From b4915a6f814e1b410063c1da83057af232346af0 Mon Sep 17 00:00:00 2001
From: Harald Welte <laforge@gnumonks.org>
Date: Fri, 13 Aug 2010 14:50:58 +0800
Subject: import easycard paper

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+\documentclass[a4paper]{article}
+\usepackage[english]{babel}
+\usepackage{graphicx}
+\usepackage{subfigure}
+\pagestyle{plain}
+
+%\usepackage{url}
+
+\setlength{\oddsidemargin}{0in}
+\setlength{\evensidemargin}{0in}
+\setlength{\topmargin}{0in}
+\setlength{\headheight}{0in}
+\setlength{\headsep}{0in}
+\setlength{\textwidth}{6.5in}
+\setlength{\textheight}{9.5in}
+%\setlength{\parindent}{0in}
+\setlength{\parskip}{0.05in}
+
+\begin{document}
+
+\title{Security analysis of the EasyCard payment card in Taiwan}
+\author{Harald Welte $<$laforge@gnumonks.org$>$}
+\date{August 31, 2010}
+\maketitle
+
+\begin{abstract}
+The EasyCard system, established in 2001, is the most popular store-valued card
+in Taiwan.  With more than 18 million issued cards, it is the predominant means
+of paying for public transportation services in the capital Taipei.
+
+In 2010, use of the EasyCard was extended beyond transportation.  Card holders
+can now pay in all major convenience stores and major retail companies like
+Starbucks or even SOGO.
+
+However, the system is still using the MIFARE Classic RFID transponder
+technology, whose very limited security-by-obscurity proprietary encryption
+system (CRYPTO1) has been broken years ago.
+
+This document analyzes the results of combining the practical attacks
+on the MIFARE Classic CRYPTO1 system in the context of the EasyCard payment
+system.
+\end{abstract}
+
+\tableofcontents
+
+\section{Foreword}
+
+This document is the result of my personal research on the EasyCard
+system.  It was done out of my personal interest in security research
+on information technology.  No competitor of the EasyCard corporation,
+or other business or political  stakeholder ever encouraged, supported or
+funded this work in any way.
+
+The result of this research is presented to the general public in the
+hope it will make people re-consider the amount of trust they place
+in proprietary systems that provide no evidence of their security,
+and no option for the general public or the scientific community to
+validate it.
+
+This paper is also directed at the legislator and the regulatory authorities,
+in the hope that it will help them to produce better rules and requirements on
+the technology designed for and usedby  operators of security relevant systems
+such as banking.
+
+\section{Introducing the EasyCard}
+
+FIXME
+
+\section{Published security research on MIFARE Classic}
+
+FIXME
+
+\section{Published tools for MIFARE Classic attacks}
+
+FIXME
+
+\section{Analyzing the EasyCard}
+
+A new, genuine EasyCard was obtained from one of the EasyCard vending machines
+in a Taipei MRT station.
+
+As it is public knowledge that the EasyCard system is based on MIFARE
+technology, any MIFARE-compatible RFID reader (PCD, Proximity Coupling Device)
+can be used to establish a physical communications link according to ISO
+14443-1 and -2, as well as performing the anti-collision procedure according
+to ISO 14443-3.
+
+The author has used the OpenPCD RFID reader to do this, and has confirmed that
+the EasyCard in fact is a card with ISO 14443-3 compatible anti-collision
+procedure.  The ATQA response also looks like that of a standard MIFARE Classic
+transponder.
+
+\subsection{Attempting to use standard keys}
+
+As some users of MIFARE Classic systems only use some sectors of a card, but
+not all, an attempt was made to authenticate to any of the blocks using the
+manufacturer-programmed standard keys.  However, none of the card sectors were
+using those standard keys.
+
+This also means that we could not use the key recovery method described in
+FIXME, where keys of all other sectors are recovered based on the knowledge of
+they key of at least one different sector.
+
+\subsection{Recovering the MIFARE CRYPTO1 keys}
+
+Since none of the sector keys was known, the publicly available MFCUK (MiFare
+Classic Universal toolKit) implementation of the "Dark Side" attack (Nicolas T.
+Courtois) was used as a card-only attack.
+
+All that was required was the MFCUK Free Software, as well as a RFID
+reader as supported by libnfc.  Compatible readers are widely available,
+among them one for EUR 30 from http://www.touchatag.com/e-store.
