path: root/2008/openpcd_openpicc-cluc2008/librfid.tpp

--author Harald Welte <laforge@gnumonks.org>
--title RFID Protocols, librfid
--date 17 Apr 2008
Starting with November 2005, the German federal government has started to issue
epectronic passports with RFID interface.  All other EU member states will have
to issue such passports no later than January 2007.  Only Switzerland seems to
have a reasonable attitude by giving their citizens a choice.

This presentation covers technical background about the RFID technology, the ICAO MRTD specification, and the authors' efforts to develop a free software stack to use Linux to communicate with those passports.
--footer This presentation is made with tpp http://synflood.at/tpp.html

--newpage
--footer RFID Potocols and librfid
--header Overview
Introduction into RFID
	What is RFID
	Components of RFID System
	Protocols and Standards
	Security Issues
librfid - A free software RFID stack
	Data Structures
	Protocol Stack
	Interaction with OpenCT

--newpage
--footer RFID Potocols and librfid
--header Introduction into RFID
Definition of term RFID
	Radio Frequency IDentification
	
RFID is one of the recent buzzwords in lots of industries, such as
	transportation
	retail sector
	governments

Like most buzzwords, it's not very clearly defined.  There is no such thing as "the RFID System. There are lots of different Systems, some standardized, most proprietary.  Each of them uses it's own frequency, modulation, encoding and protocol combination.  Often, systems of multiple vendors can not be used interchangibly.

--newpage
--footer RFID Potocols and librfid
--header Components of an RFID system
Tag (Transponder)
	Serial Number Tags
		Replacement for EAN/UPC Barcodes
	WORM Tags
		Can be written once by Issuer
	Read/Write Tags
		Can be re-written many times
	Read/Write Tags with "passive" security
		Have state-machine based crypto for access control
	Cryptographic smartcards with RF Interface
		Like other crypto smartcards, just with RF interface

--newpage
--footer RFID Potocols and librfid
--header Reader
Readers (Coupling Device)
	Readers are always called readers, even if they can write ;)
	Usually connected to a host computer via RS-323, USB or alike
	Unfortunately no standard, for API, Hardware and/or Protocol :(
	Most applications are written to vendor-provided device-specific API's
	One exception: Readers for Smartcards with RF-Interface (use PC/SC)

--newpage
--footer RFID Potocols and librfid
--header RF Interface
The RF interface is the key attribute of any RFID system.
Parameters that determine the RF interface are
	frequency
	modulation
	operational principle

--newpage
--footer RFID Potocols and librfid
--header RF Interface
Magnetic Coupling
	used by many of todays RFID deployment
	rely on the magnetic coupling ("transformer") principle
	Tag/Transponder has a coil antenna to pick up RF-Field of Reader
	Power for Tag/Transponder is drawn from the magnetic field
	Common systems use 125kHz (old) or 13.56MHz (current)
	Operational range often small, since high magnetic field strengh needed

--newpage
--footer RFID Potocols and librfid
--header RF Interface
Backscatter
	Used by many RFID systems under current development
	Operate typically in UHF range (868 to 956 MHz)
	Use electric field of the reader, employ backscatter modulation
	Higher operational range (within tens of metres)

Surface Accoustic Wave
	SAW tags use low-power microwave radio signals
	Tag/Transponder converts it to untrasonic signals (piezo crystal)
	Variations of the reflected signal used to provide a unique number

--newpage
--footer RFID Potocols and librfid
--header Protocols and Standards
Apart from the various vendor proprietary protocols, there are some ISO standards
ISO 11784 / 11785
	Identification of Animals
	134.2kHz, magnetic coupling, load modulation, 4191 bps
ISO 14223
	Extension of 11784/11785 and allows for more data
ISO 10536
	"close coupling" smart cards, range up to 1cm
	Inductive or capacitive coupling at 4.9152MHz
	Never attained any significant market share
ISO 18000 series
	Current development of international "Auto-ID" standard
	Includes operation on 13.56MHz, 2.4GHz, 868/956MHz
	Not yet deployed

--newpage
--footer RFID Potocols and librfid
--header Protocols and Standards
ISO 14443
	"proximity coupling ID cards"
	Range of up to 10cm
	Two variants: 14443-A and 14443-B
	Both use 13.56MHz, but different parameters (see paper for details)
	Specifies physical layer, link-layer (anticollision)
	Specifies an optional transport level protocol (ISO 14443-4)
	Speed up to 848kbits/sec

ISO 15693
	"vicinity coupling", range up to 1m
	Like ISO 14443, operates on 13.56MHz, magnetic coupling
	Data rate 1.65kbits/sec or 26.48kbits/sec
	Because of long distance, very little power
	Therefore only used for passive tags

