Method for authenticating mobile terminal for implementing payment application on mobile terminal

Abstract

The invention relates to a method (100) for authenticating a mobile terminal (TM) for implementing a payment application on said mobile terminal, said mobile terminal (TM) being configured to communicate with a server (S), said method (100) comprising the following steps implemented by said mobile terminal (TM):-issuing (111) to the server (S) a request to establish a trusted communication channel (CC); -receiving (112) an authentication request (RA) from said server (S), said authentication request being randomly selected by said server (S) from a predefined subset of a plurality of authentication requests, said authentication requests defining a list of features (LC) of said mobile terminal (TM),-collecting (113) a list of values (LV) of said mobile terminal (TM), and-sending said list of values (LV) of said mobile terminal (TM) to said server (S). Values in the value list correspond to features in a feature list (LC) of the mobile terminal (TM) sent by the server (S); -sending (114) the value list (LV) to the server (S), a trusted communication channel (CC) being established (216) by the server (S) from the value list (LV).

Description

[0001] The present invention relates to the field of payment applications, and more particularly to a software application configured to convert a commercial mobile terminal for the general public into a payment terminal.

[0002] It is known to convert a commercial mobile terminal (e.g. a smartphone, in particular of the smartphone type) intended for non-professional customers into a payment terminal using a software application that implements a method configured to authenticate the confidentiality of payment transactions performed by the mobile terminal.

[0003] This can only be authorized if the commercial mobile terminal meets the security standards. However, the mobile terminal cannot determine on its own whether it meets the security standards. A specific method implemented by the server is required to prove that the mobile terminal meets the standards.

[0004] The Payment Card Industry specifications do not describe how to develop and implement such an authentication method.

[0005] It is known to derive the required authentication from a set of information about the mobile terminal, which information is transmitted "in bulk" to a server.

[0006] However, this authentication method consumes a lot of processing power in the mobile terminal and requires a lot of time to collect data and transmit it to the server.

[0007] Therefore, the present invention aims to provide a solution to all or some of these problems.

[0008] To this end, the present invention relates to a method for authenticating a mobile terminal for implementing a payment application on the mobile terminal, the mobile terminal being configured to communicate with a server, the method comprising the following steps implemented by the mobile terminal:

[0009] - receiving an authentication request from a server, the authentication request being randomly selected by the server from a predefined subset of a plurality of authentication requests, the authentication request defining a list of characteristics of the mobile terminal,

[0010] - collecting a value list of the mobile terminal, the values ​​in the value list corresponding to the features in the feature list of the mobile terminal sent by the server;

[0011] - Send this list of values ​​to the server,

[0012] A trusted communication channel is established by the server based on the value list.

[0013] According to these provisions, since the server randomly selects a limited number of authentication requests from a large number of possible authentication requests, it is difficult for an attacker to design a mechanism to fraudulently determine the server's expected response. Therefore, the randomness of the selection of one or another mobile terminal's technical feature list from all possible technical feature lists provides protection against "man-in-the-middle" attacks.

[0014] According to these provisions, the method allows establishing a trusted communication channel that is implemented for a transaction phase that uses, for example, the trusted communication channel established for said transaction, such as a payment procedure.

[0015] According to one embodiment, the present invention comprises one or more of the following features, alone or in a technically acceptable combination.

[0016] According to one embodiment, the server encrypts the authentication request using a variable encryption key selected from a set of encryption keys of the server, each encryption key in the set of encryption keys corresponds to a decryption key of the mobile terminal, which is stored in a white box of the mobile terminal, and the method also includes a step of decrypting the encrypted authentication request using the decryption key of the mobile terminal stored in the white box of the mobile terminal.

[0017] According to one embodiment, the method further comprises a step of encrypting the value list using another variable encryption key of the mobile terminal stored in the white box of the mobile terminal, the encryption step producing an encrypted value list, the value list sent to the server during the transmission step being the encrypted value list.

[0018] According to one embodiment, the established trusted communication channel is secure.

[0019] According to one embodiment, the feature list of the mobile terminal includes at least one of at least one mobile terminal feature of the brand, model, and operating system version number of the mobile terminal.

[0020] According to one embodiment, the mobile terminal is a commercial device for the general public, such as a smartphone type, in particular a smartphone or a tablet computer.

