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Physical Security. Overview. Smart cards RFIDs Attacks (Semi)-Natural tags Conclusions. Smart Cards. Smart cards. Broken!. 53.98 mm. 85.6 mm. 0.76 mm.

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Physical security

Physical Security


  • Smart cards

  • RFIDs

  • Attacks

  • (Semi)-Natural tags

  • Conclusions


Smart cards1
Smart cards


53.98 mm

85.6 mm

0.76 mm

[And96] R. J. Anderson and M. G. Kuhn. Tamper resistance - A cautionary note. In 2nd Int. Usenix Workshop on Electronic Commerce, pages 1-11, Oakland, California, Nov 1996. USENIX Association.


What makes the card smart
What makes the card smart?

  • CPU (8, 16, 32 bit)

  • Memory (RAM, ROM, EEPROM, Flash)

  • I/O channel (Contact/Contact less)

  • Cryptographic co-processor

  • On card devices (Fingerprint, display)

  • Standards (ISO 7816, GSM, EMV, VOP)


Main security features
Main security features

  • Symmetric crypto

  • Asymmetric crypto relatively slow

  • Hardware random number generator

  • Hardware tamper resistance

  • X-tal clock vulnerable

  • Life cycle management



  • ISO 7816-4:

    9600 bps : slow

  • USB : bulky

  • Bluetooth: power

  • Biometrics: slow



  • Plastic, glass

  • Emissive, non-emissive

  • Refresh, bi-stable

  • Segment, dot-matrix

  • Problems: connections, yield, power, thickness, price!

[Pra01] D. Praca and C. Barral. From smart cards to smart objects: the road to new smart technologies. Computer Networks, 36(4):381-389, Jul 2001.


Clock power
Clock & Power

  • Clock

    • Xtal 0.6 mm

    • MEMS (0.002% acc.)

  • Battery

    • Thickness

    • power density

    • when to recharge


Integration is hard
Integration is hard

  • Display

  • Button

  • 32-bit CPU

  • Large memory

  • Battery

  • Comms

  • >> 25mm2

Photo: Philips Semiconductors


What is an rfid tag
What is an RFID tag?

  • Antenna + small chip in ambient field

  • Passive, replies to queries only

  • Can be used for almost anything

    • Supply Chain Management & Checkout (Wallmart, Benetton)

    • Homeland security

    • User convenience

    • Access to buildings

Nokia 6131 NFC


Privacy issues
Privacy issues

  • Sniffing

    • Data collection in proximity (skimming)

    • Correlate data from different tags

  • Counter measures

    • Shield antenna in passport with tinfoil

    • Encrypt the template with MRZ data

    • Reduce transmit range

    • Light controlled on/off switch

    • Long and short range interface

    • Time delayed transmit of sensitive info

Watch this video

[Bir07] N. Bird, C. Conrado, J. Guajardo, S. Maubach, G. Jan Schrijen, B. Skorić, A. M. H. Tombeur, P. Thueringer, and P. Tuyls. ALGSICS - combining physics and cryptography to enhance security and privacy in RFID systems. In F. Stajano, C. Meadows, S. Capkun, and T. Moore, editors, 4th European Workshop on Security and Privacy in Ad-hoc and Sensor Networks (ESAS), volume LNCS 4572, pages 187-202, Cambridge, UK, Jul 2007. Springer.




[Wit02] M. Witteman. Advances in smartcard security. Information Security Bulletin, pages 11-22, Jul 2002.


  • Operational

    • Blackmail

    • Burglary

    • Bribery

  • Technical

    • Logical

    • Physical

    • Side channel

  • Attackers

    • I: Clever outsiders

    • II: Knowledgeable insiders

    • III: Funded Organisations


Logical attacks
Logical attacks

  • The code is too complex

    • Hidden commands

    • Parameter poisoning & Buffer overflow

    • Malicious or buggy applets

    • Protocol problems (e.g. retransmit)

    • Proprietary crypto

  • Counter measures

    • Structured design & code inspection

    • Formal methods

    • Testing


Example rfid virus
Example: RFID virus

  • There is a large amount of code

  • Generic protocols and facilities

  • Back end data bases

  • So the usual attacks:

    • Buffer overflow

    • SQL injection “;shutdown--”

  • Don’t trust data from RFID tag…

Best paper


[Rie06] M. R. Rieback, B. Crispo, and A. S. Tanenbaum. Is your cat infected with a computer virus? In 4th Annual IEEE Int. Conf. on Pervasive Computing and Communications (PerCom), pages 169-179, Pisa, Italy, Mar 2006. IEEE Computer Society.


Physical attacks
Physical attacks

  • The circuitry is complex and vulnerable

    • Chemicals & etching

    • SEM Voltage contrast

    • Probe stations

    • Focused Ion Beam (FIB) to make probe pads

  • Counter measures

    • Reduced feature size (100nm)

    • Multi layering

    • Protective layers

    • Sensors

    • Bus scrambling


Low cost physical attacks
Low cost physical attacks

  • Block EEPROM writes by isolating Vpp

  • Rent focused Ion beam

[And97d] R. J. Anderson and M. Kuhn. Low cost attacks on tamper resistant devices. In 5th Int. Workshop on Security Protocols, volume LNCS 1361, pages 125-136, Paris, France, Apr 1997.


