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- different types of RFID
- serial-number-only
- read/writeable memory
- read/writeable memory with authentication
- processor chip cards (like contact-based)
- physical/electrical characteristics
- old 125kHz systems
- current 13.56MHz systems
- ISO 14443-A
- ISO 14443-B
- ISO 15693
- both 125kHz and 13.56MHz are magnetic H-field systems
- reader provides strong magnetic field to provide power to PICC
- data from reader to PICC is modulated onto carrier.
- PICC uses load modulation to send back replies to reader
- ISO 14443
- 14443-1
- defines physical layer (e.g. field strength, ...)
- 14443-2
- 14443-3 A
- 100% ASK from reader to PICC
- binary search tree anticollision
- 14443-3 B
- 10% ASK from reader to PICC
- slotted aloha anticollision
- 14443-4
- also called T=CL
- datagram-based transport protocol
- handles retransmission, ack/nack
- optional signal strength signalling
- data rates between 106 and 848 kbps
- Mifare
- proprietary system by philips
- requires philips circuits in tag and reader
- authentication using two 40bit? keys
- proprietary encryption algoritm
- brute-force of 40bit not possible due to slow devices
- ISO 15693
- only used by tags, not by smart cards
- STm
- Legic
- Available readers
- generally based on either Philips or STM reader ASIC
- reader ASIC integrates analogue RF and digital part
- typically offer SPI and/or parallel bus interface
- host interface either serial or USB (planned: ethernet, see also
IETF working group on this subject)
- serial readers speak either proprietary protocol or sometimes
emulate serial contact-based readers for 14443-4 (T=CL)
- stupid readers
- only connect reader ASIC to host pc
- protocol stack implemented on host pc
- intelligent readers
- handle protocol stack in firmware of microcontroller in the
reader
- sometimes even parts of the application are embedded in the
reader firmware
- problem: often only support very specific
protocols/applications
- librfid
- implements 14443-1234 and 15693 stack
- has hooks for mifare and other proprietary RFID protocols
- implements fairly generic driver for Philips CL RC632 ASIC
- currently only supports Omnikey CardMan 5121
- currently only offers non-standard API for higher-level apps
- scheduled to provide OpenCT backend (OpenCT supports CT-API and PC/SC)
- Problems
- T=CL looks almost like a layer 4 network protocol, 14443 supports
operation of multiple PICC's simultaneously (by using CID
addressing). Therefore it looks like a master/slave network
protocol.
- Current API's for contact based cards (like PC/SC) cannot deal well
with multiple PICC's coming and going.
- Passive Sniffing of 14443
- dream: ethereal-like program for RFID
- h-field decreases tremendously with distance
- h-field antennas required
- reader -> picc signal strong and easily detected, beyon 10m
- picc -> reader signal very weak (60-70dB below reader->picc). so far
barely recognizable beyond 3m, even with 1m-loop-antenna
- various hardware approaches
- using software defined radio (gnuradio)
- quite expensive, unless you happen to already have one
- flexible, since everything can be done in software
- gnuradio-implementation of 14443 on my TODO list
- using dedicated demodulation hardware
- way cheaper than SDR
- 13.56MHz low enough for DIY-hardware
- under development by Milosch
- using existing reader ASIC, put it in read-only mode
- might be feasible, but operation is unlikely due to
lack of phase and clock synchronization with external
source
- ICAO compliant MRTDs
- ICAO already regulates MRZ on current travel documents in Doc 9303
- Working group created standards for new MRTD with biometric data
- Specifications publicly available
- 14443 A or B PICC
- ISO 7816-4 (inter-industry commands)
- LDS (Logical Data Structure)
- DG1
- data as printed on passport
- DG2
- facial JPEG, min 80pixels between eyes
- EF.SOD
- signature of DG1, DG2
- DG_FIXME
- optional fingerprint data
- Security
- passive auth
- basic access control
- prevents unauthorized reading by refusing
access until key derived from MRZ is
presented to PICC
- probably weak, since key is derived only from
DOB, document expiry date and document number
- provides session key generation for SM
encrypted transport layer
- active auth
- TR-PKI
- each country operates its own root CA
- intermediate document signer certificates
- country root certificates available via public LDAP
- certificates of all recognized countries need to be
stored in every inspection system
- certificate chain of EF.SOD signature can be verified
- specifies CRL polling intervals, etc.
- libicao
- aims to implement all required functions for access to ICAO MRTD
- basic access control present, but no secure messaging yet
- can use OpenCT or PC/SC as underlying API
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