• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:
    The present invention relates to a method for securing data transmitted by a data source (2) of a connected object (1) against attacks on a control circuit (4) of the connected object (1), the object connected device (1) further comprising an electronic signature circuit (6) and a communication bus (8) connected to the control circuit (4), connected to the electronic signature circuit (6) and connected to the source (2), in which the method comprises the following steps implemented by the electronic signature circuit (6): • detection (602) of a first data item (M) transmitted by the source (2) on the communication bus (8), Detection (606) of a second data item (M ') to be signed on the communication bus, the second datum having been transmitted (404) by the control circuit (4) on the communication bus (8) following a detection by the control device (4) of the first data item (M), • verification (608) of a coherent between the detected data (M, M '), signaling (610) or not an error (E), according to a result of the verification
    公开号:FR3076639A1
    申请号:FR1850080
    申请日:2018-01-05
    公开日:2019-07-12
    发明作者:Kurt Louis Bonnin Frederick；Pierre Bernard Jean-Yves；Emmanuelle Dottax；Fabien BLANCO
    申请人:Idemia Identity and Security France SAS；
    IPC主号:
    专利说明:

    FIELD OF THE INVENTION
    The present invention relates to a method of securing data within a connected object against attacks affecting a control circuit of the connected object.
    STATE OF THE ART
    A conventional connected object includes a sensor configured to acquire measurement data, and a communication interface for transmitting such measurement data to a remote server.
    Such a connected object generally comprises a control circuit configured to request the sensor to supply it with such measurement data, and to transmit from. such measurement data at the communication interface for retransmission by the latter to the remote server.
    The control circuit and the sensor communicate with each other by a communication bus.
    To certify that the data transmitted to the server originates from the connected object, the connected object electronically signs the measurement data before their transmission to the server using a secret key specific to the connected object.
    Such an electronic signature could be implemented by the control circuit itself. However, in many connected objects, the control circuit is insecure. This implies in particular that the control circuit is liable to be the object of remote attacks coming from outside the connected object, these attacks taking the form of data relayed by the communication interface. The attacker could then discover the secret key.
    It has been proposed to add a separate secure circuit from the control circuit in the connected object. The application of an electronic signature is thus delegated to this secure circuit. This solution has several advantages over the solution of modifying the control circuit so as to make it more secure. First, the secure circuit is less exposed than the control circuit to attacks from the communication interface; the secret key is therefore more difficult to discover. Secondly, this solution offers the possibility for a manufacturer of connected objects without specific security skills to integrate into one of their products a secure circuit provided by a third party.
    However, the addition of a secure circuit complicates the internal architecture of the connected object.
    A relatively complex architectural modification would consist in particular in arranging the secure circuit between the control circuit and the sensor, without direct connection between the control circuit and the sensor. In this way, all measurement data would first be electronically signed by the secure circuit before being transmitted to the control circuit.
    However, such complexification could make it difficult to integrate a secure circuit provided by a third party into a preexisting connected object.
    To limit these architectural complexity problems caused by the addition of this secure circuit, it is advantageous to simply connect the secure circuit to the communication bus already existing between the control circuit and the sensor.
    However, this particular choice poses a new problem: with such an architecture, the secure circuit is not in a position to ensure the authenticity of the measurement data transmitted by the sensor.
    STATEMENT OF THE INVENTION
    An object of the present invention is therefore to improve the resistance of a connected object to attacks aimed at compromising a certification of data intended to be emitted by the connected object, without however greatly complicating the architecture of the object. logged.
    It is therefore proposed, according to a first aspect of the invention, a method for securing data transmitted by a data source of a connected object against attacks affecting a control circuit of the connected object, the connected object comprising also an electronic signature circuit and a communication bus connected to the control circuit, linked to the electronic signature circuit and connected to the source, in which the method comprises the following steps implemented by the electronic signature circuit: • detection of a first datum transmitted by the source on the communication bus, • detection of a second datum to be signed on the communication bus, the second datum having been transmitted by the control circuit on the communication bus following a detection by the first data control device, • verification of consistency between the detected data, • reporting or not an error, based on a check result.
    Preferably, the following steps are implemented by the electronic signature circuit: • detection of a request asking the source to send data different from the first data, • inhibition of the request preventing the request from being processed by the source, • transmission on the communication bus of a dummy data in response to the request, • detection of a third data to be signed on the communication bus, the third data transmitted by the control circuit on the bus communication, the third datum having been sent by the control circuit on the communication bus following a detection by the control device of the dummy datum, • verification of a consistency between the third datum and the dummy datum previously transmitted, • reporting of an error or not, depending on a result of the consistency check between the third datum and the facti datum this.
