WO2018210954A1

WO2018210954A1 - Device for protecting an electronic card

Info

Publication number: WO2018210954A1
Application number: PCT/EP2018/062789
Authority: WO
Inventors: Eric Richard; Pascal Commun; Anthony MARZELIERE
Original assignee: Thales
Priority date: 2017-05-16
Filing date: 2018-05-16
Publication date: 2018-11-22
Also published as: FR3066632A1; FR3066632B1

Abstract

The invention relates to a device (10) for protecting an electronic card, the protection device being able to be connected to said electronic card, and comprising: - a mesh for protecting at least one predetermined zone of the electronic card to be protected; and - an electronic measurement component (14), capable of being connected to the protection mesh, used as a sensor of at least one electrical quantity passing therethrough, the electronic measurement component (14) being configured to measure the inductance of the protective mesh; and, in the event of the detection of an inductance variation that is greater than a predetermined threshold, being configured to transmit or supply information representing said inductance variation to a module for processing and/or for transmitting data of the protection device.

Description

Device for protecting an electronic card

The present invention relates to the field of own electronic card protection to be used in many electronic devices, including sensitive electronics in terms of confidentiality and ^integrity.

More specifically, the invention relates to an electronic card protection device, the protection device being connectable to said electronic card.

The invention also relates to an electronic card to which said protective device is connected. To prevent the intrusion of malicious third parties into an electronic card capable of storing or processing sensitive data requiring security, a protective element in the form of a hood or a network of routed tracks of the circuit board of the electronic card is conventionally used. implemented.

Such a protection element or protection mesh aims to prevent access to data signals received or transmitted by the electronic card and / or prevent access to sensitive data transiting or stored on the electronic card.

To do this, such a protection element or protection mesh of the state of the art forms an electrically closed loop. The detection of a malicious intrusion is then binary and simply based on the resistive detection of the opening of the closed loop causing a detectable loop voltage level change.

However, it is easy for a malicious third party to bypass such protection by placing a resistor or a shunt-mounted track, also called a "shunt" on either side of the opening in the protective element so as to restore a closed loop even when an undetectable intrusion is made at the opening, the loop being closed by other elements of derivation.

One of the aims of the invention is therefore to propose a reinforced protection device compared to the state of the art, by making it possible in particular to detect bypass derivations, hitherto undetectable, while continuing to detect intrusions more by opening the electrically closed loop of the protection element.

To this end the invention relates to a device for protecting an electronic card, the protection device being connectable to said electronic card, and comprising: a protection mesh of at least one predetermined zone of the electronic card to be protected, and

an electronic measurement component capable of being connected to the protection mesh used as a sensor of at least one electrical quantity passing through it,

the electronic measurement component being configured to measure the inductance of the protection mesh, and, in case of detection of a variation of inductance greater than a predetermined threshold, configured to transmit, or to provide to a processing module and / or data transmission system of the protection device, an information representative of said variation of inductance.

Since a protective mesh is a particular track to be characterized in particular by its inductance, the protection device according to the invention is based on the presence of an electronic measurement component configured to continuously measure the inductance of the mesh of protection. Thus, any modification of the protection mesh by opening or by laying a shunt induces a modification of the inductance of the track which is detectable by the protection device according to the invention.

According to a particular embodiment, the protection device comprises one or more of the following characteristics, taken separately or in any technically possible combination:

the electronic measurement component is an inductance-to-digital converter;

the equivalent circuit of the protection mesh is an inductive circuit comprising at least a first coil representative of the equivalent inductance of the protective mesh;

the equivalent inductive circuit of the protection mesh further comprises at least a first resistance representative of the equivalent resistance of the protection mesh forming with said first coil representative of the equivalent inductance of the protection mesh a first circuit Rsi U series

the electronic measurement component is connected in parallel with a capacitor, the capacitor being connected in parallel, in at least one closed loop, to at least said protection mesh;

the closed loop further comprises a second coil and a second resistor forming a second series circuit R _S 2I-2, the capacitor being connected in parallel with the first circuit Rsi U equivalent series of the protection mesh, and in series with the second circuit R _S 2 series. the closed loop has an oscillation frequency belonging to a predetermined frequency range, and has a loop impedance belonging to a predetermined impedance value range, the oscillation frequency and the loop impedance both conditioning the resistor (s), coil (s) and capacitor values of the electronic components of the closed loop.

