OpenCard hack (projekt chameleon)

Cloning CryptographicRFID Cards for 25$November 29-30, WISSec 2010

Timo Kasper, Ingo von Maurich, David Oswald, Christof Paar

Department of Electrical Engineering and Information TechnologyChair for Embedded Security

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Cloning Cryptographic RFID Cards for 25$Timo Kasper, Ingo von Maurich, David Oswald, Christof Paar

Agenda

Motivation

RFID Basics

Mifare Classic

Mifare DESFire (EV1)

Real-World Attacks

Conclusion

Timo Kasper, WISSec 2010 | November 29-30, 2010

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Contactless Smartcards

use RFID (Radio Frequency Identification) technology

ISO 14443 A/B very popular: sufficient computational power for cryptography

large scale applications:

– Access control systems

– Electronic passports

– Payment systems

– Public transport ticketing


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Why Emulate Contactless Smartcards ? cards used or applications are often insecure

(e.g. no crypto / based on ID number only)

penetration-testing of real-world systems

emulating cards promises high profits for fraudsters estimate the real cost / risks

goals:

– card content and behavior freely programmable(e.g. arbitrary ID instead of fixed ID)

– assistance in analyzing unknown protocols

– support the relevant cryptographic primitivesTimo Kasper, WISSec 2010 | November 29-30, 2010

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Popular (ISO 14443) Contactless Smartcards

Mifare Classic

– Crypto1 stream cipher

– Very cheap, regarded completely broken

Mifare DESFire

– DES and 3DES

– More expensive, side-channel attacks possible

Mifare DESFire EV1

– AES-128 (and DES, 3DES)


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Agenda

Motivation

RFID BasicsMifare Classic


Chameleon

Real-World Attacks

Conclusion


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RFID Communication (ISO 14443)

• reader generates field with 13.56 MHz carrier frequency• supplies tag with clock and energy via inductive coupling• reader transmits data by short pauses in the field

(pulsed Miller code)• tag answers employing load modulation

(Manchester code)• operating range: 8…15 cm, data rate 106…847 kBit/s

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Mifare Classic


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• over 1 billion cards and 7 million readers sold

• authentication / data encryption with CRYPTO1 stream cipher

• each card contains a read-only Unique Identifier (UID) (4 byte)

• each sector can be secured: two cryptographic keys A and B

Mifare Classic (1K / 4K)

UID

Key A, sector 0 Key B, sector 0

Key A, sector 15 Key B, sector 15

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Mifare Classic Authentication Protocol

2. Challenge (Card → Reader)

1. Authentication request 3. Encrypted challenge (Reader → Card) || answer

4. Encrypted answer

1.

2.

3.

4.


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Security of Mifare Classic

… by obscurity

cipher and PRNG reverse-engineered in 2007

many attack vectors (weak PRNG, mathematical weaknesses in LFSR, parity bit attack)

card-only attacks: reveal all secret keys and memory content in minutes

Considered completely broken


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Mifare DESFire / Mifare DESFire EV1


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Mifare DESFire / Mifare DESFire EV1

7-byte read-only UID

communication can be secured by

– appended message authentication code (MAC)

– full data encryption

DES, 3DES and AES-128 (EV1) encryption! Side-channel attacks !


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Mifare DESFire Authentication Protocol

mutual authentication protocol, previously published

cards only perform (3)DES encryptions EncK(∙)

readers only perform (3)DES decryptions DecK(∙)


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Mifare DESFire Authentication Protocol

1. 1. Authentication request

2. 2. Encrypted nonce

3.3. Encrypted rotated

answer and nonce

5.5. Encrypted rotated answer

4. 4. Verify answer

6. 6. Verify Answer


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Mifare DESFire EV1 Authentication Protocol

reverse-engineered from genuine communications

similar to DESFire

differences:

– nonces are extended to 128 bit

– AES en-/decryptions are used in common sense

– CBC-mode chains all en-/decryptions even though they operate on different cryptograms

– second rotation is in the opposite direction


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Mifare DESFire EV1 Authentication Protocol

1. 1. Extended nonces

2.2. En-/Decryption is used in

common sense / Chained CBC (nR XOR b0)

3. 3. Rotation is changed to the opposite direction


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Agenda

Motivation

RFID Basics

Mifare Classic


Real-World Attacks

Conclusion


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Introducing:

