WO2016051059A1

WO2016051059A1 - Method of protecting a mobile terminal against attacks

Info

Publication number: WO2016051059A1
Application number: PCT/FR2015/052579
Authority: WO
Inventors: Mohamed SABT; Mohammed Achemlal
Original assignee: Orange
Priority date: 2014-09-30
Filing date: 2015-09-28
Publication date: 2016-04-07
Also published as: FR3026528A1

Abstract

The invention relates to a method of detecting an attack aimed at a mobile terminal (10), the terminal comprising a security element (12), a contactless controller (13) suitable for dialoguing with a contactless reader (20) and a secure execution environment (11), in which: - any command (C-APDU) originating from the contactless reader and received by the contactless controller is dispatched to the secure execution environment and to the security module, and - any command (C-APDU) received by the security element is dispatched to the secure execution environment, the method comprising a step of verification (E14), implemented by the secure execution environment, in the course of which it is verified that to a command (C-APDU) received from the contactless controller there corresponds a same command (C-APDU) received from the security element, in the converse case a software attack of relay type is detected.

Description

Method of protecting a mobile terminal against attacks

The present invention relates to a method of protecting a mobile terminal against attacks, more precisely against attacks of the relay type.

It finds a particularly interesting application in securing sensitive services, such as payment services on smart mobile terminals.

An intelligent smartphone-type mobile terminal in English, adapted to execute sensitive contactless services, such as a "Near Field Communication" (NFC) type payment service, conventionally security (or "SE" of the English "Secure Element"), for example a "SIM" card (Subscriber Identity Module) and an NFC controller. The NFC controller is arranged to communicate with a connected NFC reader, as part of a payment transaction, to a merchant terminal. The security element is suitable for storing sensitive data and applications. In the case of payment transactions, the security element stores cryptographic data of secret key types or private keys, sensitive applications; access to sensitive operations of the application, or even access to the payment application itself, is conditioned by the user entering a personal identification code (usually referred to as code " PIN ", of the English" Personal Identification Number "). When the user wishes to initiate a payment transaction at a merchant, he approaches his mobile terminal of the NFC reader located at the merchant and the payment application located in the security element runs between the terminal and the server by the user. the intermediary of the reader and the NFC controller, the transaction information being exchanged between the payment application and the NFC reader using "Application Protocol Data Unit" (APDU) frames. At the end of the transaction, the user's account is debited with the amount of the transaction.

Such an architecture is however sensitive to relay type attacks. To set up such an attack, an attacker installs malicious software on the mobile terminal of the victimized user to redirect data to the attacker's mobile terminal. This installation is performed for example by means of a Trojan horse, apparently legitimate software from the point of view of the mobile terminal of the victim and which includes malicious software. The malware is arranged to listen and record data exchanged with the security element during legitimate payment transactions. In particular, sensitive data such as the personal identification code entered by the legitimate user to validate a payment transaction can thus be accessible to the malicious software. For example, the personal identification code may be requested at the user when executing a security function such as a signature function that requires access to a signature private key stored in the security module.

The attacker also installs control software on his own mobile terminal. The control software is arranged to control the actions of the malicious software installed on the victim's terminal and cleverly relay, via the Internet, information from the victim's terminal to the attacker's terminal or the terminal of the victim. attacker to the victim's terminal.

Thus, in a first example of attack, the attacker initiates a payment transaction at a merchant. The exchanges between the security element of the attacker's terminal and the payment terminal, via the reader and the NFC controller, are relayed by the attacker's terminal control software to the malicious software installed on the terminal of the attacker. the victim. The malware controls the execution of the payment application of the victim's mobile terminal. When the personal identification code needed to access a sensitive function of the security element of the victim is requested during the transaction, the malware transmits it without the victim being requested. The responses of the security element of the victim are thus relayed by the malware to the terminal of the attacker who transmits them to the merchant's payment terminal via the NFC controller. Neither the merchant nor the victim realize that an attack is taking place. However, the victim's account is debited instead of the attacker's account. Such a relay attack thus allows the attacker to buy goods by debiting the victim's account.

In a second example of an attack, the attacker steals loyalty point data intended for the victim, specifically intended to be stored in the security element of the victim. In this case, it is the victim who initiates a transaction with a merchant through a contactless reader. Loyalty points that are transmitted at the end of the transaction by the merchant to the victim's terminal via the reader and the NFC controller are relayed, via the Internet, by the malware installed on the victim's terminal to the mobile terminal of the victim. the attacker to be registered in the attacker's security element.

These attacks are possible because of the Internet connectivity of smart terminals. One of the aims of the invention is to remedy the shortcomings / disadvantages of the state of the art and / or to make improvements thereto.