the protective mesh has a pattern belonging to the group comprising at least:

- a serpentine pattern;

- a pattern in the form of boustrophedon;

a square-shaped pattern capable of framing the predetermined zone of the electronic card to be protected;

- a snail-shaped pattern;

- a spiral pattern;

- a randomly generated pattern;

the protective mesh is capable of comprising at least one monolayer part and / or at least one multilayer part superimposed on a ground plane;

when the protective mesh comprises at least one multilayer part, the protection mesh of said part is able to present a different pattern from one layer to another and / or a pattern rotation and / or a pattern offset of one layer to another

the protection device comprises a microcontroller configured to drive the inductance-to-digital converter.

The invention also relates to an electronic card to which said protective device is connected.

Other features and advantages of the invention will emerge from the detailed description given below, for information only and in no way limitative, and with reference to the appended drawings, in which:

FIG. 1 is an exemplary diagram of the equivalent electrical circuit of the protection device according to the invention;

FIG. 2 is an example of a sizing chart of the equivalent electrical circuit of the protection device according to the invention;

FIG. 3 is an example of a protection mesh implemented according to the invention;

FIGS. 4 and 5 respectively illustrate two examples of modes of operation of the protection device according to the invention. In the remainder of the description, the expression "substantially" will express a relationship of equality at plus or minus 10%.

The diagram of the equivalent electrical circuit 10 of the protection device according to the invention of Figure 1 comprises a first circuit 12 representative of the protective mesh used to protect at least a portion of an electronic card not shown. For example, such a portion of the electronic card to be protected comprises a storage memory of sensitive data (s) or a transceiver of sensitive data (s).

In addition, the equivalent electrical circuit 10 comprises an electronic measuring component 14 C_M connectable to the first circuit 12 representative of the protection mesh of the electronic card.

The protective mesh 12 and the electronic measurement component 14 form, once connected, a closed loop 16 whose electronic measurement component 14 continuously measures the inductance, the protective mesh 12 acting as a sensor for the electronic component measuring 14.

According to one particular aspect, the electronic measurement component 14 is an inductance-to-digital converter. For example, such an inductor-digital converter 14 corresponds to the active component, high resolution, and low power consumption, LDC1000 of Texas Instrument ™. Other electronic measurement components 14 such as LDC1041, LDC1051, LDC1 101, LDC1312, LDC1314, etc. are also possible.

More specifically, such active components are able to emit a modulated wave in the protection mesh, such a wave being necessary for the measurement of inductance. A modification of the inductance of the protection mesh 12, in particular in the event of a malicious intrusion, generates a modification of the measured signal (e.g. a modification of its frequency and envelope).

Such inductance-to-digital converters 14 usually use a coil or spring as an inductive sensor for non-contact detection of linear / angular position, displacement, motion, compression, vibration, metal composition, etc., conductive targets.

According to the present invention, the use of such an inductance-digital converter is diverted from its usual use. Indeed, according to the invention, the protective mesh 12 is directly the sensor of the inductance-to-digital converter 14 and the inductance-to-digital converter 14 only measures the variations in the inductance value of the protective mesh 12. In other words, because a protective mesh is a particular track to be characterized in particular by its inductance, the protective mesh 12 according to the present invention plays the role of the inductive sensor in the form of coil or spring usually used by an inductance-to-digital converter.

Thus, as illustrated on the equivalent circuit 10 of the protection device of FIG. 1, the equivalent circuit 12 of the protection mesh is an inductive circuit 12 comprising at least a first coil representative of the characteristic inductance of the protection mesh (ie by representative example of the copper track of the protection mesh).

In addition, according to the example of Figure 1, the inductive circuit 12 further comprises at least a first resistor R _S i forming with the first coil a first circuit 12 Rsi U series.