Emulate contactless smartcards (ISO 14443)

Freely programmable, low-cost (less than $25)

Small, operates autonomously without a PC

EEPROM store bit streams for offline analysis


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– Operating Principle

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– Operating Principle

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– the Reality…

Antenna on PCBAnalog Circuitry( approx. 5€ )ATxmega (5€)

FTDI USB (4€)


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Hardware

off-the-shelf components

Atmel ATxmega192A3 8-Bit microcontroller

– 192kB Flash, 16kB SRAM, 4kB EEPROM

– Clocked at 27.12MHz (2 x 13.56 MHz)

– DES and AES-128 hardware accelerators

FTDI FT245RL enables USB communication

powered via USB or battery

card-sized antenna (fits into slots of most readers)


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Software (so far…)

full emulation of Mifare Classic cards

– UID can be freely chosen

– memory content and keys can be set arbitrarily

authentication mechanisms of Mifare DESFire & EV1

– UID can be freely chosen

– secret keys can be set arbitrarily


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Difficulties

strict timing requirements of ISO 14443:

– bit grid depending on the last bit sent by reader

– answer max. 4.8ms after request of the reader

Crypto1 is computationally intensive on µC:

– using an open C-library for Crypto1 results in inefficient code for 8-bit microcontrollers


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Straightforward CRYPTO1 Implementation

• platform: 8-Bit microcontroller, ATMega32

• clock frequency: 13.56 MHz

• encrypting one block (18 bytes) takes > 11 ms

too slow

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Crypto1 Optimizations

crypto1 implementation from scratch in assembly

replace filter functions with look-up tables

– size: 112 byte, negligible compared to 192kB Flash

random value for nC is generated before authentication

– aR and aC can be precomputed

– precomputing key stream bits not possible: sector key and reader nonce unknown a priori


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DESFire / DESFire EV1 Implementations

Straightforward on ATxmega

– 3DES in CBC mode

– AES-128 in “chained” CBC mode

3DES: three times faster than original card

– 219µs vs. 690µs for calculation of b3

AES-128: five times faster than original card

– 438µs vs. 2.2ms for calculation of b3Timo Kasper, WISSec 2010 | November 29-30, 2010

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Agenda

Motivation

RFID Basics

Mifare Classic


Real-World Attacks Conclusion


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Case Study: ID Card Contactless Payment System

• contactless employee ID card, more than 1 million users

• payments (max. 150 €), access control, …

• Mifare Classic 1K chip stores card number & credit amount

• ID cards have identical secret keys.

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Attacking a Contactless Payment System

Step 1: read out s.o. else’s (or your own…) card

Step 2: emulates an exact cloneincluding the UID → Fraud not detected

Credit gone? Step 3: Press state restoration button to restore the previous credit from EEPROM, goto Step 2

new operating mode: generate a random credit balance and new card number on each payment

cannot be blacklisted and blocked in the back-endTimo Kasper, WISSec 2010 | November 29-30, 2010

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Case Study 2: Widespread Access Control System

Mifare Classic 1K cards unlock doors and elevators

secret keys are default (0xA0A1A2A3A4A5)

penetration-test with

– identification by UID and 1st block of 1st sector

– access permissions checked in the back-end

1. read UID from authorized card2. set this UID in

OPEN SESAME!Timo Kasper, WISSec 2010 | November 29-30, 2010

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Access Control System in Idle Mode


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Clone on a Blank Card Fails


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Succeeds


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Agenda

Motivation

RFID Basics

Mifare Classic


Real-World Attacks

Conclusion


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Conclusion

cost-efficient ( < 25 $) freely programmable emulator for contactless smartcards

optimized Crypto1 implementation: Full Mifare Classic emulation successful in various real-world systems

(3)DES, AES support tested with emulation of MifareDESFire (incl. EV1) authentication

valuable tool for penetration-testing of RFID systems

cost for attacks often overestimated


Thanks!

Any questions?

Chair for Embedded Security (EMSEC)

Department of Electrical Engineering and Information Technology

{timo.kasper, ingo.vonmaurich, david.oswald, christof.paar}@rub.de

OpenCard hack (projekt chameleon)

Business

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answer timo kasper

david oswald

brokentimo kasper

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encrypted answertimo

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