To this end, the invention proposes a method for detecting an attack on a mobile terminal, the terminal comprising a security element, a contactless controller adapted to communicate with a contactless reader and a secure execution environment, in which which : any command from the contactless reader received by the contactless controller is sent to the secure execution environment and the security module, and

- any command received by the security element is sent to the secure execution environment,

the method comprising a verification step, implemented by the secure execution environment, during which it is verified that a command received from the contactless controller corresponds to the same command received from the security element, in if not, a relay-type software attack is detected.

The described method thus makes it possible to detect relay-type software attacks. Indeed, it is verified that a command received from the NFC controller by the secure execution environment corresponds to the receipt by the secure execution environment of the same command from the security element.

It is usual for an attacker who wishes to implement a relay-type software attack to install malicious software on the mobile terminal of a victim, and on his own mobile terminal adapted control software to control the malware. In a first attack scenario, the attacker initiates a payment transaction with his own mobile terminal via his NFC controller. It relays commands received from the NFC player via its own controller to the victim's mobile terminal through the control software and malicious software installed on the victim's terminal. It is the payment application of the victim's mobile terminal that is executed that is thus executed. Thus, the security element transmits the command relayed by the attacker's mobile terminal control software to the secure execution environment of the victim's terminal. However, the secure execution environment does not receive the same command from the NFC controller. Indeed, the NFC controller of the victim is not involved in the transaction since it is the attacker who communicates with the NFC player in the context of the current transaction. The attack is therefore detected by the secure execution environment of the victim's terminal.

In a second attack scenario, the victim is executing a transaction during which loyalty points will be transmitted to the security element via the NFC controller of the victim's terminal. The malicious software controlled by the attacker terminal control software relays the commands relating to this transmission of loyalty points to the attacker's terminal. A command received by the NFC controller of the victim's mobile terminal is sent to the secure execution environment of the victim's terminal. However, this same command is not received from the victim's security element since it is processed by the attacker's security element. Thus, in these two scenarios, the non-reception by the secure execution environment of the same command by two different channels, in this case the secure execution environment / security element channel and the execution environment channel. secure / NFC controller, indicates that a relay-type software attack is in progress.

In an exemplary embodiment, the security element and the secure execution environment share the knowledge of a secret key, the method further comprising the following steps:

- calculation by the security element of a first control value, a function of the command received from the contactless controller and the secret key, and sending said first control value to the secure execution environment,

verification by the secure execution environment of the consistency between the first control value and the command received from the security element, a relay-type software attack being detected in the event of an inconsistency.

In this exemplary embodiment, the calculation of the first control value by the security element, a function of the secret key K and the C-APDU command received from the contactless controller, and the sending of this value to the secure execution environment, ensures that the command sent by the security element to the secure execution environment is the one that is received by this environment. In other words, the control value makes it possible to check the integrity of the communication channel that separates the security element from the secure execution environment which, by construction, is not secure. Remember that this link is not secure because the security module can in some cases be removable. This additional control provides an additional level of security in detection. Thus, it is ensured that it is the security element that shares the private key with the secure execution environment and is therefore in the same mobile terminal that sends the command.

In an alternative embodiment, the security element and the secure execution environment share knowledge of a secret key, the method further comprising the steps of:

- reception by the secure execution environment from the security element of the response,

reception by the secure execution environment from the contactless controller of the response to the command received from the security element by the controller,

- calculation by the security element of a first control value, a function of the response received from the contactless controller and the secret key and sending said first control value to the secure execution environment, verification by the secure execution environment of the coherence between the first control value and the response received from the security element, a relay-type software attack being detected in the event of an inconsistency.

In this exemplary embodiment, the first control value is calculated based on the private key and the response determined by the security element. This example is an alternative to the example described above.

In another exemplary embodiment, which calculates the first control value by the security element is also a function of a response to said command determined by the security element and that the method comprises the following steps:

checking the consistency between the first control value and the commands and responses received from the security element,

if the verification is positive, comparing the response received from the security element with the response received from the contactless controller, a relay-type software attack being detected if the verification is negative or if the comparison is negative.

In this example, the first control value is calculated from the command and the response determined by the security element. The level of security is therefore higher than when the control relates to a single type of frame.

Advantageously, the method comprises, when no relay-type software attack has been detected:

a step of obtaining, by the secure execution environment from a terminal location module, geographic location coordinates of the mobile terminal,

a step of comparing said geographical location coordinates of the terminal with geographical location coordinates of the reader, a relay-type hardware attack being detected when the coordinates of the terminal and the reader differ from a value greater than a given threshold value.