    Preferably, the inhibition comprises: the emission of a command to deactivate the source, or else the emission of a command to modify a destination address for requests stored by the source to a value different from a destination address contained in the request, or a change on the fly from a destination address contained in the request to a value different from a destination address for requests from the source.
    Preferably, only part of the bits at the destination address contained in the request is modified, the modified part consisting of a least significant bit or of several least significant bits of the destination address.
    Preferably, the electronic signature circuit implements the following steps: • detection of a sequence of N consecutive requests requesting the source to send data, where N> 1, • selection of K requests among the N consecutive requests detected, where K <N, • implementation of the inhibition step only on the K requests selected.
    Preferably, the selection is random.
    Preferably, K = N-1.
    Preferably, the method according to the first aspect comprises a generation, by the electronic signature circuit, of the dummy data from at least one data previously transmitted by the source.
    Preferably, the dummy data results from a modification of only part of the bits of the data previously transmitted by the source, the modified part consisting of a least significant bit or several least significant bits of the data previously transmitted by the source.
    Preferably, the following steps are implemented by the electronic signature circuit: • measurement of at least one physical characteristic of a signal circulating on the communication bus while the control circuit transmits data or a request on the communication bus, the physical characteristic being for example a signal voltage or a duration between two predetermined signal edges, • comparison of the physical characteristic measured with a predetermined template, and signaling or not of an error, according to a result of the comparison between the physical characteristic and the gauge, or • calculation of a confidence index representative of a conformity of the physical characteristic measured with the gauge, and report of the confidence index.
    Preferably, the source is a sensor, and the data emitted by the sensor are measurement data acquired by the sensor.
    It is also proposed, according to a second aspect of the invention, an electronic signature circuit configured to: • be connectable to a communication bus to which are also connected a control circuit and a data source of a connected object, • detect a first datum sent by the source on the communication bus, • detect a second datum to sign on the communication bus, the second datum having been sent by the control circuit on the communication bus following a detection by the first data control device, • check the consistency of the detected data, • report an error or not, depending on the verification.
    There is also proposed, according to a third aspect of the invention, a system for securing data transmitted by a data source of a connected object, the system comprising an electronic signature circuit according to the second aspect of the invention, and a control circuit configured to: • be connectable to the communication bus, • detect the first data sent by the source on the communication bus, • send the second data on the communication bus to be signed by the electronic signature circuit.
    There is also proposed, according to a fourth aspect of the invention, a connected object comprising a data source, a system for securing data transmitted by the source which is in accordance with the second aspect of the invention, and a communication bus, wherein the sensor, the control circuit and the electronic signature circuit are connected to the communication bus.
    DESCRIPTION OF THE FIGURES Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which should be read with reference to the appended drawings in which: • Figure 1 illustrates in a way schematically a system comprising a connected object and a server, according to an embodiment of the invention; • Figures 2 to 8 are flowcharts of steps in a data security process implemented by the connected object illustrated in Figure 1.
    In all of the figures, similar elements bear identical references.
    DETAILED DESCRIPTION OF THE INVENTION
    With reference to FIG. 1, a connected object 1 comprises a data source 2, a control circuit 4, an electronic signature circuit 6, a communication bus 8, and a communication interface 10 with a remote server 3.
    The data source 2 is connected to the communication bus 8, and is capable of transmitting data on this bus 8.
    In the following, it will be considered, without limitation, that the data source 2 is a sensor.
    The sensor 2 is configured to acquire measurement data representative of a physical quantity, for example temperatures.
    The sensor 2 comprises a measurement processing unit 12 configured to detect and process measurement requests originating from the communication bus 8, as well as transmitting data on the communication bus 8.
    The sensor 2 includes an internal register 14 in which is stored an address which is specific to it. This address makes it possible to distinguish the sensor 2 from other equipment connected to the communication bus 8.
    The sensor 2 can include an address modification port 16, making it possible to receive a command adapted to modify the value of the address stored in the internal register 12.
    The sensor 2 can moreover comprise a deactivation port 18, and be capable of being deactivated or reactivated by appropriate signals received by the deactivation port.
    The control circuit 4 is also connected to the communication bus 8. It performs a role of master, that is to say that it is capable of controlling the sensor 2 and the electronic signature circuit 6 by means of requests passing by bus 8, as we will see later.
    The control circuit 4 comprises a data processing unit 20, for example at least one processor, or at least one microprocessor.
    The control circuit 4 is also configured to know the address of the sensor 2. It has for example a memory 22 in which this address of the sensor 2 is stored. As a variant, the memory 22 is external to the control circuit.
