METHOD FOR AUTHORIZING A CENTRAL UNIT CONNECTED TO PERIPHERAL UNITS USING A SECURE SERVER

Abstract

Method for authenticating the rights of a central unit (2) communicating with peripheral units (6) performing measurements to carry out sensitive operations on them, using an external secure server (12) possessing their identifiers (4, 8), each peripheral unit (6) generating a random session code (n) transmitted to the server with its identifier, the identifier of the peripheral unit and the session code, the server performs encryption with a dynamic encryption key (10) shared with the peripheral unit (6) to form a first dynamic encryption key (28), then performs a second encryption with the identifier of the central unit (4) to give encrypted information from the central unit (32) transmitted to the peripheral unit (6) which performs the same encryption to form a second provisional encryption key (38), then a reverse decryption giving a decrypted identifier (42),then compares this decrypted identifier with the identifier of the central processing unit (4) to grant it authentication. Figure for the abbreviation: Figure 1,

Description

Title of the invention: METHOD FOR AUTHENTICATING A CENTRAL UNIT CONNECTED TO PERIPHERAL UNITS USING A SECURE SERVER Technical field

[0001] The present invention relates to a method for authenticating the rights of a central unit to communicate with peripheral units using a secure server connected by an Internet link, in order to carry out sensitive operations on these peripheral units, as well as units and a motor vehicle comprising devices implementing this method. Prior art

[0002] A type of method of communication between a system for monitoring the pressure of the tires of a motor vehicle, called "Tire pressure monitoring Systems" in English, "TMPS" for short, and intelligent equipment of a user of this vehicle, presented in particular by the document FR-A1-3084310, comprises a peripheral unit installed on each wheel of the vehicle measuring parameters such as the inflation pressure and the temperature of the tire, which are transmitted by radio frequency, in particular using the "Bluetooth" standard, to a central unit arranged in the vehicle receiving the information to process it and inform the driver or a repairer in order to alert in the event of a problem detected.

[0003] In particular, the wheel units periodically transmit information to the central unit, using a unique identifier of its own making it possible to identify the wheel concerned. Each wheel unit also has a wave receiver receiving signals from the central unit, to carry out diagnostic, configuration or learning operations of this wheel unit.

[0004] The method presents the use of ultra high frequency "UHF" waves, exceeding the gigahertz, making it possible to offer new applications such as exchange with equipment external to the vehicle, in particular a user's smartphone, called "Smartphone" in English.

[0005] Furthermore, generally speaking, in the case of a system carrying out radiofrequency exchanges between a central unit of a user or client, and peripheral units recording data, for example for these tire pressure monitoring systems, it may be necessary to carry out sensitive operations on these peripheral units, such as their reprogramming, using the Internet network and computer services managed by a remote server, called "cloud computing" in English.

[0006] Each unit has as an identifier a specific address stored in a physical memory for controlling access to the medium, called "Media Access Control" in English, "MAC" for short. The authentication of the user's central unit by the peripheral units to carry out sensitive operations on it such as reprogramming, poses problems for, in a simple manner, without loading the server with exchanges of large volumes of data, ensuring a high level of security in order to avoid unwanted interventions by third parties such as hacking, and confidentiality of data exchanges.

[0007] The present invention aims in particular to avoid these problems of the prior art. Statement of the invention

[0008] To this end, it proposes a method for authenticating the rights of a central unit of a user communicating bidirectionally with one or more peripheral units carrying out measurements transmitted to this central unit, to carry out sensitive operations thereon, each central and peripheral unit having a specific identifier, this method using via the Internet network a secure external server which has in a database the identifier of the peripheral units, and a symmetric encryption key which is shared with each peripheral unit, this method being remarkable in that it comprises the following successive steps: - in a first step the central unit uses its identifier and a password to be recognized by each peripheral unit, in parallel the central unit establishes a secure connection with the server by authenticating itself so that it recognizes in its database the identifier of the peripheral unit concerned; - in a second step the peripheral unit generates a new random session code and notifies it to the central unit; - in a third step the central unit transmits to the server its identifier, the identifier of the peripheral unit and the session code to request proof of its authentication in order to obtain administration rights on this peripheral unit; - the server performs in a fourth step a first encryption with the shared encryption key recognized by its identifier, and with the session code to form a first shared and random dynamic provisional encryption key, then performs in a fifth step a second encryption with the identifier of the central unit and this first dynamic provisional encryption key to provide encrypted central unit information as proof of authentication; - in a sixth step the encrypted information of central unit is transmitted to the unit central unit, then in a seventh step the central unit in turn transmits it to the peripheral unit; - the peripheral unit performs in parallel in an eighth step the same first encryption as that performed by the server in its fourth step with its shared encryption key and its session code, to form a second provisional encryption key, then it performs in a ninth step a reverse decryption of the second encryption of the fifth step, with the second provisional encryption key and the encrypted information giving a decrypted identifier; and finally - in a tenth step the peripheral unit compares the decrypted identifier with the identifier of the central unit to grant this central unit its authentication if they coincide.