The process steps described here make it possible to detect particular attacks, in this case, hardware attacks of the relay type. This type of attack is more complicated to implement for an attacker because it requires to install a probe in the mobile terminal of a potential victim. This probe is intended to relay to or from the attacker's terminal information that passes over a communication link that connects the NFC controller to the secure execution environment. With the process steps described here, it is ensured that it is the secure execution environment that is in the mobile terminal that communicates with the NFC controller.

The invention also relates to a mobile terminal comprising a security element, a contactless controller adapted to communicate with a contactless reader, and a secure execution environment, and:

first sending means, arranged to send any command from the contactless reader and received by the contactless controller to the secure execution environment and the security module,

second means of sending, arranged to send any command received by the security element to the secure execution environment,

first verification means, arranged to verify that to a command received from the contactless controller corresponds the same command received from the security element, a relay-type software attack is detected in the event of a negative verification.

In another embodiment of the mobile terminal, the security element and the secure execution environment share the knowledge of a secret key, the terminal further comprising:

means for calculating and sending, arranged so that the security element calculates a first control value, a function of the command received from the contactless controller and the secret key, and to send said first control value to the secure execution environment,

second verification means, arranged so that the secure execution environment checks the consistency between the first control value and the command received from the security element, a relay-type software attack being detected in the event of an inconsistency .

In another embodiment, the mobile terminal further comprises:

a geolocation module, arranged to provide the secure execution environment with the geographical coordinates of the mobile terminal,

means for receiving geographical coordinates of the reader, arranged to receive geographical coordinates of the reader,

comparison means, arranged for, when no relay attack has been detected, comparing the coordinates of the mobile terminal with the geographic coordinates of the reader, a hardware attack being detected when the coordinates of the terminal and the reader differ from a value greater than a given threshold value.

The invention also relates to a computer program on a data carrier and loadable in the memory of a mobile terminal, the program comprising instructions for code for performing the steps of the attack detection method according to the invention, when the program is executed on said computer.

The invention also relates to a data carrier in which the program according to the invention is recorded.

Other features and advantages of the present invention will be better understood from the description and the appended drawings in which:

FIG. 1 is a schematic representation of an architecture adapted to implement the steps of an attack detection method, according to a first embodiment of the invention;

FIG. 2a presents the steps of a method of detecting software attacks of relay type, according to a first embodiment of the invention;

FIG. 2b presents the steps of a method for detecting hardware attacks, according to an embodiment of the invention;

FIG. 3 is a functional schematic representation of a mobile terminal, according to an exemplary embodiment of the invention.

An architecture adapted to implement the steps of the attack detection method, according to a first embodiment of the invention, will now be described in relation to FIG.

In this architecture, a mobile terminal 10 conforms to the specifications proposed by the GlobalPlatform association, or conforms to similar approaches. The GlobalPlatform specifications define a mobile terminal architecture where two execution environments coexist: a secure execution environment 11, or "TEE" (Trusted Execution Environment ") and an unsecured execution environment, or "REE" (of the English "Rich Execution Environment") (not shown in Figure 1). The secure execution environment 11 is independent of the unsecured execution environment. It is intended to provide a software and hardware environment for secure applications. It is considered trusted and relies on its own resources: a secure operating system, secure software modules and secure hardware resources, such as security features such as secure storage, communication interfaces with components security, etc. The secure execution environment 11 is arranged to provide security services to the unsecured execution environment through predefined interfaces. It is known from the GlobalPlatform specifications that the operating system of the secure runtime environment 11 is run from a trusted firmware (we speak of "firmware" in English) which is authenticated and isolated from the unsecured operating system during the boot process (we speak of "boot" in English). Once the firmware is authenticated, the secure operating system 11 is executed and the secure execution environment 11 is established. During this establishment, the secure runtime environment 11 initializes the firmware, imports cryptographic data such as keys, certificates, signatures, and configures certain devices to ensure security during communications between the runtime environment. secure 11 and these devices. After the establishment of the secure execution environment 11, the control is transmitted to the unsecured execution environment. Terminal startup then continues with an unsecured operating system run and an establishment during this execution of the unsecured execution environment. If the user next selects a secure application, the system switches to the secure runtime environment and runs the application in that secure environment. Upon completion of the application execution, the system switches back to the unsecured execution environment.