Side channel attacks
Side channel attacks

  • Physical phenomena can be measured

    • Power

    • EM radiation (X-ray, light, sound)

    • Time

  • and changed

    • Voltage (example later)

    • Frequency (example later)

Watch this video

[Vua09] M. Vuagnoux and S. Pasini. Compromising electromagnetic emanations of wired andWireless keyboards. In 18th USENIX Security Symp., pages 1-16, Montreal, Canada, Aug 2009. USENIX Assoc.


Timing attack
Timing attack

  • Exponentiation by square and multiply

    • for i = n − 2 downto 0

    • X = X2

    • if (d[i] == 1) then

    • X = X*M

  • Power trace shows bits 1 in the key


Simple power analysis
Simple power analysis

  • 16 rounds DES

  • Rounds 2 & 3

[Koc99] P. C. Kocher, J. Jaffe, and B. Jun. Differential power analysis. In M. J. Wiener, editor, 19th Int. Conf. on Advances in Cryptology (CRYPTO), volume 1666 of LNCS, pages 388-397, Santa Barbara, California, Aug 1999. Springer.


Differential power attacks
Differential power attacks

  • Difference in the third cycle due to difference in input value for encryption


Active attacks power dip
Active attacks : Power Dip

A power Dip at the

Moment of reading

a memory cell


  • read a 0 as a 1

  • Protection measure

    • Check VCC & raise an alarm if it drops

    • Problem: Fast transients during start-up may raise false alarms



Stored value

of logical zero



Active attacks clock glitch
Active attacks : Clock Glitch

  • Dump all of the memory

  • Replace 5MHz pulse by 4 pulses of 20MHz:

    • b = answer_address

    • a = answer_length

    • If (a == 0) goto 8

    • transmit(*b)

    • b=b+1

    • a=a-1

    • goto 3

Glitch here

[And97d] R. J. Anderson and M. Kuhn. Low cost attacks on tamper resistant devices. In 5th Int. Workshop on Security Protocols, volume LNCS 1361, pages 125-136, Paris, France, Apr 1997.



  • Hardware

    • Lower power signals

    • Increase noise levels

    • Introduce timing noise

  • Software

    • Parallelism

    • Introduce random delays

    • Constant time execution

    • Blinding intermediate values



  • Make attacks harder but not impossible

  • Hard to get right

  • Expensive to implement


Out of the box thinking
Out of the box thinking

  • The humble Capacitor

    • Emanates acoustic signals

    • Sensitive to shocks and vibration

    • C  A / d


Listen to a pc multiplying
Listen to a PC multiplying

Freeze 1500 μF



Design guidelines
Design guidelines

  • Define the level of security needed

  • Perform a risk analysis

  • Consider the attackers business case

  • Use the right technologies

  • Build in fraud management

  • Design recovery and fall-back

  • Consider the overall system


Ibm 4758 crypto coprocessor
IBM 4758 Crypto Coprocessor

  • Rolls Royce of secure devices

  • Tamper sensing barrier

  • Keys move in the RAM

  • Temperature & X-ray sensor

  • Solid aluminium case & epoxy potting

  • low pass filter on power supply

  • Used in ATMs

  • Hacked!

[Cla03b] R. Clayton and M. Bond. Experience using a Low-Cost FPGA design to crack DES keys. In 4th Int. Workshop on Cryptographic Hardware and Embedded Systems (CHES), volume LNCS 2523, pages 877-883, Redwood Shores, California, 2003. Springer.


Finger printing
Finger printing

[Buc05] J. D. R. Buchanan, R. P. Cowburn, A.-V. Jausovec, D. Petit, P. Seem, G. Xiong, D. Atkinson, K. Fenton, D. A. Allwood, and M. T. Bryan. Forgery: 'fingerprinting' documents and packaging. Nature, 436(7050):475, Jul 2005.


Philips coating puf
Philips Coating PUF

[Sko08] B. Škorić, G.-J. Schrijen, W. Ophey, R. Wolters, N. Verhaegh, and J. van Geloven. Experimental hardware for coating PUFs and optical PUFs. In P. Tuyls, B. Škorić, and T. Kevenaar, editors, Security with Noisy Data - On Private Biometrics, Secure Key Storage and Anti-Counterfeiting, pages 255-268. Springer London, 2008.


Mems particles
MEMS particles

  • 1x1x12 m particles, shapes

  • Church and school roof, power line grease/gel

  • Jewellery fluid

  • Spray vandals/thiefs

  • Smart water

Watch this video

[Kay92] P. H. Kaye, F. Micheli, M. Tracey, E. Hirst, and A. M. Gundlach. The production of precision silicon micromachined non-spherical particles for aerosol studies. Journal of Aerosol Science, 23(Suppl 1):201-204, 1992.



  • Affordable tamper resistance technology exists

  • Getting it right is difficult

  • Out of the box thinking required