[0021] According to one embodiment, the method further comprises the following steps performed after the trusted communication channel is established:

[0022] - receiving another authentication request from the server, the other authentication request being randomly selected by the server from the plurality of authentication requests, the other authentication request defining another feature list of the mobile terminal;

[0023] - collecting another value list of the mobile terminal, where the values ​​in the other value list correspond to the features in the other feature list of the mobile terminal;

[0024] - another transmission of the other list of values ​​to the server;

[0025] The communication channel is maintained or terminated by the server according to the other value list.

[0026] According to these provisions, since the number of authentication requests included in the plurality of authentication requests is large, each individual request may involve a small amount of information; therefore, the collection and transmission of this information by the mobile terminal will require limited computing power and workload. It should be noted that another authentication request in the predefined subset of the plurality of authentication requests defines another feature list for the mobile terminal.

[0027] According to one embodiment, the time at which the step of receiving another authentication request occurs depends on a time randomly determined by the server.

[0028] According to these provisions, the server randomly selects a small number of authentication requests from a large number of possible authentication requests, and the server issues these requests at randomly determined times, which makes it more difficult for attackers to design fraudulent mechanisms to determine the server's expected response.

[0029] According to one embodiment, the server encrypts other authentication requests using an encryption key of the server corresponding to a decryption key of the mobile terminal, the decryption key being stored in a white box of the mobile terminal, and the method further includes a step of decrypting the other encrypted authentication requests using the decryption key of the mobile terminal stored in the white box of the mobile terminal.

[0030] According to one embodiment, the method further comprises a step of encrypting the other list of values ​​using another variable encryption key of the mobile terminal stored in the white box of the mobile terminal, the encryption step generating another encrypted list of values, the other list of values ​​sent to the server during the other transmission being the other encrypted list of values.

[0031] According to one embodiment, the feature list of the mobile terminal includes at least one of the following features: the presence or absence of a specific software module in an application installed on the mobile terminal, the brand of the mobile terminal, the identification number of the mobile terminal, the version of the operating system installed on the mobile terminal, and the presence or absence of a certain file in a file system installed on the mobile terminal.

[0032] According to one aspect, the present invention also relates to a method for authenticating a mobile terminal for implementing a payment application on the mobile terminal, the mobile terminal being configured to communicate with a server, the method comprising the following steps implemented by the server:

[0033] - sending an authentication request to the mobile terminal, the authentication request being randomly selected by the server from a predefined subset of a plurality of authentication requests, the authentication request defining a feature list of the mobile terminal;

[0034] - receiving a list of values, the values ​​of which correspond to the characteristics of the mobile terminal in the list of characteristics sent by the server;

[0035] -determining the security level of the mobile terminal based on the value list;

[0036] -Establish a trusted communication channel based on the security level of the mobile terminal.

[0037] According to these provisions, the server randomly selects a limited number of authentication requests from a large number of possible authentication requests, which makes it difficult for an attacker to design a mechanism to fraudulently determine the server's expected response.

[0038] According to one embodiment, the present invention comprises one or more of the following features, alone or in a technically acceptable combination.

[0039] According to one embodiment, the method comprises a transaction phase which may implement, for example, a payment procedure using the trusted communication channel established by the method.

[0040] According to one embodiment, the method also includes a step of encrypting by the server using a variable encryption key selected from a set of encryption keys of the server, each encryption key in the set of encryption keys corresponds to a decryption key of the mobile terminal, and the decryption key is recorded in the white box of the mobile terminal, and the encrypted authentication request is decrypted using the decryption key of the mobile terminal recorded in the white box of the mobile terminal.

[0041] According to one embodiment, the method further comprises a step of decrypting by the server the encrypted list of values ​​using another server decryption key corresponding to the mobile terminal's variable encryption key stored in the mobile terminal's white box, the decryption step generating the list of values.

[0042] According to one embodiment, the trusted communication channel is established based on the security level of the mobile terminal and based on a delay between the receipt of the list of values ​​and the sending of the authentication request.

[0043] According to one embodiment, if the reception delay is greater than a predefined delay, or if the security level is below a predefined threshold, the server does not establish the communication channel.

[0044] According to one embodiment, the method further comprises the following steps performed by the server after the communication channel is established:

[0045] - sending at least one other authentication request, the at least one other authentication request being randomly selected by the server from the plurality of authentication requests;

[0046] - receiving another value list, wherein the values ​​in the other value list correspond to the characteristics in the other characteristic list of the mobile terminal;

[0047] - a further step of determining a further security level of the mobile terminal based on the further list of values;

[0048] - Maintain or terminate trusted communication channels based on other security levels.