The mobile terminal 10 also comprises a security element 12. The security element 12 is for example a "UICC" card (for "Universal Integrated Circuit Card"), such as a subscriber identity card or "SIM" card. ("Subscriber Identity Module"), removable or welded (so called "embedded SIM"). In another embodiment, the security element is a microSD-type removable component ("SD" for Sandisk®). In another exemplary embodiment, the security element is a secure software zone. The security element 12 is designed to store sensitive applications or functions, for example a payment application, functions and cryptographic data such as signature functions, secret keys, etc. The payment application includes code instructions for implementing some of the steps of the attack detection method. In an exemplary embodiment, the payment application is stored in the secure execution environment 11 and uses one or more sensitive functions stored in the security element 12, for example a signature function which requires, for unlock access to a private key signature, the entry by the user of a correct PIN. In another exemplary embodiment, the payment application is stored in the security element 12. The mobile terminal 10 also comprises a contactless controller, for example an "NFC" controller 13 ("Near Field Communication" ) Arranged to allow contactless communication with a contactless reader, for example an NFC reader 20 connected to a remote server 21, for example the server of a merchant. When the payment application is executed, it dialogs with a merchant application that runs in the server 21 via the NFC controller 13 and the reader NFC 20. The NFC controller 13 comprises code instructions for implementing those steps of the attack detection method that are executed by the NFC controller 13. In an exemplary embodiment, the mobile terminal 10 also comprises a module for geolocation, for example a "GPS" module 16 (of the "Global Positioning System") intended to provide location coordinates of the mobile terminal. The geographical coordinates provided by the geolocation module 16 are expressed for example by a pair (X, Y) where X represents the latitude in degrees, minutes, seconds and thousandths of seconds and Y the longitude in degrees, minutes, seconds and thousandths of seconds. second. In an exemplary embodiment, the geographic location technique used by the module 16 is differential; this technique is more accurate than a standard GPS location.

It is assumed that when starting the secure execution environment 11, the latter has configured the NFC controller 13 and the GPS module 16 if necessary, so as to guarantee the security of the communications that it establishes with these devices. Thus, from a software point of view, the exchanges between the secure execution environment 11 and the NFC controller 13 on the one hand, and between the secure execution environment 11 and the GPS module 16 on the other hand are supposedly secure.

It is furthermore assumed that in an exemplary embodiment, the security element 12 and the secure execution environment 11 share the knowledge of a secret key K intended to guarantee that commands received from the NFC reader 13 and responses that are transmitted in response to the reader 20 come from the security module of the mobile terminal that is performing the transaction.

When executing the payment application that resides in the secure execution environment 11 or in the security element 12, information relating to the transaction is transported in APDU ("Application Protocol") format. Data Unit ") between the NFC reader 20, the secure execution environment 11 and the security element 12, via the NFC controller 13.

The steps of an attack detection method on a mobile terminal, according to a first embodiment of the invention, will now be described in relation with FIG. 2a.

A user equipped with a mobile terminal 10 according to the description presented in the architecture described in connection with FIG. 1 wishes to execute a contactless application, such as an NFC payment application stored in the security element 12 of its terminal. mobile 10. In a preliminary configuration phase, a secret key K, shared by these two entities, has been installed in the security element 12 and in the secure execution environment 11 of the mobile terminal 10. In an exemplary embodiment, the installation was made in the factory, before the mobile terminal 10 is marketed. In another embodiment, the secret key K has been installed after the terminal 10 has been placed on the market. For example, it has been installed in the security element 12 by means of an "OTA" procedure. English "Over The Air") and in the secure execution environment 11 through a similar procedure via the 3G or 4G Internet network.

In an initial step (not shown), the user, equipped with his mobile terminal 10 approaches the NFC reader 20 to perform a transaction without contact. In an exemplary embodiment, the NFC reader 20, located in a station, allows the user to buy train tickets using his mobile terminal 10. Approaching the mobile terminal 10 of the NFC reader 20 triggers the execution of a payment application stored in the security element 12 of the mobile terminal 10. In another embodiment, the user of the mobile terminal 10 triggers the execution of the payment application by selecting it in a menu , then approaches its mobile terminal 10 of the NFC reader 20. There is then established a dialogue between the payment application stored in the security element 12 and a payment module (not shown in Figure 2) of the merchant stored in the remote server 21, via the NFC reader 20 and the NFC controller 13 of the terminal 10. The information exchanged during this dialogue, in the form of commands and responses, are transported in "APDU" frames (" Application Protocol Data Unit ").

In a command sending step E1, a C-APDU command is sent from the server 21 to the security element 12, more precisely to the payment application located in the security element 12, via the NFC reader 20. and the NFC controller 13. The C-APDU is received by the NFC controller 13 in a receiving and retransmitting step E2, and then transmitted to the security element 12. The C-APDU command is received by the security 12, more precisely by the payment application stored in the security element 12, in a receiving step E3. The C-APDU command is for example a request for data: request for confirmation of the amount of the ticket, request for confirmation of the journey, request for validation of payment, etc.