Furthermore, as shown in FIG. 1, the electronic measurement component 14 is connected in parallel with the capacitance capacitor capacitor C, the capacitor being connected in series, according to at least the closed loop 16, to at least said protection mesh. .

Depending on the type of electronic measurement component 14, in particular corresponding to an inductance-to-digital converter used, the same electronic measurement component 14 is adapted to be connected to a plurality of closed loops 16, not shown, for example to supervise the integrity several protection meshes respectively associated with several different areas of the electronic card to be protected.

For example, such an inductor-digital converter 14 is the component LDC1312.

In addition, in FIG. 1, the closed loop 16 formed of the electronic measurement component 14 and its sensor: the protective mesh 12 comprises, according to a particular aspect of the invention, a second coil L ₂ and a second resistor R _S 2 forming a second circuit 18 R _S 2I-2 series, connected in series both to capacitor capacitance value C and to the protection mesh corresponding to the first circuit 12 Rsi U series.

Such a second circuit 18 contributes to the dimensioning of the equivalent circuit 10 of the protection device according to the invention as detailed hereinafter in relation to FIG. 2.

Indeed, the dimensioning of the equivalent circuit 10 is adapted according to the electronic measurement component 14 used and / or according to the characteristics of the inductive circuit 12 equivalent to the protection mesh used (ie characteristics of this protection mesh). More precisely, the minimization, low consumption, reactivity and precision objectives condition the setting possibilities of the electronic measurement component 14, and the dimensioning of the equivalent circuit 10 according to the present invention takes into account these parameterization possibilities (ie operation of the measuring component 14).

In particular, the equivalent circuit 10 is, by its constitution as described above, a resonant circuit whose resonance frequency is: fres =

with L the inductance of the closed loop 1 6 (ie L = L _t + L ₂ ) and C the capacitance value of the capacitor.

Such a resonant frequency belongs to a predetermined frequency range and conditioned by the performance of the selected electronic measurement component 14.

For example, when the electronic measurement component 14, is the active component, high resolution, and low power consumption, Texas Instrument ™ LDC1000 this resonance frequency fres should be between 5kHz and 5MHz.

In view of this operating parameter (ie the resonance frequency) associated with the electronic measurement component 14, the sizing of the electronic components of the closed loop 1 6 of the equivalent circuit 1 0 of the protection device is based in particular on the use an abacus as illustrated in Figure 2.

On this chart associated with the electronic measurement component 14 corresponding to the LDC1000 of Texas Instrument ™ are represented, on the ordinate, values of the inductance L of the closed loop 1 6, on the abscissa, capacitance values C of the capacitor, and in FIG. settings :

the frequency resonance frequency fres of 5kHz, 10kHz, 100kHz, 1 MHz and 5MHz represented by a first group of parallel abacus lines,

or else the doublets formed of the quality factor Q and the impedance Rp value of the closed loop 16 with Rp = ^ - - ^ where R _s = R _sl +

R _s2 , represented by a second group of abacus lines parallel to each other.

Such a closed loop impedance belongs to a range of predetermined impedance values and conditioned by the performance of the selected electronic measurement component 14.

For example, when the electronic measuring component 14, is the active component, high resolution, and low power consumption, Texas LDC1000 Instrument ™, the impedance Rp value of the closed loop 16 measurable is between 798Ω and 3.93ΜΩ.

More precisely, the impedance Rp of the closed loop 16 corresponds to the parallel impedance equivalent to the series R _S LC electronic circuit of the closed loop 16.

Such an abacus makes it possible in particular to determine an inductance value L of the closed loop 16 and the capacitance value C of the associated capacitor, to ensure proper operation of the protection device according to the invention. In particular, the smaller the value C of the capacitor, the larger the impedance value of the closed loop 16 Rp. Furthermore, this same capacitance value C is limited, according to the invention, to be compatible with the oscillation frequency of the resonant analog circuit LC between 5 kHz and 5 MHz.