+
+Using the MFCUK key recovery tool, the A and B keys for all sectors have
+been recovered within FIXME.  This attack can definitely be optimized
+by using special-purpose hardware such as the Proxmark, which gives
+hard-realtime control over the communication with the EasyCard.
+
+Furthermore, the key recovery can be optimized based on known-plaintext that is
+common to all cards.
+
+\subsection{Dumping the content of the EasyCard}
+
+Once the sector keys have all been recovered, the full content of the EasyCard
+can be dumped using any RFID reader supporting MIFARE Classic.  The author
+chose to use the same reader that was used for the MFCUK key recovery combined
+with the nfc-mfclassic program (part of libnfc).
+
+A full dump of the newly-purchased, unused EasyCard revealed the following
+content:
+
+0000000 a193 c031 88c3 0004 ba46 1214 1051 1004
+0000010 140e 0100 0207 0308 0409 1008 0000 0000
+0000020 0000 0000 0000 0000 0000 0000 0000 0000
+0000030 211a ccd0 f399 7708 008f 6ac6 53bf cf08
+0000040 ff02 0300 0000 059f 804c c926 0171 3601
+0000050 0000 1000 1027 0027 64de 0001 0000 bb00
+0000060 f1d6 b4e8 0012 0000 0000 6400 0064 6900
+0000070 2e64 f724 bd57 7708 008f 8917 3d48 5dcd
+0000080 0190 0000 fe6f ffff 0190 0000 ff00 ff00
+0000090 0190 0000 fe6f ffff 0190 0000 ff00 ff00
+00000a0 0000 0000 0000 0000 0000 0000 0000 0000
+00000b0 0d3d 782b 33cd 7708 008f 2411 4ce7 ea3f
+00000c0 0001 0005 0000 0000 0000 0000 0000 0000
+00000d0 0000 0000 0000 0000 0000 0000 0000 0000
+00000e0 0000 0000 0000 0000 0000 0000 0000 0000
+00000f0 2fb1 511f 85b4 7708 008f 8dc8 eef5 2850
+0000100 0000 0000 0000 0000 0000 0000 0000 0000
+0000110 0000 0000 0000 0000 0000 0000 0000 0000
+0000120 0000 0000 0000 0000 0000 0000 0000 0000
+0000130 4587 96bd 1f22 7708 008f 47ce 7619 1558
+0000140 0000 0000 0000 0000 0000 0000 0000 0000
+0000150 0000 0000 0000 0000 0000 0000 0000 0000
+0000160 0000 0000 0000 0000 0000 0000 0000 0000
+0000170 5583 7616 749e 7708 008f 9bf3 c129 8eb6
+0000180 0c00 0400 0044 0000 0000 0000 0000 4c00
+0000190 0200 2200 0022 0000 0000 0000 0200 0000
+00001a0 0000 0005 0000 0000 0000 0000 0000 0000
+00001b0 af5f 6aeb 3a2c 7708 008f c039 7a1d d248
+00001c0 0000 0000 0000 0000 0000 0000 0000 0000
+00001d0 0000 0000 0000 0000 0000 0000 0000 0000
+00001e0 0000 0000 0000 0000 0000 0000 0000 0000
+00001f0 aebf 906e f2bd 7708 008f e3e7 988f aaaa
+0000200 0000 0000 0000 0000 0000 0000 0000 0000
+0000210 0000 0000 0000 0000 0000 0000 0000 0000
+0000220 0000 0000 0000 0000 0000 0000 0000 0000
+0000230 ec9f 8bc6 4b89 7708 008f 53b0 2571 9e66
+0000240 0000 0000 0000 0000 0000 0000 0000 0000
+0000250 0000 0000 0000 0000 0000 0000 0000 0000
+0000260 0000 0000 0000 0000 0000 0000 0000 0000
+0000270 edc5 c17c 8a36 7708 008f 9a58 b6d9 5a8b
+0000280 0000 0000 0000 0000 0000 0000 0000 0000
+0000290 0000 0000 0000 0000 0000 0000 0000 0000
+00002a0 0000 0000 0000 0000 0000 0000 0000 0000
+00002b0 40f7 60bf 4b8a 7708 008f 3a00 c93a 63e8
+00002c0 0000 0000 0000 0000 0000 0000 0000 0000
+00002d0 0000 0000 0000 0000 0000 0000 0000 0000
+00002e0 0000 0000 0000 0000 0000 0000 0000 0000
+00002f0 b50a 9f96 d2e3 7708 008f 4855 7cdb 7dff
+0000300 0000 0000 0000 0000 0000 0000 0000 0000
+0000310 0000 0000 0000 0000 0000 0000 0000 0000
+0000320 0000 0000 0000 0000 0000 0000 0000 0000
+0000330 4c06 3ebc e595 7708 008f 9a5b 001b d14a
+0000340 0000 0000 0000 0000 0000 0000 0000 0000