    The electronic signature circuit 6 comprises a data processing unit 24 (for example at least one processor, or at least one microprocessor) configured to electronically sign data acquired by the sensor 2 in a manner which will be described later. In the present text, it is considered that an "electronic signature" designates any processing modifying, marking or supplementing data so as to certify that the data to be signed has been acquired within the connected object 1.
    The electronic signature circuit 6 also includes a memory 26 in which a secret key which can be used to implement such an electronic signature is stored.
    The electronic signature circuit 6 is connected to the communication bus 8. The electronic signature circuit 6 has its own address on the communication bus 8. This address makes it possible to distinguish the signature circuit from other equipment connected to the bus communication 8, in particular sensor 2.
    The electronic signature circuit 6 can also include an input / output port -GPIO connected to the deactivation port of the sensor 2 or to the address modification port of the sensor 2, via a line independent of the communication bus 8.
    The communication bus 8 is for example a bus 8 of the l2C type (Inter-integrated Circuit, in English). In a manner known in itself, the bus 8 then comprises a bidirectional data line SDA (“Serial Data Line”), and a bidirectional synchronization clock line SCL (“Serial Clock Line”). Each of the lines can take a low state (0) or a high state (1).
    As indicated previously, the control circuit 4, the sensor 2 and the electronic signature circuit 6 are connected simultaneously to the same communication bus 8 by independent physical links. In other words, we exclude the case where the control circuit 6 could communicate with the sensor 2 only via the electronic signature circuit 6. The network communication interface 10 is for example of wireless radio type, for example Wi-Fi , LoRaWan or Bluetooth. The network communication interface 10 is arranged to be able to communicate within the connected object 1 with the control circuit 4, for example via a link independent of the communication bus 8. Thus, the control circuit 4 can transmit data to the communication interface 10 for transmission to the server 3, or receive data from the communication interface 10 from the server 3.
    The control circuit 4 is not secure, in the sense that the control circuit 4 is capable of being the object of remote attacks coming from outside the object ~ -connected 1, these attacks taking the form of data relayed by the network communication interface 10.
    On the other hand, the electronic signature circuit 6 is secure in the sense that it has means of protection against such attacks.
    With reference to FIGS. 2 to 5, a method implemented by the connected object 1 comprises the following steps.
    By convention, the steps of the process implemented by a component of the connected object 1 have in these figures numerical references, the first digit of which corresponds to the numerical reference of the component implementing them. Thus the steps illustrated in FIGS. 2, 3 and 4 have references starting respectively with 4, 2 and 6 and are those implemented respectively by the control circuit 4, the sensor 2 and the electronic signature circuit 6. The figure 5 is a more general view of the method, which how the steps implemented by the components 2, 4 and 6 of the connected object 1 are coordinated.
    The control circuit 4 sends on the communication bus 8 a first measurement request RM1 asking the sensor 2 to send measurement data (step 400).
    The first request includes in particular the address specific to the sensor 2, so as to signify that the first request sent on the communication bus 8 is intended to be processed by the sensor 2.
    When the communication bus 8 is a PC bus, this first measurement request RM1 results in a succession of state changes of the two lines of the bus 8, this succession being determined by the PC communication protocol, known in itself .
    The sensor 2 detects the first measurement request RM1 sent on the communication bus 8 (step 200). During detection 200, the sensor 2 compares the address included in the first measurement request RM1 and compares it with the address stored in its internal register. As the two addresses are identical, sensor 2 processes the first request. If the two addresses were different, the sensor 2 would deduce therefrom that the first request is intended for another slave device connected to the communication bus 8, and therefore would not process this request.
    The processing of the first request by the sensor 2 comprises the acquisition of a first measurement data M (step 202), and the transmission of the data acquired on the communication bus 8 in response to the first measurement request RM1 (step 204). It should be noted that acquisition 202 is not necessarily made after receipt of the request; this can have been done before said reception, asynchronously.
    The measurement data M is sent on the bus 8 (step 204) in the form of a response to the first request, the response having a predetermined format. It is not mandatory that this response includes any address of the control circuit 4 in the case where only the control circuit 4 is master on the communication bus 8 (which is supposed to be the case here); in fact the format of the response may be sufficient to make the control circuit 4 understand that this response is intended for it.
    The electronic signature circuit 6 detects the first measurement data having passed over the communication bus 8 (step 602).
    The electronic signature circuit 6 stores in its memory 26 the first measurement data (step 604).
    The control circuit 4 also detects the response having passed on the communication bus 8 (step 402).