In other words, the values of the electronic components of the equivalent circuit 10 of the protection device according to the invention are selected in the range 20 of the chart corresponding to the proper operation of the electronic measurement component 14, while the values L, C of the zone 22 complementary to the range 20 of good operation of the abacus are prohibited to compose the equivalent circuit 10 of the protection device according to the invention. In other words, the zone 22 comprises the pairs of LC values that are incompatible with the specifications of the electronic measurement component 14 LDC1000.

Thus, according to the abacus of FIG. 2, an example of satisfactory sizing of the equivalent circuit 10 corresponds to the point P of the zone 20 of good operation of the abacus representative of the association of the frequency fres = 5 MHz, with the quality factor value Q = 25, the loop impedance value Rp = 798Ω, the loop inductance value L = ΙμΗ, and the capacitance value C = InF.

The second circuit 18 R _S 2L ₂ series makes it possible to increase the degree of freedom to adjust the dimensioning of the equivalent circuit 10 so that it conforms to the zone 20 of good operation of the chart.

In other words, if the equivalent inductance of the first circuit 12 representative of the protection mesh is too small to be compatible with the zone 20 of good operation of the electronic measuring component 14 LDC1000, it is necessary to add an inductor L ₂ in series with this one to enhance the value of the inductor seen from the LDC1000.

The protection device 10 according to the invention further comprises a microcontroller or a microprocessor, not shown, configured to drive the inductor-digital converter 14. Such a microcontroller, for example the Texas Instrument ™ MSP430 microcontroller, as well as the electronic measurement component 14 are located on the predetermined zone of the electronic card to be protected.

In the event of detecting a measured inductance variation greater than a predetermined threshold, such an inductance-to-digital converter 14 is able to transmit directly, via an output port, not shown, or to provide a module, not shown. , processing and / or data transmission of the microcontroller or the microprocessor of the protection device, an information representative of an inductance variation of the measured protection mesh.

For example, the LDC1000 is able to directly emit one or more representative alerts of the abnormal variation (s) of inductance of the measured protection mesh.

This information corresponds for example to an audible alert, the activation of a light, for example a light-emitting diode or LED (English light-emitting diode), or the simple change of state of a signal (eg change of binary state from 0 to 1, or level: high state, low state) managed by a higher level electronic map monitoring system, not shown.

For example, the inductance-to-digital converter 14 accounts for the modification of the inductance measured, for example by interruption on crossing a predetermined threshold (for example preprogrammed), or the microcontroller implements a polling (of English polling ) of the value measured by the inductance-to-digital converter 14.

According to a particular variant, not shown, the protection device of the present invention further comprises a user interface enabling the user to input the control instruction of the protection device 10 or even the restitution of the measured inductance data.

Thus, according to a layered structure, the layer (s) comprising the protection mesh, corresponding to the equivalent electrical circuit 12, is or is "superimposed (s)" above the predetermined zone of the electronic card to be protected. carrying the components and / or signals to be protected as well as the electronic measurement component 14 and the microcontroller or the microprocessor controlling it.

According to a particular aspect, in relation to FIG. 3, a global ground plane 24 (ie capable of covering the whole of the predetermined zone of the electronic card to be protected, in other words extending over a substantially equal surface at the deployment surface of the protective mesh 12) is inserted, such as an intermediate layer between the protective mesh 12 and the predetermined zone of the electronic card to protect. For example, in the context of protection of an electronic card, such an overall ground plane 24 is a solid copper plane constituting the multilayer printed circuit board (PCB).

Such a global mass plan 24 notably allows an optimization of the protection of the electronic card against a malicious intrusion.

Indeed, according to the present invention, the overall ground plane 24 and the protection mesh, represented by the equivalent circuit 12, are mutually coupled. The value of the equivalent inductance of the closed loop 16 measured by the electronic measurement component 14 is representative of such a coupling. Thus, the modification, for example by malicious deterioration, of the overall ground plane 24 will also be detected even if the protection mesh remains intact.

In other words, the coupling of the overall ground plane 24 to the protection mesh allows an optimization of the inductance measurements and thus the detection of an abnormal variation of inductance synonymous with a malicious intrusion.