This C-APDU command is processed by the security element 12 in a processing step E4. The security element 12 determines an R-APDU response following this processing. For example, if the received C-APDU command is a path confirmation request, a message is displayed to the user who confirms the path or not. The response R-APDU then comprises the response of the user. If the C-APDU command is a message from payment validation, the user is asked to enter a service PIN. Entering a correct PIN triggers the execution of a security function, for example a signature of the payment information relating to the current transaction, by means of a signature private key stored in the security element 12. In this case, the R-APDU response determined by the security element 12 is a message that includes the signature of the payment information.

In a step E5 of calculating a first control value, the security element 12, more precisely the payment application, calculates a first control value a. The first control value a is calculated by applying a cryptographic function f to the C-APDU command received from the NFC controller 13 during the receiving step E3, and to the R-APDU response determined by the security element 12. The cryptographic function f is parameterized by the secret key K shared by the security element 12 and the secure execution environment 11. The cryptographic function f is for example a "MAC" type authentication function. English "Message Authentication Code"), for example the "HMAC" (for "Keyed-Hashed MAC") function, or the "CMAC" (for "Cipher-based MAC") function. The first control value a is intended to enable the secure execution environment 11 to check the integrity of the C-APDU command and the R-APDU response that were processed by the security element 12. Control is justified by the fact that the communication link between the secure execution environment 11 and the security element 12 is, by construction, not secure. Such a control is therefore intended to ensure the integrity of the communication channel between the security element 12 and the secure execution environment 11.

In a parameter sending step E6, the security element 12 sends to the secure execution environment 11 a set of parameters which comprises the first control value a, the C-APDU command received by the security element. security 12 during step E3 and the R-APDU response that it determined during the processing step E4. This set of parameters is received by the secure execution environment 11 in a receiving step E7.

In a sending step E8, the determined R-APDU response is sent by the security element 12 to the NFC controller 13. It is received by the NFC controller 13 in a reception step E9.

In a transaction information sending step E10, the NFC controller 13 sends information about the current transaction to the secure execution environment 11. In this example, the NFC controller 13 sends the C-APDU command that it received from the NFC reader 20 during the receiving step E2 and the R-APDU response to that command that it has. received from the security element 12 during the reception step E9. The C-APDU command and the R-APDU response are received by the secure execution environment 11 in a receiving step El i.

In an integrity checking step E12, the secure execution environment 11 checks the integrity of the C-APDU command and the R-APDU response received from the security element 12 during the step E7 reception. For this purpose, it calculates a second control value a 'by applying the same cryptographic function f as that applied by the security element 12 during the step E5 of calculating the first control value a to the command C- APDU and R-APDU response received from security module 12 during step E7. The cryptographic function f is parameterized with the same secret key K. If the two control values are different, that is to say if a ≠ a '(branch "nok" in FIG. 2), this means that the data sent by the security module 12 differ from those received by the secure execution environment 11. This may be the case when the first control value has been calculated by means of a secret key different from that used by the environment. 11 to calculate the second control value α ', or when the C-APDU and R-APDU commands received from the security element 12 differ from those used by the security element 12 to calculate the first control value a. This may mean that it is not the security module 12 present in the mobile terminal 10 that has calculated the first control value a. In this case, the process ends in an end step E13, which terminates the current transaction. In an optional next step (not shown in FIG. 2), an information message is displayed to the user and / or sent by the secure execution environment 11 to the NFC reader 20.

In a second case where the two control values are identical, that is to say where a = a '(branch "ok" in FIG. 2), this means that the C-APDU command and the R-APDU response sent by the security element 12 are those that have been received by the secure execution environment 11. In this case, in a verification step E14, the secure execution environment 11 verifies that the commands C- APDUs and the R-APDUs responses received on the one hand from the security element 12 during the step E7 and on the other hand from the NFC controller 13 during the step El i are identical. In a first case where they are different ("nok" branch in FIG. 2), this means that the C-APDU command and / or the R-APDU response received from the NFC controller 13 are different from the C-APDU command and / or the R-APDU response received and processed by the security element 12. In this case, a relay attack is in progress. The process ends in the end step E13, which terminates the current transaction. In an optional next step (not shown in FIG. 2), an information message is displayed to the user and / or sent by the environment. 11. In a second case where the C-APDUs and the R-APDUs respectively received from the NFC controller 13 and the security element 12 are identical (branch "ok" in FIG. ), it is considered that there is no relay software attack in progress on the mobile terminal 10. The transaction can continue. The secure execution environment 11 informs the NFC controller 13 in an information step E15. The NFC controller 13 may send the R-APDU response to the server 21 via the NFC reader 20 in a response step E1 and a new command (not shown) may be received from the server 15 via the reader 14 and the controller 13 and processed. as previously described.

