Nanofocused X-Ray Beam To Reprogram Secure Circuits

Transcription

1 Nanofocused X-Ray Beam To Reprogram Secure Circuits Stéphanie Anceau, Pierre Bleuet, Jessy Clédière, Laurent Maingault, Jean-luc Rainard, Rémi Tucoulou

2 Let s speak about X-rays Ionizing radiations are often mentioned in literature, but without real practical results Lots of references in failure analysis and space systems literature A new method of perturbation? We propose using a nanofocused X-ray beam of a synchrotron 2

3 How did we get to a synchrotron? after doing some preliminary tests on more simple equipment medical equipment material science equipment 3

4 With some basic focusing a hole in a lead sheet X-ray exposed area lead die Device Under Test PCB ZIF support 4

5 ATMEGA A fairly old circuit (350 nm) but useful to investigate new attacks 5

6 ATMEGA layout E E P R O M flash RAM logic 500 µm 6

7 ATMEGA + lead sheet and hole we fill flash memory with value 0x55 7

8 First faults obtained after 210 seconds of exposure red: 1 to 0 corruption 8

9 40 seconds later 9

10 then 40 more 10

11 and finally 11

12 What happened? floating gate transistor access transistor 12

13 Data is stored in the floating gates charge in the floating gate: transistor is blocked value 1 is stored no charge in the floating gate: transistor is conductive value 0 is stored 13

14 Access to the floating gates access transistors of the active line are conductive 14

15 X-ray exposure : we discharge the floating gates 15

16 Access to the data 16

17 X-ray exposure continued : we semi-permanently switch on access transistors 17

18 Column errors 18

19 Column errors 19

20 Two major effects observed during these first tests We empty floating gates of carriers we could modify (1 to 0) flash and EEPROM We modify transistors semi-permanently NMOS are made conductive (and PMOS blocked) it is reversible with a heat treatment (150 C, 1 hour) The last result applied to logic area of the circuit : we could reconfigure circuits : circuit edit 20

21 Two major effects observed during these first tests (cont d) These effects are described in the space systems literature and are very interesting for our activity let s focus X-rays down to the nano-scale to target a single transistor! 21

22 Grenoble, France Léti ITSEF European Synchrotron Radiation Facility (ESRF) 500 m 22

23 Inside the donut 23

24 Focusing to the nano scale: 60 nm X-ray spot long focal length optic fluorescence detector X-ray X-ray ATMEGA at the focal point of X-ray optic 24

25 Fluorescence image by scanning the IC with the nano-beam tungsten fluorescence mapping cross-section (SEM view) tungsten via SEM view 25

26 Obtained results on ATMEGA Fluorescence mapping allows powerful and accurate positioning at the transistor level Flash and EEPROM can be modified (1 to 0) at the bit level : code of a circuit can be changed (good example in the proceedings) Single RAM cells can be semi-permanently stuck at 0 or 1 by corrupting transistors Logic can be modified at the transistor level : circuit edit this could be used to: change the behavior of the circuit remove hardware countermeasures No need to open the package of the die 26

27 RAM results on ATMEGA SEM view fluorescence view superposition and results RAM address RAM cell stuck at 0 RAM cell stuck at 1 5 µm 27

28 Obtained results on state of the art technology node Fluorescence mapping still allows a powerful and accurate positioning at the transistor level Flash / EEPROM can still be modified (1 to 0) at the bit level (110 nm and 90 nm NOR flash) Single RAM cells can still be stuck at 0 or 1 (45 nm microcontroller) Still no need to open the package of the die 28

29 Comparison Nanofocused X-rays could be compared to laser perturbation or to Focused Ion Beam (invasive attack, circuit edit) Implementation is like a laser setup with no sample preparation required (package opening, thinning ). But very small spot (60 nm or less): reverse engineering is required! Effects are like invasive attacks but totally non invasive! FIB: modification of metal layers of the circuit X-rays: modification of the transistors of the circuit 29

30 The cost of such a thing? Cost of a FIB access via service : 400 / hour Cost of ESRF access via industrial channel : 3000 for 8 hours 30

31 Conclusion on nanofocused X-ray A new technique to attack circuits and to perform circuit-editing Extreme resolution with accurate positioning thanks to the use of fluorescence mapping Tool with a difficult access, but not that expensive! Experiments are still ongoing. 31

32 Thanks Leti, technology research institute Commissariat à l énergie atomique et aux énergies alternatives Minatec Campus 17 rue des Martyrs Grenoble Cedex France