    The control circuit 4 then transmits on the communication bus 8 a second measurement data item M ’to be electronically signed by the electronic signature circuit 6 (step 404). When the control circuit 4 is in a normal state, the second measurement data transmitted corresponds to the first data. However, when the control circuit 4 has been attacked, its behavior may be altered to the point that the second measurement data is different from the first measurement data previously detected by the control circuit 4.
    For example, the second measurement data item M ’is sent in a signature request RS1 further comprising the address of the electronic signature circuit 6 on the communication bus 8.
    The electronic signature circuit 6 detects the signature request RS1 having passed on the communication bus 8 (step 606). If the address of the RS1 signature request contains an address corresponding to its own address, which normally should be the case, the electronic signature circuit 6 processes the RS1 signature request; otherwise, the electronic signature circuit 6 does not process the RS1 signature request.
    The electronic signature circuit 6 checks whether the second measurement data M ’that it has received and the first measurement data M that it had previously stored in its memory 26 are consistent or not (step 608).
    In the present text, it is considered that two data are "coherent" if these two data are linked by a predetermined mathematical relation, and "incoherent" otherwise. This predetermined mathematical relationship can be equal, in which case the verification implemented by the electronic signature circuit 6 during step 608 is a comparison between the two data M and M ’. However, a more complex mathematical relationship can be verified by the electronic signature circuit 6 during step 608, if for example the control circuit 4 is supposed to apply processing to the data item M it receives.
    If the two compared measurement data M and M 'are incoherent, this means that the control circuit 4 has corrupted the first measurement data M that it received during step 402. It is therefore possible that the circuit 4 has been attacked. Consequently, the electronic signature circuit 6 signals in this case an error E (step 610). The error E is for example signaled to the control circuit 4, so that the control circuit 4 relays this error E to the server via the network communication interface 10 (step 406). The error E can be returned to the server spontaneously by the electronic signature circuit 6, when the two compared measurement data M and M ’are inconsistent. As a variant, this error E is raised to the server in response to a request sent by the server and received by the object connected via its network communication interface 10.
    If the two compared measurement data M and M ’correspond, this means that the control circuit 4 has not corrupted the first measurement data that it received. In this case, no error is reported.
    The electronic signature circuit 6 also applies an electronic signature to the second measurement data received from the control circuit 4, by means of the secret key stored in its memory, so as to produce a signed measurement data S (step 612) .
    The signed measurement data is then transmitted by the electronic signature circuit 6 to the control circuit 4 in response to the signature request, via the communication bus 8 (step 614).
    The control circuit 4 then triggers the transmission of the signed measurement data S to the server via the network communication interface 10 (step 408). The fact that the measurement data S has been signed electronically within the connected object 1 certifies to the server that this data S indeed comes from the connected object 1 and not from another device, or that this data has not modified by a device interposed between the server and the connected object 1 and implementing an attack by the man in the middle.
    The process steps can be repeated for several measurement requests sent to the sensor 2 sent sequentially by the control circuit 4 on the communication bus 8 (by repeating step 400).
    An advantage of the above method resides in the fact that it is fairly effectively secured against attacks affecting the control circuit 4. In fact, the electronic signature is entrusted to another component, which is more difficult to bypass via an attack .
    Another advantage of this process lies in its ease of implementation very easily on a basic connected object comprising the control circuit, the bus and the sensor, but not comprising a secure component. The only hardware modification to operate in such a basic connected object is in fact to connect such a secure component to the existing communication bus.
    The foregoing method is however not protected against certain particularly elaborate attacks affecting the control circuit 4. The control circuit 4 having been the subject of an attack could indeed act on the communication bus 8 so that the first measurement data M is corrupted during its transit on this bus 8, before being detected by the control circuit 4 during step 402. In the case for example where the communication bus 8 is a PC bus , the compromised control circuit 4 could impose a given value (for example 0 or 1) on the SDA data line, which would have the consequence that the first measurement data stored by the electronic signature circuit 6 would have this imposed value, as well as the second measurement data to be signed sent by the control circuit 4. Thus, the two measurement data M and M 'compared by the electronic signature circuit 6 would be identical and no error would be reported even though the control circuit was attacked.
    To avoid missing the detection of such an attack, and thus improve the security of the process, the following steps can advantageously be implemented, when the control circuit 4 sends on the communication bus 8 a second measurement request RM2 requesting the sensor 2 to supply another measurement data (during another implementation of step 400).
    The first measurement request RM1 and the second measurement request RM2 are two measurement requests sent consecutively by the control device on the communication bus 8. The second request RM2 can therefore be a measurement request which follows the first request RM1, or that precedes it.
    The electronic signature circuit 6 detects the second measurement request RM2 on the communication bus 8 (step 600).
    Following this detection 600, the electronic signature circuit 6 implements an inhibition processing preventing the second request RM2 from being processed by the sensor 2 (step 601).