In order to connect the layers respectively comprising, on the one hand, the protective mesh 12 and, on the other hand, the predetermined zone of the electronic card to be protected by means of via (ie holes making it possible to establish an electrical connection through different layers) are used, for example, and are adapted to traverse, if appropriate, the ground plane 24 inserted such as an intermediate layer between the protective mesh and the predetermined zone of the electronic card to be protected.

In other words, a stack in a vertical direction, not shown, is obtained from the upper layer (s) comprising the superimposed protection mesh (s) on the intermediate layer comprising the overall mass plane 24, itself superimposed on at least one lower layer comprising the predetermined area of the electronic card to be protected.

In addition, according to a particular aspect of the invention illustrated in FIG. 3, the protective mesh is able to comprise at least one monolayer portion 26 and / or at least one multilayer portion 28 superimposed on the ground plane 24.

In other words, in the part 26 the protection mesh is for example planar and therefore two-dimensional (i.e. 2D) while in the portion 28 the protection mesh is three-dimensional (i.e. 3D) because extended over several layers 30 and 32.

In particular, when the protective mesh comprises at least one multilayer part 28, the protective mesh is able to present in this part a pattern different from one layer 30 to the other 32 and / or a pattern rotation, for example at an angle of 90 ° from one layer to another. Indeed, an infinity of protection meshes are usable, or even combinable as long as the equivalent inductance of this mesh is significant, in other words measurable by the electronic measurement component 14, according to the invention namely:

- a serpentine pattern;

- a pattern in the form of boustrophedon (i.e. in zigzag);

- a snail-shaped pattern;

- a spiral pattern;

- a randomly generated pattern;

- etc.

By randomly generated pattern is meant a protection mesh pattern adapted to vary randomly from one protection device to another, and therefore not predictable by a malicious third party.

Each pattern is characterized by an inductance value of the first circuit 12 representative of the protection mesh that is specific to it. In other words, the pattern of the protection mesh, as well as its electromechanical environment notably comprising the ground plane 24, have an effect on the loop inductance 16 measured by the electronic measurement component 14.

In Figure 3, a serpentine pattern 30 of the protective mesh is shown in particular. In addition, the pattern 33 associated with a shunt intrusion is shown and zoomed.

Such a shunt 33 is introduced in place of a coil portion 30 and has a height h, for example equal to 2.5 mm substantially equal to the opening formed by deleting the corresponding portion of the coil but a width L, by example equal to 6mm smaller than the width of the portion of the serpentine protection mesh 30 removed so that it is easy to introduce to deteriorate or capture sensitive data of the electronic card to protect.

Such a shunt 33 makes it possible to ensure the continuity of the protection mesh and is undetectable by the protection devices of the state of the art specific only to detect, in a binary manner, the opening of the electric circuit equivalent to the mesh of protection, such an opening causing a voltage drop.

However, the shunt 33 shown in the figure has an inductance of its own, for example of the order of 20nH, which represents for example 0.5% of the inductance of the coil portion 30 removed. So, inserting such a shunt 33 causes a decrease in the inductance of the closed loop 16 of the protection device, a decrease detectable by the electronic measurement component 14.

FIGS. 4 and 5 respectively illustrate two exemplary modes of operation of the protection device according to the invention.

These two modes of operation associated with the component LDC1000 are known per se, however the usual use of this component for non-contact detection is specifically diverted according to the invention for intrusion detection in an electronic card protection mesh.

More precisely, these two figures show the loop inductance measurement L, or the measurement of another electrical quantity representative of the loop inductance L, for example the loop impedance Rp obtained continuously during the time t of a window of observation of the activity of the protection mesh and two thresholds respectively high 36 and low 38 of variation of the value 34 measured.

According to a first mode of operation of the protection device illustrated in FIG. 4, referred to as the "comparator mode" of the protection device, as soon as the measured value 34 passes the high threshold 36 (ie as soon as an abnormal variation of the inductance is measured), the output signal 40 (or interrupt command) generated by the electronic measurement component 14 changes its binary value (passing for example from 1 to 0) so that the microcontroller receiving such a value issues an alert indicating a intrusion.

When the measured value 34 then decreases to the lower threshold 38, the inverse change in binary value (i.e. deactivation of the interrupt command) is automatically implemented. In other words, a return to the initial state (i.e. the state of integrity) is again obtained.