+0000350 0000 0000 0000 0000 0000 0000 0000 0000
+0000360 0000 0000 0000 0000 0000 0000 0000 0000
+0000370 3fb0 45ce 6f6b 7708 008f c0bf adb0 d662
+0000380 0000 0000 0000 0000 0000 0000 0000 0000
+0000390 0000 0000 0000 0000 0000 0000 0000 0000
+00003a0 0000 0000 0000 0000 0000 0000 0000 0000
+00003b0 3320 9074 e84c 7708 008f 0094 85d5 7aaa
+00003c0 8000 c926 0071 0000 0000 0000 0064 0064
+00003d0 0000 0000 0000 0000 0000 0000 0000 0000
+00003e0 0000 0000 0000 0000 0000 0000 0000 0000
+00003f0 ea02 0bda b62a 7708 008f 0000 0000 0000
+
+\subsection{Re-engineering the on-card data format}
+
+When the author started his research, there was no pre-existing public
+knowledge on the data format used by the EasyCard system.  As such,
+significant time was spent analyzing it.
+
+The card was subsequently used to perform a number of transactions such as
+use of public transportation and purchase of goods in stores.
+
+After each transaction, again a full dump of the card contents was made,
+and the difference to the previous dump analyzed carefully.  No particular
+tools have been used for analysis.  Most of the work relied on hex-dumps
+of the card content and using the {\tt diff} utility to visualize differences
+between two consecutive versions.
+
+During the analysis, it was quickly revealed that there are four
+distinctive sets of changes that can be associated with a transaction:
+\begin{itemize}
+\item The card balance, stored as MIFARE value block
+\item The transaction log
+\item The transaction log index
+\item The last MRT entry/exit record
+\end{itemize}
+
+Furthermore, a constant header has been identified. It was never changed during
+any of the tested transactions.
+
+The result of this analysis can be found in the next section:
+
+\section{Re-engineered EasyCard Data Format}
+
+\subsubsection{Sector 0 and 1: The header}
+\subsubsection{Sector 2: The card balance as value block}
+
+The first two blocks of Sector 3 store the current remaining debit account
+balance as a MIFARE Classic VALUE BLOCK.  The format of this block is
+documented in the official NXP vendor documentation on the MIFARE chip
+used inside the card.
+
+The value block is decremented every time payment is made with the card.
+
+Given the MIFARE access bits, it is assumed that the RFID readers in public
+transportation as well as stores use key A for this sector, as key A is
+sufficient to read and decrement the VALUE block.
+
+Re-charging the card must happen using authentication with key B, as only
+Key B has permissions to increment and/or write to this sector.
+
+\subsubsection{Sectors 3 through 5: The transaction log}
+
+Every time a transaction is made with the card, an entry in the transaction log 
+on the card itself is generated.  Every entry occupies one full 16-byte block.
+
+The structure of a transaction log entry is as follows:
+\begin{itemize}
+\item 1 byte Transaction ID
+\item 4 bytes Timestamp
+\item 1 byte Transaction type
+\item 2 bytes Cost charged for transaction
+\item 2 bytes Remaining balance after transaction
+\item 1 byte MRT Station ID
+\item 1 byte Unknown
+\item 2 bytes RFID Reader ID
+\item 2 bytes Unknown
+\end{itemize}
+
+The {\em Transaction ID} is a monotonically increasing value, incrementing with
+each transaction.
+
+The {\em Timestamp} is a 32bit value in the standard UNIX time() format (Seconds
+since January 1st 1970 00:00:00).  However, it does not reference UTC but CST.