--newpage
--footer RFID Potocols and librfid
--header Protocols and Standards
ISO 14443-A Details
	Anti-Collision is based on binary search
	Manchester Encoding allows reader to detect bit collisions
	Reader can transmit bit-frames of variable length

	1. Reader sends REQA / WUPA
	2. All transpondesr in range will reply with their address (UID)
	3a. If there is no collision, send SELECT comamand on full UID
	3b. If there is a collision, transmit bit frame which forces bit of collision to 0 or 1
	4. Loop
	
--newpage
--footer RFID Potocols and librfid
--header Protocols and Standards
ISO 14443-B Details
	Anti-Collision is based on "Slotted ALOHA" protocol
	Based in probabilistic scheme
	Reader sends REQB/WUPB command with number of available slots
	Every transponder chooses it's own number (rnd() % slots)
	If there is a collision, we simply retry.

Result:
	Both 14443-A and 14443-B anti collision are subject to DoS
	"blocker tags" have already been demonstrated.

--newpage
--footer RFID Potocols and librfid
--header Protocols and (Non-)Standards
Mifare
	Mifare is a marketing term by Philips

	Mifare refers to a complete family of RFID systems, comprising 
		Transponders, Reader ASICs and a set of prorprietary protocols.
	Mifare Classic transponders (1k, 4k)
		are memory transponders with state machine based crypto
	Mifare Classic employs a proprietary stream cipher (CRYPTO 1) that 
		is implemented in both transponder and reader hardware
	Mifare Ultralight has no crypto, plain passive memory transponder
	Mifare transponders are segmented in blocks, every block has 
		it's own pair of CRYPTO1 access keys and permission management 

--newpage
--footer RFID Potocols and librfid
--header Closer look on Readers
There's a variety of readers for the 13.56MHz world
Usually they all use one of the (small number of) available ASIC's
Reader ASIC's integrate analog and digital part and have standard bus interface
End-User Reader products contain such an ASIC plus a microcontroller

Active Readers
	e.g. "Philips Pegoda"
	Run the RFID protocol stack on the microcontroller

Passive Readers
	e.g. "Omnikey CardMan 5121"
	Run the RFID protocol on the host system

Passive readers obviously provide higher flexibility and are cheaper.

--newpage
--footer RFID Potocols and librfid
--header Security Issues
Eavesdropping
	Channel from reader to tag can be easily sniffed (even > 10m)
	Channel from tag to reader is difficult (Author has managed 3m)

Denial of Service
	Anti-collision mechanism used to distinguish between multiple tags
	Using a "fake tag" you can create Denial of Service
	Products such as "blocker tags" have already been presented

Authenticity/Confidentiality
	None of the existing standards offers any kind of crypto
	Standards-compliant systems like passports use crypto at layer 5
	Lots of proprietary "closed algorithm" vendor products with questionable security


--newpage
--footer RFID Potocols and librfid
--header librfid - A Free Software RFID stack
The librfid project intends to provide a free software reader-side implementation of common RFID protocols such as ISO 14443 and ISO 15693

Various abstraction layers and plugin interface allows for later addition of new protocols an readers.

Optionally integrates with OpenCT.

--newpage
--footer RFID Potocols and librfid
--header librfid - A Free Software RFID stack
struct rfid_asic
	Contains all routines for a specific reader asic
	Currently only Philips CL RC 632 and Philips Pegoda (partially) supported
struct rfid_asic_transport
	A transport that gives access to the ASIC registers
struct rfid_reader
	A container for rfid_asic and rfid_asic_transport
struct rfid_layer2
	An anticollision protocol such as ISO 14443-3A/B
struct rfid_protocol
	A transport protocol such as ISO 14443-4

--newpage
--footer RFID Potocols and librfid
--header librfid - A Free Software RFID stack

Typical Protocol Stack
	rfid_protocol_stack
	CM5121 Reader
	CL RC632 ASIC
	PC_to_RDR_Escape transport
	USB-CCID driver of OpenCT
	libusb

--newpage
--footer RFID Potocols and librfid
--header librfid - A Free Software RFID stack
Application Interface

Native API
	librfid-specific API
	quite low-level
	requires application to know a lot about the stack

OpenCT, PC/SC, CT-API
	OpenCT integration provides PC/SC and CT-API for crypto smarcards
	Is currently under development

--newpage
--footer RFID Potocols and librfid
--header Electronic Passports
Electronic Passports (ePassports) are officially called MRTD
MRTD: Machine Readable Travel Document
Specifications by ICAO (International Civil Aviation Organization)
Basic idea 
	store passport data and additional biometrics on Transponder
	alternate storage methods such as 2D barcodes covered, too
	common standard for interoperability
	some features required, others optional (up to issuing country)