[0049] According to these regulations, since the number of authentication requests included in the multiple authentication requests is large, each individual request may involve a small amount of information; therefore, the collection and transmission of this information by the mobile terminal will require limited computing power and load.

[0050] According to one embodiment, the step of sending at least one further authentication request occurs at a time randomly determined by the server.

[0051] According to these provisions, the server randomly selects a limited number of authentication requests from a large number of possible authentication requests, and the server issues these requests at randomly determined times, making it more difficult for an attacker to design a mechanism to fraudulently determine the server's expected response.

[0052] According to one embodiment, the server encrypts the further authentication request using a server encryption key corresponding to a decryption key of the mobile terminal, the decryption key being recorded in a white box of the mobile terminal.

[0053] According to one embodiment, the method further comprises a step of decrypting, by the server, the other encrypted value lists using another server decryption key stored in the white box of the mobile terminal corresponding to the variable encryption key of the mobile terminal, the decryption step generating the other value lists.

[0054] According to one embodiment, the communication channel is established based on a further security level of the mobile terminal and based on a further delay between the receipt of the further list of values ​​and the sending of the further authentication request.

[0055] According to another aspect, the present invention relates to a computer program comprising a set of instructions configured to implement a method according to one of the embodiments described above when the set of instructions is executed on a processor of a mobile terminal, or to implement a method according to one of the other embodiments described above when the instructions are executed on a processor of a server.

[0056] According to another aspect, the present invention relates to a mobile terminal comprising a processor and a memory, and a set of instructions recorded in the memory, wherein the set of instructions is configured to implement the method according to the above-described embodiments when the set of instructions is executed on the processor of the mobile terminal.

[0057] For a better understanding, embodiments and / or implementations of the present invention are described with reference to the accompanying drawings, which, by way of non-limiting examples, represent embodiments and implementations of the apparatus and / or method according to the present invention. The same reference numerals in the drawings represent similar elements or elements having similar functions.

[0058] [ Figure 1 ] is a schematic diagram of the step sequence of a method according to an embodiment of the present invention.

[0059] [ Figure 2 ] is a schematic diagram of the mobile terminal configured to implement the present invention.

[0060] The present invention relates to a method 100, 200 for authenticating a commercial mobile terminal TM, which is intended for use by non-professional customers, such as smartphones, in particular of the smartphone type, the authentication of which is performed by a server S, with the aim of establishing a trusted communication channel between the mobile terminal TM and the server S for executing a payment when specific authentication conditions related to the mobile terminal TM are met.

[0061] The trusted communication channel established when the authentication conditions are met can be, for example, a trusted and secure communication channel, in other words, a communication channel between two mutually authenticated peers whose communications are protected by confidentiality. In particular, this secure communication channel makes it possible to guarantee the authenticity and origin of the key, thereby preventing attacks known as "man-in-the-middle" attacks.

[0062] Refer to the following Figure 1 Describing the steps of the authentication method 100, 200 according to the present invention, consider the following steps implemented by the mobile terminal TM: Figure 1 The vertical line TM in FIG. 1 presents the steps of the method 100 from top to bottom, and the steps along the path implemented by the server S. Figure 1 The steps of the method 200 are presented from top to bottom by the vertical line S in FIG. ; the steps of the method 100 and the method 200 together facilitate authentication of the mobile terminal TM in performing payment.

[0063] The method notably comprises a phase 110, 210 of establishing a trusted communication channel between the mobile terminal TM and the server S, this trusted communication channel being intended to be used during a transaction TR phase 120, 220 of executing a transaction TR related to the execution of a payment using a trusted communication channel CC, CC′ established and / or maintained by the server. When the communication channel is an established trusted communication channel, it will be indicated by the reference CC, and when it is the same established and maintained trusted communication channel, it will be indicated by the reference CC′.

[0064] More specifically, the establishment phase 110, 210 begins with a request step 111, which establishes a communication channel sent by the mobile terminal TM to the server. When the server S receives the request 111 (211), the server S sends an authentication request RA (212) to the mobile terminal TM. The authentication request is randomly selected by the server S from a predefined subset of multiple authentication requests, which define the list of characteristics LC of the mobile terminal TM. Thus, a relatively small number of authentication requests RA are randomly selected from a large number of possible authentication requests. This makes it difficult for a fraudster to design a desired response to the selected authentication request RA by eavesdropping on responses to previous authentication requests.