    This inhibition step 601 can be declined in several variant embodiments.
    In a first variant, the inhibition 601 comprises the transmission by the electronic signature circuit 6 of a command to deactivate the sensor 2 to the deactivation port 18. When the sensor 2 receives this deactivation command on its deactivation port 18, the sensor 2 goes into a deactivated state in which the sensor 2 is unable to process the second request. This deactivated state is for example a de-energized state. Alternatively, the deactivation command can be sent to a component different from the sensor 2 but configured to cease supplying power to the sensor in response to reception of the deactivation command.
    In a second variant, the inhibition 601 comprises a modification on the fly of the destination address of the second measurement request RM2 to a value different from the address of the sensor 2. When the second request RM2 with a modified address arrives at sensor 2, sensor 2 considers that this second request RM2 is not intended for it since the address that this second request RM2 contains is different from the address stored in its internal register 14. An advantage of this second variant over the first variant is that it can be implemented when the sensor 2 does not include a deactivation port 18.
    The modification on the fly can for example consist in modifying only part of the bits of the destination address contained in the second request, the modified part consisting of a least significant bit or several most significant bits weak of the destination address. The modified part comprises for example 3 bits. This second variant is particularly easy to implement when the bus 8 is of the PC type.
    In a third variant, the inhibition comprises a transmission of an address modification signal to the address modification port of the sensor 2. On receipt of this modification command, the sensor 2 modifies the value of the address stored in its internal register at a value different from that which the control circuit 4 inserted in the second request. In this way, sensor 2 can only ignore the second request, which it considered as not being intended for it.
    This third variant has the advantage of further strengthening the level of security of the process compared to the second variant. Indeed, the control circuit 4 having been the subject of a particularly elaborate attack could detect, by inspecting the state of the communication bus 8, that the control circuit 4 modified on the fly the address of the request according to the second variant.
    Whatever the variant of inhibition 601 implemented, the sensor 2 is prevented from transmitting measurement data in response to the second request on the communication bus 8. Instead, the electronic signature circuit 6 generates a dummy measurement data D, and transmits this dummy measurement data on the communication bus 8 in response to the second request (step 603), so that the control circuit 4 believes that this dummy measurement data has been transmitted by the sensor 2. For this, the electronic signature circuit 6 uses a response format which imitates that used by the sensor 6 during step 204.
    The electronic signature circuit 6 also stores the dummy measurement data that it sent on the communication bus 8 in its memory 26 (step 605).
    Preferably, the dummy measurement data D is generated from at least one measurement data previously transmitted by the sensor 2, for example the data M, which makes it possible to strengthen the credibility of the dummy measurement data D with the control circuit 4. In other words, it becomes more difficult for the control circuit 4 to realize that the electronic signature device has passed itself off as the sensor 2.
    For example, the dummy measurement data D results from a modification of a part - only bits of a measurement data M previously transmitted by the sensor 2, the modified part consisting of a most significant bit weak or of several least significant bits of the measurement data M previously transmitted by the sensor 2. This modification modifies only very little the data previously transmitted, which makes identity theft carried out by the signature circuit electronics 6 during steps 601, 603 almost undetectable by the control circuit 4.
    The control circuit 4 detects the dummy measurement data D transmitted on the communication bus 8 (in a new implementation of step 402).
    In response to this detection, the control circuit 4 therefore transmits on the communication bus 8 a third measurement data item D ’to be electronically signed by the electronic signature circuit 6 (new implementation of step 404). The third measurement data D 'therefore corresponds to the dummy measurement data D when the control circuit 4 is in a normal state, but may not correspond to the dummy measurement data D'when the control circuit 4 is attack.
    The electronic signature circuit 6 detects the third measurement datum D ’(in a new implementation of step 606).
    In response to this detection, the electronic signature circuit 6 checks whether the third measurement data D ′ detected and the dummy measurement data D that it has stored in its memory 26 are consistent or not (step 607). This step 607 is for example identical to the step 608 previously described.
    If the two compared measurement data D and D ’are inconsistent, this means that the control circuit 4 has corrupted the dummy measurement data D that it received. It is therefore possible that the control circuit 4 has been attacked. Consequently, the electronic signature circuit 6 in this case signals an error E (in a new implementation of step 610). The error E is for example signaled to the control circuit 4, so that the control circuit 4 relays this error to the server via the network communication interface 10 (in a new implementation of step 406).
    If the two compared measurement data D and D ’are consistent, this means that the control circuit 4 has not corrupted the dummy measurement data that it received. In this case, no error is reported.