The steps described above make it possible to detect that no relay-type software attack is in progress. However, there is a risk that an attack that is more difficult to implement may be in progress. This attack is qualified as hardware attack because it requires to install a probe on a communication bus that connects the secure execution environment 11 to the security element 12. The steps described in connection with FIG. 2b, optional, are implemented to detect a relay type hardware attack when no relay type software attack has been detected. They are implemented after the comparison step E14 and in the case where the comparison is positive (branch "ok" in FIG. 2).

When it is desired to detect such a hardware attack, in a coordinate query step E17, implemented when the first and second control values a and a 'are identical, the secure execution environment 11 requests the module to GPS location 16 the geographical coordinates (X, Y) of the mobile terminal 10. This request is received by the GPS location module 16 in a step El 8 of reception. The GPS location module 16 sends the geographical coordinates of the mobile terminal 10 in a step E19 sending geographical coordinates. The geographical coordinates are received by the secure execution environment 11 in a receiving step E20.

In a comparison step E21, the secure execution environment 12 compares the geographical coordinates (X, Y) of the mobile terminal 10 with the geographical coordinates (Χ ', Y') of the NFC reader 20. In an exemplary embodiment, the geographical coordinates (Χ ', Y') of the NFC reader 20 are provided by the reader 20 to the NFC controller 13 at the beginning of the execution of the payment application. They are transmitted from the NFC controller 13 to the secure execution environment 11 spontaneously, or on request from the secure execution environment 11 in a preliminary step not shown in FIG. 2. The comparison between the coordinates (X, Y) of the mobile terminal and the coordinates (Χ ', Y') of the NFC reader 20 is positive if the difference between the two sets of coordinates (X, X ') and (Y, Y' ) is below a predefined threshold. Below this threshold, it is considered that the geographic location data associated with the mobile terminal 10 and the geographical coordinates (Χ ', Y') of the NFC reader 20 are sufficiently close to each other that the it is considered that the mobile terminal 10 and the NFC reader 14 are the two devices that are actually involved in the current transaction. In a location system where the coordinates include latitude and longitude expressed in degrees, minutes, seconds and thousandths of a second, a predefined threshold may consist in allowing variations only of the order of ten thousandths of a second for latitude and longitude, which is about thirty centimeters.

In a first case where the difference between the two sets of coordinates is less than the predefined threshold (branch "ok" in FIG. 2), then it is confirmed that no relay attack is in progress. The secure execution environment 11 informs the NFC controller 13 in the information step E15. The NFC controller 13 may send the R-APDU response to the server 21 via the NFC reader 20 in a response step E1 and a new command (not shown) may be received from the server 15 via the reader 14 and the controller 13 and processed. as previously described.

In a second case where the difference is greater than the predefined threshold, ("nok" branch in FIG. 2), then a relay type hardware attack is considered to be in progress since the terminal 10 and the NFC reader 14 are too far away. from one another to execute the current payment transaction. In this case, the process stops in the end step E13, which terminates the current transaction. In an optional next step (not shown), an information message is displayed to the user and / or sent by the secure execution environment 11 to the NFC reader 20.

The relay-type hardware attack is, however, complicated to implement. The optional steps E17 to E21 thus make it possible to ensure that it is indeed the secure execution environment 11 of the mobile terminal 10 that compares the first and second control values and that provides the result of this comparison to the NFC controller.

In a second exemplary embodiment (not shown in FIG. 2), the control performed by the secure execution environment 11 during the steps E12 and E14 relates only to the C-APDU command. Thus, the first control value a is calculated by the security element 12 during the step E5 by applying the cryptographic function f to the secret key K and the C-APDU command received from the NFC controller 13. In this example, only the first control value a and the command C-APDU are sent to the secure execution environment 11 during the step E6 sending control parameters. In the verification step E12, the second control value a 'is calculated by the secure execution environment 11 by applying the cryptographic function f to the secret key K and the C-APDU command received from the NFC controller. If the values are equal, then in step E14, only the C-APDUs commands received by the secure execution environment 11 on the one hand from the NFC controller 13 during the step El i and on the other hand of the security element 12 during the step E7 are compared. The method is here lighter to implement in that only C-APDU commands are compared. In an alternative embodiment, the control is similar to that described in this example except that it concerns the R-APDU response instead of the C-APDU command.