[0065] The following steps implemented by the mobile terminal TM are a step 112 of receiving an authentication request RA from the server S, followed by a step 113 of collecting the information required for the authentication request RA; this collection results in the creation of a value list LV for the mobile terminal TM, the values ​​in which correspond to the characteristics in the feature list LC of the mobile terminal TM sent by the server S; in other words, each characteristic of the feature list LC can take a certain number of specific values ​​for the mobile terminal TM in question, so that the latter collects specific values ​​corresponding to given characteristics of the feature list LC during the collection step.

[0066] For example, the feature list LC may include at least one of the following features: whether a certain software module exists in the applications installed on the mobile terminal, the brand of the mobile terminal, the identification number of the mobile terminal (for example, the serial number of the mobile terminal), the version of the operating system installed on the mobile terminal, and whether a certain file exists in the file system installed on the mobile terminal. For each of these features, the mobile terminal TM will collect its own specific values ​​to create a value list LV.

[0067] The next step carried out by the mobile terminal TM is that of sending the list of values ​​LV to the server S (114).

[0068] The following steps implemented by the server S are respectively as follows:

[0069] - Receive value list LV (214);

[0070] - determining the security level NS (215) of the mobile terminal TM based on the list of values ​​LV;

[0071] - Establishing a trusted communication channel CC (216) based on the security level NS of the mobile terminal TM.

[0072] Thus, for example, the security level (215) is determined based on one or more of the following characteristic values:

[0073] - the presence or absence of a specific software module in the applications installed on the mobile terminal,

[0074] - the brand of the mobile terminal,

[0075] - the identification number of the mobile terminal,

[0076] - the version of the operating system installed on the mobile terminal,

[0077] - The presence or absence of a specific file in the file system mounted on the mobile terminal.

[0078] For example, the determined security level is compared with a predefined level: if the determined security level is higher than the predefined level, a trusted communication channel CC is established between the server S and the mobile terminal TM (216). Otherwise, the server S does not establish the trusted communication channel CC.

[0079] The trusted communication channel CC established at the end of the step 216 of establishing the trusted communication channel CC may in particular be further protected within the meaning of the above definition.

[0080] Thus, the methods 100 , 200 may in particular use the trusted communication channel CC established ( 216 ) by the server S during the transaction TR phase 120 , 220 , in particular for carrying out the payment procedure.

[0081] According to an exemplary embodiment, the exchanges during the establishment phases 110, 210 can be encrypted to achieve enhanced security; therefore, according to this exemplary embodiment, the server S encrypts the authentication request RA using a variable encryption key selected from a set of encryption keys of the server S (212bis), each encryption key in the set of encryption keys corresponding to a decryption key of the mobile terminal TM, which is recorded in the white box of the mobile terminal TM, and the method 100 also includes a step of decrypting the encrypted authentication request RAC using the decryption key of the mobile terminal TM recorded in the white box of the mobile terminal TM (112bis).

[0082] According to an additional example of embodiment, the method 100 further comprises a step (114bis) of encrypting the list of values ​​LV using another variable encryption key of the mobile terminal TM recorded in the white box of the mobile terminal TM, the encryption step 114bis generating an encrypted list of values ​​LVC, the list of values ​​sent to the server S during the transmission step 114 being the encrypted list of values ​​LVC. Conversely, according to this exemplary embodiment, the method 200 further comprises a step 214bis of decrypting the encrypted list of values ​​LVC by the server S, wherein the another server decryption key S corresponds to the variable encryption key of the mobile terminal TM stored in the white box of the mobile terminal TM, the decryption step 214bis generating the list of values ​​LV.

[0083] Optionally, after the server S establishes 216 the trusted communication channel CC, in particular during the transaction phase 120, 220 TR using the trusted communication channel, the method 100 may further comprise the following steps:

[0084] - receiving one or more further authentication requests ARA (112') from the server S, each further authentication request ARA being randomly selected by the server S from a plurality of authentication requests, each further authentication request defining another list of ALC characteristics of the mobile terminal TM;

[0085] - collecting another value list ALV of the mobile terminal TM (113'), wherein the values ​​in the other value list ALV correspond to the features in the other ALC feature list of the mobile terminal TM;

[0086] - Send the other value list ALV to the server S (114');

[0087] The communication channel CC' is maintained or interrupted by the server S according to the other value ALV list (216').