--newpage
--footer RFID Potocols and librfid
--header Electronic Passports
Organization of Data
	According to LDS (Logical Data Structure) specification
	Data is stored in DG (Data Groups)
		DG1: MRZ information (mandatory)
		DG2: Portrait Image + Biometric template (mandatory)
		DG3-4: fingerprints, iris image (optional)
	EF.SOD: Security Object Data (cryptographic signatures)
	EF.COM: Lists with Data Groups Exist
	All data is stored in BER-encoded ASN.1
		just think of all the ASN.1 parser bugs...
	DG2-DG4 are encoded as CBEFF (common biometric file format, ISO 19785)

--newpage
--footer RFID Potocols and librfid
--header Electronic Passports
Security Features
	Randomization of Serial Number
		Usually all ISO 14443 transponders have a unique serial number
		This serial number is part of the anticollision procedure
		Problem: Pseudonymized Tracking
		ICAO MRTD specs don't require unique serial number
		Therefore, some countries will generate random serial numbers

--newpage
--footer RFID Potocols and librfid
--header Electronic Passports
Security Features
	Passive Authentication (mandatory)
		Proves that passport data is signed by issuing country
		Inspection System verifies signature of DG's
		EF.SOD contains individual signature for each DG
		EF.SOD itself is signed
		Document Signer Public Key from PKD / bilateral channels
		Document Signer Public Key also stored on Passport (optional)
			Useful only if Country Root CA public key known

--newpage
--footer RFID Potocols and librfid
--header Electronic Passports
Security Features
	Active Authentication (optional)
		Verifies that chip has not been substituted
		Uses challenge-response protocol between reader and chip
		DG15 contains KPuAA
		KPrAA is stored in secure memory of the chip
		PPuAA is signed in EF.SOD

--newpage
--footer RFID Potocols and librfid
--header Electronic Passports
	Basic Access Control (optional, implemented in .de passports)
		Denies Access to the chip until inspection system is authorized
		Authorization is performed by deriving keys from MRZ
		MRZ_info
			nine digit document number
				in many countries: issuing authority + incrementing number
			six digit date of birth
				can be guessed or assumed between
			six digit expiry date
		16most significant bytes of SHA1-hash over MRZ_info is key
		3des keys used for S/M (ISO7816 secure messaging)
		

--newpage
--footer RFID Potocols and librfid
--header Electronic Passports
	Extended Access Control (optional)
		Prevents unauthorized access to additional bimetrics
		Similar to Basic Access Control, but different keys
		Not internationally standardized
		Implemented by individual states
		Only shared with those states that are allowed access


--newpage
--footer RFID Potocols and librfid
--header Electronic Passports
	Encryption of Additional Biometrics (optional
	The actual payload of the CBEFF

--newpage
--footer RFID Potocols and librfid
--header Electronic Passports
Public Key Hierarchy
	X.509 Certificates
	Every country operates it's own CA
	Document signer keys derived from CA root
	Document signer public keys are distributed publicly via ICAO PKD
	Everyone can verify

--newpage
--footer RFID Potocols and librfid
--header libmrtd - Free Software library for MRTD's
libmtrd provides functions for
	reading out and decoding data on MRTD
	verifying data stored on MRTD
	cryptograpy compliant with MRTD specs
		basic access control
		passive authentication
		extended access control (planned)

--newpage
--footer RFID Potocols and librfid
--header libmrtd - Free Software library for MRTD's
API towards the lower level (transport)
	PC/SC (to work with readers/drivers other than librfid)
	native librfid API
API towards the application
	not really finished yet, lots of flux

--newpage
--footer RFID Potocols and librfid
--header libmrtd - Free Software library for MRTD's
libmrtd status
	parsing functions for LDS
	parsing functions for DG1
	parsing functions for DG2 (CBEFF)
	basic access control
	still very much beta stage software
	contributors welcome
	no frontend application program

--newpage
--footer RFID Potocols and librfid
--header Further Reading

The slides
	https://svn.gnumonks.org/trunk/presentation/2005/rfid-0sec2005/
The paper
	https://svn.gnumonks.org/trunk/presentation/2005/rfid-lk2005/
librfid code
	https://svn.gnumonks.org/trunk/librfid/
libmrtd
	https://svn.gnumonks.org/trunk/libmrtd
the mailinglist
	librfid-devel@lists.gnumonks.org
	https://lists.gnumonks.org/mailman/listinfo/librfid-devel
ICAO MRTD homepage (includes all MRTD specs in PDF format)
	http://www.icao.org/