[0009] An advantage of the authentication method according to the invention is that it makes it possible to simplify the procedure for encrypting the source files stored in the server in order to avoid overloading this server, the encrypted files being created only once for all the peripheral units.

[0010] The rights authentication method according to the invention may further comprise one or more of the following characteristics, which may be combined with each other.

[0011] Advantageously, in a following step the secure server generating and hosting a special dynamic encryption key, uses it to encrypt a software source file giving an encrypted file, then in a following step the server uses the first dynamic shared encryption key to encrypt the special encryption key by giving a new encrypted key, then in a following step the server delivers to the central unit the encrypted file and the new encrypted key, this central unit delivering them in turn in a following step to the peripheral unit.

[0012] In this case, advantageously in a following step the peripheral unit uses the new encrypted key and the first dynamic provisional encryption key to form the same special encryption key as that held by the server, then in a following step the peripheral unit uses the special encryption key to decrypt the encrypted file with an operation inverse to the encryption operation previously carried out by the server, in order to deliver the source file.

[0013] Advantageously, the source file is then verified with a checksum before being programmed into the memory of the peripheral unit.

[0014] Advantageously, the secure connection with the server uses a secure hypertext transfer protocol “HTTPS”.

[0015] Advantageously, once the secure connection with the server is established, the server checks in its database whether the central unit is authorized to communicate with the peripheral units.

[0016] Advantageously, during the same open communication session with the unit device, the central unit sends it the encrypted information again as proof of authentication without using the server.

[0017] The invention also relates to a system comprising a central unit, and peripheral units carrying out measurements, connected to each other by radio frequency, comprising devices implementing a method comprising any one of the preceding characteristics.

[0018] The invention further relates to a motor vehicle comprising a central unit, and peripheral units carrying out measurements on the tires of the wheels of this vehicle, comprising devices implementing a method comprising any one of the preceding characteristics. Brief description of the drawings

[0019] [Fig-1] is a functional diagram showing the method according to the invention authentication of a central unit located in a motor vehicle, connected to peripheral units fixed to the wheels of the vehicle; and

[0020] [Fig.2] is a functional diagram showing after this authentication the repro programming of peripheral units. Description of the embodiments

[0021] [Fig.l] shows in a motor vehicle a central unit 2 forming a client having a central unit identifier 4, and on each wheel a peripheral unit 6 comprising pressure and temperature sensors of the tire of the wheel, having a peripheral unit identifier 8 and a specific shared symmetric encryption key 10, recorded during the manufacture of this unit. The central unit 2 and the peripheral units 6 communicate with each other using in particular the “Bluetooth®” standard.

[0022] An Internet network 14 using a radio frequency link makes it possible to connect the central unit 2 to an external secure server 12 containing a database comprising for each peripheral unit 6 its identifier 8 and its shared encryption key 10.

[0023] The authentication method of the central unit 2 allowing sensitive operations to be carried out on the peripheral units 6, comprises a first step 20 of using the identifier of the central unit 4 and a password to be recognized by a specific peripheral unit 6, and to accept the connection.

[0024] In parallel, the central unit 2 is connected by a secure link 14 to the server 12 so that it recognizes in its database the identifier of the specific unit concerned 6. Advantageously, a link by secure hypertext transfer protocol, called "HyperText Transfer Protocol Secure" in English, "HTTPS" for short, is used, taking for example the identifier of the central unit 4 and a password.

[0025] In a second step 22 the peripheral unit 6 generates a new session code, which may in particular be a random session number (n), and notifies it to the central unit 2.

[0026] In a third step 24, the central unit 2 transmits to the server 12 its identifier 4, the identifier 8 of the peripheral unit 6 and the session number (n), to request proof of its authentication in order to obtain administration rights on this peripheral unit. The server 12 then checks in its database whether the central unit 2 is authorized to communicate with this peripheral unit 6, using their respective identifiers 4, 8.

[0027] If the central unit 2 is authorized to communicate with the peripheral unit 6, in a fourth step 26 the server 12 performs a first encryption with the shared encryption key 10 recognized by its identifier 8, and with the session number (n) to form a first shared and random dynamic provisional encryption key 28.