In a third exemplary embodiment (not shown in FIG. 3), a minimal control is implemented by the secure execution environment 11 in order to detect a relay attack. This check consists in ensuring that any C-APDU command received from the security controller 13 by the secure execution environment 11 corresponds to the same C-APDU command received from the security element 12 by the security environment. 11. In this embodiment, the step E5 for calculating the first control value a is not executed and the step E6 for sending parameters consists in sending the command C-APDU of the security element 12 to the secure execution environment 11. In this example, the NFC controller 13 sends the secure execution environment 11 in step E10 the C-APDU command. In an alternative embodiment, the C-APDU command may be sent by the NFC controller 13 to the secure execution environment 11 during the step E3, at the same time that it sends it to security element 12. In the example described here, the step E12 is not executed and the step E14 consists for the secure execution environment 11 to compare the C-APDU commands received respectively from the security element 12 and the NFC controller 13. A functional description of a mobile terminal 10 according to a first embodiment of the invention will now be provided in connection with FIG.

The mobile terminal 10 is a smart terminal type smartphone in English. It conforms to GlobalPlatform specifications. It thus comprises a secure execution environment 101, or TEE, and an insecure execution environment (not shown in FIG. 3). It also includes: a security element 12, adapted to host applications and / or sensitive functions. In an exemplary embodiment, it hosts a contactless payment application;

an NFC controller 11 adapted to communicate with the NFC contactless reader 20 (not shown in FIG. 3), the security element 12 and the secure execution environment 11, and to exchange information in the form of APDU frames;

where appropriate, a geolocation module 16 adapted to provide the geographical coordinates of the mobile terminal 10.

The secure execution environment 11 is an environment that operates in parallel with the unsecured execution environment. Security-sensitive applications are then executed either in the security element or in the secure execution environment. The secure execution environment provides security features such as secure storage space, secure application execution space, and secure management of input / output interfaces. Some communication channels are then natively secured by the secure execution environment 11, such as the TEE link / NFC controller 13, or the TEE / touch screen link (the touch screen is not shown in Fig. 3). On the other hand, the link TEE / element of security is, by construction not secured.

The mobile terminal 10 also comprises a set of resources described here in a simplified manner as being distributed between the different elements of the mobile terminal 10. This simplified description is consistent with the description of the method in which it is considered that the steps are implemented in the mobile terminal. Thus, schematically, the mobile terminal 10 comprises:

a processing unit 101, or "CPU" for "Central Processing Unit", 101-1, a set of memories, including a volatile memory 102 and a storage memory 103. The volatile memory 102 is arranged to execute code instructions , store variables, etc. The storage memory 103 is arranged to store security data such as keys, signatures, etc., where appropriate the secret key K, and a secure program comprising code instructions for implementing the steps. the method of detecting attacks as described above. It will be understood that, for example, the secret key K shared between the security element 12 and the secure execution environment 11 is stored in a first secure memory area specific to the security element 12 and a second memory zone secure, specific to the secure runtime environment 11. The mobile terminal 10 also comprises:

first sending means 104, arranged to send any C-APDU command from the NFC reader 20 and received by the NFC controller 13 to the secure execution environment 11 and the security element 12; second sending means 105, arranged to send any order C-

APDU received by the security element 12 to the secure execution environment i l;

first verification means 106, arranged to verify that a C-APDU command received from the NFC controller 13 corresponds to the same C-APDU command received from the security element 12, a relay-type software attack being detected in the case of negative verification.

In an exemplary embodiment, the mobile terminal 10 also comprises the following modules, in dashed lines in FIG. 3:

means 107 for calculating and sending, arranged so that the security element 12 calculates a first control value, a function of the C-APDU command received from the NFC controller 13 and the secret key K shared between the environment of the secure execution and the security element 12, and to send the calculated control value to the secure execution environment,

second verification means 108, arranged so that the secure execution environment 11 checks the coherence between the first control value and the command received from the security element 12, a relay-type software attack being detected in the event of 'inconsistency.

In an exemplary embodiment, the mobile terminal 10 also comprises:

means 109 for receiving geographic coordinates, arranged to receive from the reader 14 its geographical coordinates,

comparison means 110, arranged to compare, when no relay-type software attack has been detected, the coordinates of the mobile terminal 10 with the geographical coordinates of the reader 20, a hardware attack being detected when the coordinates of the mobile terminal 10 and the reader 20 differ by a value greater than a given threshold value.