[0088] Similarly, from the perspective of the server S, the corresponding steps of the method 200 are implemented by the server:

[0089] - sending one or more other authentication requests ARA (212');

[0090] - receiving one or more other lists of values ​​ALV (214'), each other list of values ​​corresponding to one of the other authentication requests ARA;

[0091] - determining a further security level ANS (215') of the mobile terminal TM based on each further list value ALV;

[0092] - Maintaining or interrupting the communication channel CC' according to the further security level ANS.

[0093] Therefore, due to the large number of authentication requests included in the multiple authentication requests, each individual request may involve a small amount of information; therefore, the collection and transmission of this information by the mobile terminal will require limited computing power and load.

[0094] In particular, during the exchange of messages between the mobile terminal TM and the server S using the trusted communication channel CC, the step 212′ of the server sending the other authentication request ARA occurs at a time randomly determined by the server S, so that the step 112′ of the mobile terminal TM receiving this other authentication request ARA occurs at a time according to the time randomly determined by the server S (the time 112′ at which the mobile terminal TM receives this other authentication request is in fact a function of the time 212′ at which the server S sends said other request, which is randomly determined by the server S). The mechanism for issuing one (or more) other authentication requests ARA is therefore “interwoven” with the functional dialogue between the mobile terminal TM and the server S using the trusted communication channel CC, in particular with respect to the phases 120, 220 of implementing the transaction TR.

[0095] According to these provisions, the server randomly selects a limited number of authentication requests from a large number of possible authentication requests, and the server issues these requests at randomly determined times, which makes it more difficult for an attacker to design a mechanism to fraudulently determine the server's expected response.

[0096] According to an additional embodiment example of the methods 100, 200, the trusted communication channel CC is established based on the security level NS of the mobile terminal TM and based on the delay between the reception (214) of the value list LV and the sending (212) of the authentication request; thus, for example, if the reception delay is greater than a predefined delay, or if the security level NS is below a predefined threshold, the server S does not establish the trusted communication channel CC; similarly, the trusted communication channel is maintained or interrupted (216') by the server S based on other security levels ANS of the mobile terminal TM and based on another delay between the reception (214') of other value lists ALV and the sending (212') of other authentication requests ARA among a plurality of other authentication requests that the server S may issue after the establishment of the trusted channel CC, in particular during the phases 120, 220 of the implementation of the transaction TR.

[0097] In the same way that the information exchange can be encrypted during the establishment phases 110, 220, the information exchange after the server S establishes (216) the trusted communication channel CC can also be encrypted before the server S establishes (216) the trusted communication channel CC, with a view to maintaining or interrupting (216') the communication channel CC' of the server S. Thus, according to one embodiment example, the server S encrypts 212'bis the other authentication request ARA using the encryption key of the server S corresponding to the decryption key of the mobile terminal TM, the decryption key being stored in the white box of the mobile terminal TM, and decrypts 112'bis the other encrypted authentication request ARAC using the decryption key of the mobile terminal TM.

[0098] Similarly, method 100 may also include step 114'bis, which uses another variable encryption key of the mobile terminal TM recorded in the white box of the mobile terminal TM to encrypt the other value list ALV, and the encryption step 114'bis produces another encrypted value list ALVC, which is transmitted to the server S during the other transmission 114'; conversely, method 200 also includes a step 214'bis in which the server S uses another server decryption key S corresponding to the variable encryption key of the mobile terminal TM to decrypt the other encrypted value list ALVC, and the decryption step 214bis produces another value list ALV.

[0099] According to one aspect, the present invention relates to a computer program comprising a set of instructions which, when executed on a processor of a mobile terminal TM, are configured to implement a method 100 according to one of the embodiments described above, or, when executed on a processor of a server S, to implement a method 200 according to one of the embodiments described above.

[0100] According to another aspect, the present invention relates to a mobile terminal TM, which includes a processor PC and a memory M and a set of instructions recorded in the memory M, wherein the set of instructions is configured to implement the method 100 according to one of the embodiments described above when the set of instructions is executed on the processor of the mobile terminal TM.