    Whatever the result of this consistency check, the electronic signature circuit 6 does not apply an electronic signature to the third measurement datum received from the control circuit 4, nor does it issue a response to the request for signature of the third data on the communication bus 8. It follows that the control circuit 4 does not transmit a signed version of the dummy measurement data to the server via the network communication interface 10.
    As a variant, the signature circuit applies an electronic signature to one of the two data, for example that coming from the control circuit 4 or that coming from the sensor 2, whatever the result of this consistency check.
    Ultimately, for two measurement requests RM1 and RM2 sent consecutively by the control circuit 4 and intended for the sensor 2, the control circuit 4 received a measurement data item M truly emitted by the sensor 2, and a dummy measurement data item D emitted by the electronic signature circuit 6 having passed itself off as the sensor 2.
    This principle can be generalized to any sequence of N measurement requests sent by the control circuit 4, where N> 1.
    For example, the electronic signature circuit 6 can detect a sequence of N consecutive measurement requests asking the sensor 2 to send measurement data (by repeating step 600 times N). For each measurement request detected, the electronic signature circuit selects or not the measurement request. If the request is selected, the inhibition step 601 is implemented, as well as the step 603 of emission of a dummy measurement data. If the request is not selected, the electronic signature circuit 6 does not filter the measurement request, as a result of which the sensor 6 transmits real measurement data in response to the measurement request after having detected it.
    The signature circuit selects K requests to filter from the N measurement requests, - where K <N. K can be predetermined, or be variable. In the case where K is variable, the electronic signature circuit 6 can decide whether or not to select a signature request by making a random draw, so that a request is selected with a predetermined probability P (in the case where P = 0.5, we obtain statistically K "N / 2).
    Consequently, the control circuit 4 ultimately receives NK measurement data genuinely emitted by the sensor 2, and K dummy measurement data emitted by the electronic signature circuit 6. This logic makes it possible to space the inhibitions operated relatively regularly. by the electronic signature circuit 6 over time, and therefore to "drown" the real measurement data among dummy data.
    Advantageously, the selection of the K requests is random. This random selection makes it possible to further reinforce the undetectability of the preceding mechanism of usurpation by the electronic signature circuit 6 of the sensor 2, near the control circuit. _.
    Subsequently, the control circuit 4 sends N signature requests intended for the electronic signature circuit 6 corresponding to the N responses it has received (dummy or not), in an order corresponding to the order in which the N requests for measurement were previously sent by the control circuit 4. The electronic signature circuit 6 then performs N consistency checks sequentially: • NK consistency checks between a measurement data item sent by the control circuit 4 and a measurement data item issued by the sensor 2, • K consistency checks between a datum sent by the control circuit 4 and a dummy memorized datum.
    The electronic signature circuit 6 knows whether the consistency check 607 or the consistency check 608 is to be implemented for this or that signature request, since it has memorized the order of the measurement requests that it has previously filtered (this storage can be carried out by means of a counter which counts the measurement requests sent by the control circuit 4). Another way for the electronic signature circuit 6 to determine whether or not a signature request which it receives relates to a dummy datum, is to ensure that the dummy data have values different from the values that the measurement data can have reassembled by sensor 2.
    Preferably, the electronic signature circuit 6 only implements the step of signaling 612 of an error E once the N consistency checks have been carried out, in the case where at least one of the consistency checks finds an inconsistency of values. .
    In one embodiment, K = N-1 is chosen. In this case, for N requests for measurements sent consecutively by the control circuit 4 and intended for the sensor 2, the control circuit 4 receives a single measurement datum truly emitted by the sensor 2, and N-1 dummy measurement data emitted by the electronic signature circuit 6 which pretended to be the sensor 2. In this way, each measurement data item emitted by the sensor is effectively protected.
    The above steps are repeated by the electronic signature circuit 6 for other sequences of N consecutive requests.
    Of course, the inhibition implemented by the electronic signature circuit 6 for a given request is intended to last only temporarily. When the electronic signature circuit decides during step 601 not to select a measurement request subsequent to the measurement request RM2 (and therefore not to inhibit it), it is done so that the sensor 2 is returned to a state enabling it to process this subsequent uninhibited request. Thus, according to the variant of inhibition chosen, it can be provided for this purpose that the signature circuit 6: • emits a command to reactivate the sensor 2, • emits a command to restore the address stored in the internal register of the sensor 2 has the value used elsewhere by the control circuit to request measurements, • does not modify on the fly the address of the measurement request detected during step 600.
    The method is advantageously supplemented by the following additional steps implemented by the electronic signature circuit 6, in order to detect fraudulent behavior by the control device 4.
