out same book as
terrorist”


Does not need library database

“Security Bit” Denial of Service


RFID used for anti
-
theft


Some vendors store “security bit” on tag


Security bit = checked out/not checked out


Bit re
-
written each checkout


ISO 15693 tags have “write, then lock”


No way to unlock data, no password on lock


Adversary can lock security bit data page


Can’t change security bit


tag useless

Collision Avoidance and
Privacy


Collision avoidance protocols identify tag


Example: ISO 15693 mandates MFR ID






Read passwords,changing ID,etc. don’t help


Privacy requires attention to all layers


Mask

Does mask match MFR ID?

Respond if yes

RFID Limitations


RFID powered only when near reader


No precomputation, no caching


RFID have few gates (< 5,000 for security)


Randomness difficult on RFID


“Cryptography” extremely hard on RFID


Best we can do is a few XOR


Future generation tags focus on price, not on
security features


Problem: Private
Authentication








Reader does not know tag ID


Authentication must preserve privacy


Privacy and authentication in tension


Random Transaction IDs


Required: rewritable tags


Attacker model: outside the library


On checkout


Obtain random #
r


Write (
r
,
D
) to DB


Erase
D

& Write
r

to tag


On checkin


Use
r

to lookup
D


Write
D

to tag

Attacks Against Random IDs


Tracking


Possible


Only for checkout duration


Hot
-
listing


Not Possible


Comparison
-
based


Not possible

Password Enhancement


Eavesdropping


Not the same in the two channels


Tag to Reader is Harder


Hello

r

cmd,
p
=
r



s

Good and Bad of Passwords


Good


low computation cost


s

remains secure (info
-
theoretically!)


r
is independent of book info


cannot be tracked


Bad


Requires randomness on tag

Private Authentication


Every tag has a secret


DB has all (
secret
, ID) pairs


Basic ID


Reader sends a nonce


Tag sends new nonce


Tag sends ID


f(
s
, 0, nonce 1, nonce 2)


Reader checks the whole DB


Problems?

Tree
-
based


Set it all up as a binary balanced tree


log(n) rounds


Check if the secret is on the left or right


Get down to a single leaf


Advanced version


1 million tags


168 bits of communication

Summary


Library RFID is here now


All today’s technology has privacy flaws


Privacy is achievable efficiently


Work still ongoing

Acknowledgements


Many, many people to thank!


In no particular order:


Peter Warfield, Karen Duffy (Santa Clara City Library), Karen Saunders (Santa
Clara City Library), Susan Hildreth (San Francisco Public Library), Al
Skinner (Checkpoint), Paul Simon (Checkpoint),Doug Karp(Checkpoint),
Rebekah E. Anderson (3M), Jackie Griffin(Berkeley Public Library), Elena
Engel (BPL), Alicia Abramson(BPL)Lee Tien (Electronic Frontier
Foundation), Dan Moniz (EFF), Laura Quliter (Boalt Hall School of Law, UC
-
Berkeley), Jennifer Urban(Boalt), Nathaniel Good (SIMS), Samuelson
Technology and PolicyLaw Clinic at Boalt Hall School of Law, Elizabeth
Miles (Boalt),John Han (SIMS), Ross Stapleton
-
Gray, Eric Ipsen, Oleg
Boyarsky(Library Automation/FlashScan), Laura Smart (Library
RFIDWeblog/Cal State Pomona), Craig K. Harmon (ISO 18000
committee),Justin Chen (SVCWireless RFID SIG), Steve Halliday(ISO 18000
committee), Zulfikar Ramzan (NTT DoCoMo), Craig Gentry (NTTDoCoMo),
Hoeteck Wee, Matt Piotrowski, Jayanth Kumar Kannan, Kris Hildrum,
David Schultz, and Rupert Scammell(RSA Security).

Questions?