In other words, according to this comparator mode, the protection device according to the invention behaves like a binary alerter able to detect a shunt within a protection mesh.

According to a second mode of operation of the protection device illustrated in FIG. 5, called the "alarm mode" or "memory effect mode" of the protection device, the electronic measurement component 14 also directly delivers an interface control signal 42. , the interface being capable of reproducing a signal 44 representative of an intrusion or the integrity of the operating mesh as a function of the value of the control signal 42.

In other words, in comparison with the first mode of operation previously described, to not miss furtive alerts in this second mode of operation, the state of alert restored by means of the signal 44 is preserved until its acknowledgment controlled by the signal 42.

In a particular aspect, the measurements implemented by the electronic measurement component 14 are cyclic.

Furthermore, a phase of calibration (or even self-calibration) of the electronic measurement component 14, implemented by the microcontroller not shown, is for example reiterated periodically so as to take account of drifts due to changes in the environment ( temperature, humidity ...) or the aging of the components (LDC1000, capacitors ....).

The electronic card protection device according to the invention therefore makes it possible to substantially improve the level of security of the electronic cards by making it possible to detect the shunts while being autonomous and integrated with the protection mesh and the electronic card to be protected.

Claims

1. - Device (10) for protecting an electronic card, the protection device being connectable to said electronic card, and comprising:

a protection mesh of at least one predetermined zone of the electronic card to be protected, and

an electronic measuring component (14) capable of being connected to the protective mesh used as a sensor of at least one electrical quantity passing through it,

the electronic measurement component (14) being configured to measure the inductance of the protection mesh, and, in case of detection of a variation in inductance greater than a predetermined threshold, configured to transmit, or to provide a processing module and / or data transmission of the protection device, an information representative of said variation of inductance.

2. - Protection device (10) according to claim 1, wherein the electronic measuring component (14) is an inductance-to-digital converter.

3. - Protection device according to any one of the preceding claims, wherein the equivalent circuit of the protective mesh is an inductive circuit (12) comprising at least a first coil () representative of the equivalent inductance of the protective mesh.

4. - Protection device according to claim 3, wherein the equivalent inductive circuit of the protection mesh (12) further comprises at least a first resistor (R _S i) representative of the equivalent resistance of the protective mesh forming with said first coil (L1) representative of the equivalent inductance of the protection mesh, a first circuit (12) Rsi Li series 5.- Protection device according to any one of the preceding claims, in which the electronic measuring component (14) is connected in parallel with a capacitor (C), the capacitor (C) being connected in parallel, in at least one closed loop (16), to at least said protective mesh 6.-Protection device according to claim 6, wherein the closed loop

(16) further comprises a second coil (L ₂ ) and a second resistor (R _S 2) forming a second series circuit (18) F, the capacitor (C) being connected in parallel with the first circuit (12) Rsi U equivalent series of the protection mesh, and in series with the second circuit (18) R _S 2 series. 7. Protection device according to claim 6 or 7, wherein the closed loop has an oscillation frequency (f _res ) belonging to a predetermined frequency range, and has a loop impedance (Rp) belonging to a range of predetermined impedance values, the oscillation frequency (f _res ) and the loop impedance (Rp) both conditioning the resistance (s), coil (s) and capacitor values of the electronic components of the closed loop ( 16).

8. - Protection device according to any one of the preceding claims, wherein the protective mesh has a pattern belonging to the group comprising at least:

- a serpentine pattern;

- a pattern in the form of boustrophedon;

- a snail-shaped pattern;

- a spiral pattern;

- a randomly generated pattern.

9. - protection device according to any one of the preceding claims, wherein the protective mesh is adapted to comprise at least one portion (26) monolayer and / or at least one portion (28) multilayered (s) superimposed on a ground plane (24).

10. - Protection device according to claim 9, wherein when the protective mesh comprises at least one portion (28) multilayer, the protective mesh of said portion is adapted to have a different pattern from one layer to another and / or pattern rotation and / or pattern shift from one layer to another.