The first sending means 104, the second sending means 105, the first checking means 106, the calculating and sending means 107, the second checking means 108, the geographic coordinate receiving means 109 and comparison means 110 are preferably software modules which comprise code instructions for executing the steps of the attack detection method as described previously. The software modules can be stored in, or transmitted by, a data carrier. This may be a hardware storage medium, for example a CD-ROM, a magnetic diskette or a hard disk, or a transmission medium, or a network.

Claims

1. A method of detecting an attack on a mobile terminal (10), the terminal comprising a security element (12), a contactless controller (13) adapted to communicate with a contactless reader (20) and a control environment. secure execution (11), wherein:

any command (C-APDU) coming from the contactless reader and received by the contactless controller is sent to the secure execution environment and the security module, and

- any command (C-APDU) received by the security element is sent to the secure execution environment,

the method comprising a verification step (El 4), implemented by the secure execution environment, during which it is verified that a command (C-APDU) received from the contactless controller corresponds to the same command (C-APDU) received from the security element, otherwise a relay type software attack is detected.

The method of claim 1, wherein the security element (12) and the secure execution environment (11) share knowledge of a secret key (K), the method further comprising the steps of:

calculation (E5) by the security element of a first control value (a), a function of the command received from the contactless controller and the secret key, and sending of said first control value to the environment of secure execution (11),

- Verification (El 2) by the secure execution environment of the consistency between the first control value and the command received from the security element, a relay-type software attack being detected in case of inconsistency.

The method of claim 1, wherein the security element (12) and the secure execution environment (11) share the knowledge of a secret key (K), the method further comprising the steps of:

- reception (E7) by the secure execution environment, from the security element of the response (R-APDU),

receiving (El i) by the secure execution environment, from the contactless controller of the response to the command received from the security element by the controller, calculation (E5) by the security element of a first control value (a), a function of the response received from the contactless controller and the secret key and sending of said first control value to the environment of secure execution (11),

- Verification (El 2) by the secure execution environment of the consistency between the first control value and the response received from the security element, a relay-type software attack being detected in the event of inconsistency.

The method according to claim 1 or claim 2, wherein the calculation of the first control value by the security element is also a function of a response (R-APDU) to said command determined by the security element. and that the method comprises the following steps:

receiving (El i) by the secure execution environment, from the contactless controller of the response to the command received from the security element by the controller,

checking (El 2) of the coherence between the first control value and the commands and responses received from the security element,

if the verification is positive, comparison (El 4) of the response received from the security element with the response received from the contactless controller, a relay-type software attack being detected if the verification is negative or if the comparison is negative .

5. Method according to one of the preceding claims, comprising, when no relay type software attack has been detected:

a step of obtaining (E20) by the secure execution environment from a terminal location module (16), geographic location coordinates of the mobile terminal,

a comparison step (E21) of said geographical location coordinates of the terminal with geographical location coordinates of the reader, a relay type hardware attack being detected when the coordinates of the terminal and the reader differ from a value greater than a threshold value; given.

A mobile terminal (10) comprising a security element (12), a contactless controller (13) adapted to communicate with a contactless reader, and a secure execution environment (11), and: first sending means (104), arranged to send any command (C-APDU) from the contactless reader and received by the contactless controller to the secure execution environment and the security module,

second sending means (105), arranged to send any command (C-APDU) received by the security element to the secure execution environment,

first verification means (106), arranged to verify that when a command received from the contactless controller corresponds to the same command received from the security element, a relay-type software attack is detected in the event of a negative verification.

The mobile terminal of claim 6, wherein the security element (12) and the secure execution environment (11) share the knowledge of a secret key (K), the terminal further comprising:

means (107) for calculating and sending, arranged so that the security element calculates a first control value (a), a function of the command received from the contactless controller and the secret key, and to send said first control value to the secure execution environment (11),

second verification means (108), arranged so that the secure execution environment verifies the coherence between the first control value and the command received from the security element, a relay-type software attack being detected in case inconsistency.

The mobile terminal of claim 6 or claim 7, further comprising:

a geolocation module (16), arranged to provide the secure execution environment with the geographic coordinates of the mobile terminal,

means (109) for receiving geographical coordinates of the reader, arranged to receive geographical coordinates of the reader,

comparison means (110), arranged for, when no relay attack has been detected, comparing the coordinates of the mobile terminal with the geographical coordinates of the reader, a hardware attack being detected when the coordinates of the terminal and the reader differ from a value greater than a given threshold value.

A computer program on a data carrier and loadable in the memory of a mobile terminal, the program comprising code instructions for performing the steps of the attack detection method according to one of claims 1 to 5, when the program is run on said computer.

10. Data carrier in which the program is recorded according to the claim