    The electronic signature circuit 6 measures at least one physical characteristic of a signal circulating on the communication bus 8 while the control circuit 4 sends a request on the communication bus 8 (signature request or measurement request).
    This physical characteristic is for example a signal voltage or a duration between two predetermined edges of the signal (typically times between edges on the SDA line compared to those of the edges of the SCL line, in the case of a bus 8 of l2C type communication). The measurement step is for example carried out by means of an analog-digital converter of the electronic signature circuit 6 connected to the communication bus 8.
    Next, the electronic signature circuit 6 compares the physical characteristic measured with a predetermined template.
    If the physical characteristic measured does not comply with the template, an error is signaled by the electronic signature circuit 6. Otherwise, no error is reported.
    The template can be determined by the electronic signature circuit 6 during a prior learning step, during which it is considered that the control circuit 4 is not compromised, and during which the signature circuit acquires signals emanating from from bus 8, and builds the template from these signals. This learning step can be carried out at the factory, or be triggered when the connected object 1 is switched on for the first time, or at the request of the server. In addition, the template generated by a connected object 1 can optionally be copied into other identical connected objects.
    Furthermore, the signature circuit can calculate a confidence index representative of a degree of conformity of a measurement acquired with the corresponding template, and report this confidence index to the server in place of the error (or else in addition to thereof).
    Such a score provides richer information than a simple error. As a result, the server has the ability to take different actions, depending on the value of the trust it receives.
    By sending a confidence index, the server is also able to take actions (alert or deactivation of connected objects) based on the multiple indices collected on different connected objects.
    In the case where the control circuit 4 of the connected object 1 is compromised with a high attacking potential, this same control circuit 4 could be capable of practicing the same learning on the responses of the electronic signature circuit 6, and thus imitating it non-detectably by the electronic signature circuit 6. To counter such an attacker, the electronic signature circuit 6 can modify the characteristics of the signal, so that the signals possibly analyzed by the control circuit 4 do not are not representative of the responses provided by the electronic signature circuit 6. The imitations used by the control circuit 4 will then be detected by the electronic signature circuit 6, since they do not have the real characteristics of the signals sent by the signature circuit electronic 6.
    权利要求:
    Claims (16)
    [1" id="c-fr-0001]
    1. Method for securing data transmitted by a data source (2) of a connected object (1) against attacks affecting a control circuit (4) of the connected object (1), the connected object (1 ) further comprising an electronic signature circuit (6) and a communication bus (8) connected to the control circuit (4), connected to the electronic signature circuit (6) and connected to the source (2), in which the method comprises the following steps implemented by the electronic signature circuit (6): • detection (602) of a first datum (M) transmitted by the source (2) on the communication bus (8), • detection ( 606) of a second datum (M ') to be signed on the communication bus, the second datum having been transmitted (404) by the control circuit (4) on the communication bus (8) following a detection by the control device (4) of the first datum (M), • verification (608) of consistency between the donations born (Μ, M ’) detected, • reporting (610) or not of an error (E), depending on a verification result.
    [2" id="c-fr-0002]
    2. Method according to claim 1, further comprising the following steps implemented by the electronic signature circuit (6): • detection (600) of a request (RM2) asking the source (2) to send a data different from the first data, • inhibition (601) of the request (RM2) preventing the request (RM2) from being processed by the source (2), • transmission (603) on the communication bus (8) of a dummy datum (D) in response to the request, • detection (606) of a third datum (D ') to be signed on the communication bus (8), the third datum (D') sent by the control circuit (4) on the communication bus (8), the third datum (D ') having been transmitted (404) by the control circuit (4) on the communication bus (8) following a detection by the control device (4) of the dummy datum (D), • verification (607) of a consistency between the third datum (D ') and the dummy datum (D) previously issued, • reporting (610) or not of an error (E), depending on a result of the consistency check between the third datum and the dummy datum.
    [3" id="c-fr-0003]
    3. The method of claim 2, wherein the inhibition (601) comprises issuing a deactivation command of the source (2).
    [4" id="c-fr-0004]
    4. Method according to claim 2, in which the inhibition (601) comprises a transmission of a command to modify a destination address of requests stored by the source (2) to a value different from a destination address. contained in the request (RM2).
    [5" id="c-fr-0005]
    5. Method according to claim 2, in which the inhibition (601) comprises a modification on the fly from a destination address contained in the request to a value different from a destination address for requests from the source (2). .
    [6" id="c-fr-0006]
    6. Method according to claim 5, in which only part of the bits the destination address contained in the request is modified, the modified part consisting of a least significant bit or of several least significant bits. of the destination address.