+
+The {\em Transaction type} indicates the type of transaction.  Following codes
+are known:
+\begin{itemize}
+\item {\tt 0x00} Entering MRT station
+\item {\tt 0x11} Leaving MRT station
+\item {\tt 0x80} Re-entering (connecting) MRT station
+\item {\tt 0x20} Purchase of goods in shop
+\end{itemize}
+
+The {\em Cost} and {\em Remaining balance} fields are unsigned 16bit integer
+values representing the price in NTD (New Taiwan Dollars).
+
+In case of a MRT related transaction, the {\em MRT Station ID} encodes the MRT
+station at which the transaction was performed.  By visiting the TRTC (Taiwan
+Rapid Transport Corporation) website, one can see the same numeric identifiers
+being used within the URLs that link from the MRT map to the per-station web
+pages.  As such, a full table of MRT station names and corresponding
+identifiers has been compiled and implemented as part of {\tt easytool}.
+
+The {\em RFID Reader ID} is presumed to be a unique identifer for the specific
+RFID Terminal.  Subsequent transactions at the same terminal will render
+the same number in this field.
+
+\subsubsection{The transaction log pointer}
+
+\subsubsection{Sector 7: The last MRT entry/exit record}
+
+Block 2 (Offset 0x1e0) contains a record dscribing the last MRT station
+that was entered using this EasyCard.
+\begin{itemize}
+\item Bytes 0...3 are unknown
+\item Byte 4 contains the MRT station code
+\item Bytes 6...8 are unknown
+\item Bytes 9...12 contain the Timestamp
+\item Bytes 13..15 are unknown
+\end{itemize}
+
+Block 1 (Offset 0xd0) of the same sector contains a record using the same
+structure.  However, this record describes the last MRT station that was
+left using this EasyCard.
+
+It is assumed that this information is used by the system to compute both the
+distance (and thus fee) to be paid by the current ride, as well as any
+applicable discount in case a connection is made from MRT into a bus.
+
+\section{Manipulating the EasyCard}
+
+\section{Mistakes of the EasyCard Corporation}
+
+\subsection{Deploying old technology}
+
+The Taipei Smart Card corporation (predecessor to the EasyCard Company) was
+established in 2000, and it took until June 2002 to deploy the first EasyCard
+system.
+
+The underlying Mifare Classic product was launched in 1994, and thus already
+relatively old and outdated technology at that time.
+
+It was publicly documented by NXP that the security of the system is baesd on a
+{\em prorprietary, symmetric, 48bit cipher}.  Symmetric 48-bit encryption
+was definitely no longer state-of-the-art in the year 2000.  At that time,
+the popular web-browser Netscape Navigator (used e.g. for web-based online
+banking) had already introduced support for symmetric 128bit ciphers.
+
+\subsection{Deploying proprietary security technology}
+
+There are two concepts of achieving security in any system: {\em Security by
+design} and {\em Security by obscurity}.
+
+In the former systems, security is achieved by using well-designed systems
+that have undergone public peer review and have been subject to cryptanalysis.
+As a result, the system is secure because it has undergond the review and
+scrutiny of the international community of cryptographers and security experts.
+
+So, despite making all details of the system, particularly the cryptographic
+algorithms open, an attacker is not able to circumvent the systems security.
+
+A system relying on {\em Security by obscurity} is only secure because
+nobody knows the details of how it works.  As soon as this information
+has either leaked or recovered e.g. using reverse engineering techniques,
+the system is broken.
+
+FIXME: Link to Bruce Schneier
+
+\subsection{Not reacting to academic research in the field}
+
+Starting in 2007, researchers have published a variety of attacks on
+the CRYPTO-1 cipher and MIFARE Classic system.  For a list of related
+publications, see the bibliography of this paper.
+
+\subsection{Not reacting to public availability of MIFARE attack tools}
+
+Following-up the scientific publications, tools implementing practical
+attacks on MIFARE Classic have been developed and published.  Such
+tools implement a variety of attacks, including card-only key-recovery
+attacks.
+
+\subsection{No upgrade to more secure cards as they become available}
+
+In the same year the EasyCard was first deployed (2002), the supplier of the
+MIFARE Classic system has already been shipping a much more secure system
+called DESfire.  The improvements include: 112-bit key length, and the use
+of the internationally verified and audited DES algorithm in its 3DES variant.
+
+Despite its availability for 8 years since 2002, the EasyCard corporation has
+apparently never updated their system to a more secure card like the DESfire
+card.