Claims

1. A method (100) for authenticating a mobile terminal (TM) to implement a payment application on the mobile terminal, the mobile terminal (TM) being configured to communicate with a server (S), the method (100) comprising the following steps implemented by the mobile terminal (TM): - receiving (112) an authentication request (RA) from the server (S), the authentication request being randomly selected by the server (S) from a predefined subset of a plurality of authentication requests, the authentication request defining a list of characteristics (LC) of the mobile terminal (TM), - collecting (113) a list of values ​​(LV) of the mobile terminal (TM), the values ​​of which correspond to the characteristics of the list of characteristics (LC) of the mobile terminal (TM) sent by the server (S); - sending (114) said list of values ​​(LV) to said server (S), A trusted communication channel (CC) is established (216) by the server (S) based on the value list (LV) and the security level of the mobile terminal (TM) determined according to the value list (LV).

2. The method (100) according to claim 1, wherein: The established trusted communication channel (CC) is secure.

3. The authentication method (100) according to any one of claims 1 or 2, further comprising the following steps performed after establishing the trusted communication channel (CC): - reception (112') of another authentication request (ARA) from the server (S), the other authentication request (ARA) being randomly selected by the server (S) among a plurality of authentication requests, the other authentication request defining another list of characteristics (ALC) of the mobile terminal (TM); - collection (113') of another list of values ​​(ALV) for said mobile terminal (TM), the values ​​in said other list of values ​​(ALV) corresponding to the features in said other list of features (ALC) of said mobile terminal (TM); - another transmission (114') of said other list of values ​​(ALV) to said server (S); The communication channel (CC) is maintained or interrupted (CC') by the server (S) according to the other list of values ​​(ALV).

4. The method (100) according to the preceding claim, wherein: The time at which the step of receiving (112') another authentication request (ARA) occurs depends on a time randomly determined by the server (S).

5. A method (200) for authenticating a mobile terminal (TM) to implement a payment application on the mobile terminal, the mobile terminal (TM) being configured to communicate with a server (S), the method (200) comprising the following steps implemented by the server (S): - sending (212) an authentication request (RA) to the mobile terminal (TM), the authentication request being randomly selected by the server (S) from a predefined subset of a plurality of authentication requests, the authentication request defining a list of characteristics (LC) of the mobile terminal (TM); - receiving (214) a list of values ​​(LV) whose values ​​correspond to the characteristics of the list of characteristics (LC) of the mobile terminal (TM) sent by the server (S); - determining (215) a security level (NS) of said mobile terminal (TM) based on said list of values ​​(LV); - establishing (216) a trusted communication channel (CC) based on the security level (NS) of said mobile terminal (TM).

6. The method (200) according to claim 5, wherein: The trusted communication channel is established according to the security level (NS) of the mobile terminal (TM) and according to a delay between the reception (214) of the list of values ​​(LV) and the sending (212) of the authentication request.

7. The authentication method (200) according to claim 6, further comprising the following steps performed by the server (S) after establishing the communication channel: - transmission (212') of at least one other authentication request (ARA), said at least one other authentication request being randomly selected by said server (S) from among a plurality of authentication requests; - receiving (214') another list of values ​​(ALV) whose values ​​correspond to features in said feature list (ALC) from said mobile terminal (TM), - a further step of determining (215') another security level (ANS) of said mobile terminal (TM) based on said other list of values ​​(ALV); - Maintaining or interrupting (216') the trusted communication channel (CC') depending on said other security level (ANS).

8. The method (200) of claim 7, wherein: The step of sending (212') at least one other authentication request (ARA) occurs at a time randomly determined by said server (S).

9. The method (200) according to claim 7 or 8, wherein: The communication channel is established according to the other security level (ANS) of the mobile terminal (TM) and according to another delay between the reception (214') of the other list of values ​​(ALV) and the sending (212') of the other authentication request (ARA).

10. A computer program comprising a set of instructions configured to implement the method (100) according to any one of claims 1 to 4 when the instructions are executed on a processor of a mobile terminal (TM), or to implement the method (200) according to any one of claims 5 to 9 when the instructions are executed on a processor of a server (S).

11. A mobile terminal (TM), comprising a processor (PC) and a memory (M) and a set of instructions recorded in the memory (M), wherein the set of instructions is configured to implement the method (100) according to any one of claims 1 to 4 when the instructions are executed on the processor of the mobile terminal (M).

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