    [7" id="c-fr-0007]
    7. Method according to one of claims 2 to 6, in which the electronic signature circuit (6) implements the following steps: • detection of a sequence of N consecutive requests requesting the source (2) to transmit data, where N> 1, • selection of K requests from the N consecutive requests detected, where K <N, • implementation of the inhibition step only on the K requests selected.
    [8" id="c-fr-0008]
    8. The method of claim 7, wherein the selection is random.
    [9" id="c-fr-0009]
    9. Method according to one of claims 7 and 8, wherein K = N-1.
    [10" id="c-fr-0010]
    10. Method according to one of claims 2 to 9, comprising a generation, by the electronic signature circuit (6), of the dummy data from at least one data previously transmitted by the source (2).
    [11" id="c-fr-0011]
    11. The method of claim 10, wherein the dummy data results from a modification of only part of the bits of the data previously transmitted by the source (2), the modified part consisting of a most significant bit. low or several least significant bits of the data previously transmitted by the source (2).
    [12" id="c-fr-0012]
    12. Method according to one of claims 1 to 11, comprising the following steps implemented by the electronic signature circuit (6) • measurement of at least one physical characteristic of a signal circulating on the communication bus (8 ) while the control circuit (4) transmits a data or a request on the communication bus (8), the physical characteristic being for example a signal voltage or a duration between two predetermined edges of the signal, • comparison of the characteristic physical measured with a predetermined template, and reporting or not of an error, according to a result of the comparison between the physical characteristic and the template, or • calculation of a confidence index representative of a conformity of the characteristic physical measurement, and reporting of the confidence index.
    [13" id="c-fr-0013]
    13. Method according to one of claims 1 to 12, wherein the source (2) is a sensor, and the data transmitted by the sensor are measurement data acquired by the sensor.
    [14" id="c-fr-0014]
    14. Electronic signature circuit (6) configured to: • be connectable to a communication bus (8) to which are also connected a control circuit (4) and a data source (2) of a connected object (1 ), • detect a first datum (M) sent by the source (2) on the communication bus (8), • detect a second datum (M ') to sign on the communication bus, the second datum having been sent ( 404) by the control circuit (4) on the communication bus (8) following detection by the control device (4) of the first datum (M), • checking a consistency of the data (Μ, M ') detected, • report an error or not (E), depending on the verification.
    [15" id="c-fr-0015]
    15. System for securing data transmitted by a data source (2) of a connected object (1), the system comprising an electronic signature circuit (6) according to claim 14, and a control circuit (4) configured to: • be connectable to the communication bus (8), • detect the first data sent by the source (2) on the communication bus (8), • send the second data to be signed on the communication bus (8) by the electronic signature circuit (6).
    [16" id="c-fr-0016]
    16. Connected object (1) comprising a data source (2), a system for securing data transmitted by the source (2) according to claim 15, and a communication bus (8), in which the sensor (2) , the control circuit (4) and the electronic signature circuit (6) are connected to the communication bus (8).
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    US20190215234A1|2019-07-11|
    US11165633B2|2021-11-02|
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    WO2017046805A1|2015-09-17|2017-03-23|Tower-Sec Ltd.|Systems and methods for detection of malicious activity in vehicle data communication networks|
    CN107562559A|2017-08-29|2018-01-09|郑州云海信息技术有限公司|The method of testing and device of data consistency between controller system memory|
    CN110912766B|2019-10-18|2021-04-20|国家计算机网络与信息安全管理中心|Communication network multi-plane data consistency checking method|
    法律状态:
    2019-04-30| PLFP| Fee payment|Year of fee payment: 2 |
    2019-07-12| PLSC| Publication of the preliminary search report|Effective date: 20190712 |
    2019-12-19| PLFP| Fee payment|Year of fee payment: 3 |
    2020-01-10| CA| Change of address|Effective date: 20191205 |
    2020-12-17| PLFP| Fee payment|Year of fee payment: 4 |
    2021-12-15| PLFP| Fee payment|Year of fee payment: 5 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1850080|2018-01-05|
    FR1850080A|FR3076639B1|2018-01-05|2018-01-05|METHOD AND SYSTEM FOR SECURING DATA EMITTED BY A CONNECTED OBJECT AGAINST ATTACKS AFFECTING A CONTROL CIRCUIT OF THE SAID OBJECT|FR1850080A| FR3076639B1|2018-01-05|2018-01-05|METHOD AND SYSTEM FOR SECURING DATA EMITTED BY A CONNECTED OBJECT AGAINST ATTACKS AFFECTING A CONTROL CIRCUIT OF THE SAID OBJECT|
    US16/240,149| US11165633B2|2018-01-05|2019-01-04|Method and system for securing data transmitted by a connected object against attacks affecting a control circuit of said object|
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