+
+Based on the authors experience with the RFID card market, the price difference
+of DESfire compared to MIFARE Classic has been on the order of USD 1 per card
+from 2006 on.
+
+So, in order to save USD 1 per each issued card, the EasyCard corporation has
+artificially kept down the security level of their system,  not catching
+up with state-of-the-art commercially available technology.
+
+\subsection{Extending EasyCard to generic payment outside public transport}
+
+The security of any system always has to be analyzed in the context of the
+threat model, i.e. what can an attacker gain from compromising the system.
+
+As the key derivation of the EasyCard is not (yet?) broken, it is thus
+currently not possible to completely manufacture forged cards.  However,
+technically, cards can be re-charged without making actual payment for it.
+
+As far as cards are only used for public transportation, the incentive
+for fraudulent use is relatively small and contained.  Also, the amount
+of money for each transaction is realtively small.
+
+Thus, while the author would still disagree, it might be the case that
+the business risk analysis inside EasyCard Corporation would have deemed the
+risk of fraud in the public transport sector as acceptable.
+
+When such a card is used as an electronic payment system in stores where
+goods of much higher value can be purcased, the threat model is quite
+different, though.
+
+The 2010 introduction of the EasyCard as means of payment in retail
+stores - while still relying on known-broken, 16 year old technology -
+can thus only be seen as ignorant and incompetent.
+
+It does not help that EasyCard corporation has to provide a full refund
+and keep all deposits in a bank trust.  It also doesn't help that fraudulent
+use is detected using analysis of the transaction data long after it happened.
+
+EasyCard fraud is simple to perform and will inevitably happen.  Somebody
+has to pay for the losses incurred due to fraud.  Even if such losses
+only reflect themselves in increased transaction fees for retail stores, in the
+end it will be the consumer who pays them indirectly due to higher prices
+including such fees.
+
+\section{Proposed Changes / Improvements}
+
+The author of this paper argues that use of the current EasyCard system
+should immediately be restricted to payment for public transportation,
+and the decision to authorize it as form of payment in retail stores
+as of April 1st, 2010 reverted.
+
+A new system, based on state-of-the-art technology and algorithms
+and the {\em Security by Design} principle should be developed.  Such
+a system should go through independent, open academic review.
+
+The approval of such a system, or technical security requirements for
+such a system should not be within EasyCard itself, but should be
+made by a regulatory authority, consulted by independent technical experts
+in the field.
+
+A changing roll-over to the new system can be made by starting to issue
+the new cards using a more secure RFID system whenever new EasyCards are
+bought.  Whenever a consumer wants to re-charge their card, the old MIFARE
+Classic based card should be retracted and a new, more secure card be issued.
+Existing EasyCards can be circulated in the system for a grace period.
+
+Depending on the technical details of the existing deployed RFID
+reader/terminal base in public transportation and retail stores, either
+a software-only update is sufficient or replacement hardware has to be
+introduced.
+
+EasyCard corporation should be liable for the complete system
+upgrade/transition cost, as the fault of the system can only be blamed
+on them.
+
+\section{Bibliography}
+%1. [WPMCC09] - "Wirelessly Pickpocketing a Mifare Classic Card"
+%2. [ESO08] - "2008-esorics.pdf"
+%3. [ESOSL08] - "2008-esorics-slides-updated.pdf"
+%4. [KON08] - "2008-koning-thesis.pdf"
+%5. [VER08] - "2008-verdult-thesis.pdf"
+%6. [PATMC] - "A Practical Attack on the MIFARE Classic.pdf"
+%7. [NCOURFIDSEC09] - "mifare_courtois_rfidsec09.pdf"
+%8. [MFCLTRB09] - "MifareClassicTroubles.ppt"
+%9. [TEEP08] - "p2008-teepe-classic_mistakes.pdf"
+%10. [RFIDSANJ] - "RFID Attacks_WCA_San_Jose.pdf"
+%11. [ROSS] - "rossum-mifare.pdf"
+%12. [PLOTZ08] - "SAR-PR-2008-21_.pdf"
+%13. [ROSSSASG] - "SASG35_Peter_v_Rossum_Mifare.pdf"
+%14. [DARK2009] - "THE DARK SIDE OF SECURITY BY OBSCURITY and Cloning MiFare Classic Rail and Building Passes, Anywhere, Anytime"
+
+\end{document}
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