[0028] The server 12 then performs in a fifth step 30 a second encryption with the identifier of the central unit 4 and this first dynamic provisional encryption key 28 in order to produce encrypted central server information forming proof of authentication 32.

[0029] In a sixth step 34 the server 12 transmits to the central unit 2 the encrypted authentication proof information 32. In a seventh step 36 the central unit 2 in turn transmits to the particular unit 6 the encrypted authentication proof information 32.

[0030] In parallel with the operations carried out by the secure server 12, in an eighth step 50 the peripheral unit 6 carries out the same fourth step of first encryption 26 carried out by the server 12, using its shared encryption key 10 and its session number (n) to form a second provisional encryption key 38. The peripheral unit 6 then carries out in a ninth step 40 a reverse decryption of the fifth step 30 of the second encryption, with the second provisional encryption key 38 and the encrypted authentication proof information 32, giving a decrypted identifier 42.

[0031] In a final tenth step 44 the peripheral unit 6 compares the decrypted identifier 42 with the identifier of the central unit 4, if they coincide it then grants this central unit its authentication. In this way, validation by the remote secure server 12 of the authentication of the central unit 2 is obtained, which is then authorized to carry out sensitive operations on the peripheral unit 6 such as its reprogramming with a high level of security and confidentiality.

[0032] With this method the central unit 2 can subsequently give this proof again to the peripheral unit 6 without the help of the server 12, but only during the same communication session with this peripheral unit. In this way, an outsider wanting to hack the system by trying to connect during the next session, will not be able to provide this proof and will not be able to pretend to be the client.

[0033] [Fig.2] shows the secure server 12 generating and hosting a special dynamic encryption key 60 which is used to, in an encryption operation 66, encrypt a software source file 62 by giving an encrypted file 64 which is to be loaded into the peripheral unit 6. In all cases the server 12 keeps an identical image of the file present in the peripheral unit 6. In particular the special dynamic encryption key 60 can be unique by being used to encrypt a single source file 62, or can be used for the encryption of all the files.

[0034] After the previous authentication sequence of the central unit 2, the central unit 2 has obtained the administrator function, the first dynamic temporary encryption key 28 is shared between the server 12 and the peripheral unit 6.

[0035] In a following step 70 the server 12 uses the first shared dynamic temporary encryption key 28 to encrypt the special encryption key 60, giving a new encrypted key 72 which can be shared with the peripheral unit 6.

[0036] In a following step 78 the server 12 delivers to the central unit 2 the encrypted file 64 and the new encrypted key 72, this central unit delivering them in turn in a following step 80 to the peripheral unit 6.

[0037] In a following step 84 the peripheral unit 6 uses the new encrypted key 72 and the new shared dynamic encryption key 28, to form the same special encryption key 60 as that held by the server 12. And finally in a following step 86 the peripheral unit 6 uses the special encryption key 60 to decrypt the encrypted file 64 with an inverse operation of the encryption operation 66 previously carried out by the server 12, in order to deliver the source file 62. The source file 62 is then verified with a checksum, then it is programmed into the memory of the peripheral unit 6 to be used.

[0038] The method according to the invention has the principle of always using the same special encryption key 60 to encode the files 62, which avoids the systematic encoding phase. The special encryption key 60 being unknown to the peripheral units 6, the new encrypted key 72 is transmitted encrypted thanks to the shared dynamic encryption key 28 advantageously created during the authentication phase.

[0039] Decryption of the encrypted key 72 is not possible on the central unit 2, a hacker not possessing the shared dynamic temporary encryption key 28 created after authentication. This method remains secure as long as the special key of 60 encryption is not known by hackers.

[0040] Advantageously, the encryptions and decryptions are carried out with the “AES128” standard, for “Advanced Encryption Standard” in English, or advanced encryption standard.

[0041] The authentication method according to the invention is particularly suitable for checking the tires of a motor vehicle, in order to notify the user or a repairer of failures or to prevent them. It also allows car manufacturers or tire manufacturers to receive information on an external server to ensure monitoring of their products and to improve quality.

Claims

Claims

1. Method for authenticating the rights of a central unit (2) of a user communicating bidirectionally with one or more peripheral units (6) carrying out measurements on the tires of the wheels of a motor vehicle, transmitted to this central unit (2), to carry out sensitive operations thereon, each central unit (2) and peripheral unit (6) having a specific identifier (4, 8), this method using via the Internet network (14) a secure external server (12) which has in a database the identifier (8) of the peripheral units (6), and a symmetric encryption key (10) which is shared with each peripheral unit (6), characterized in that it comprises the following successive steps: - in a first step (20) the central unit (2) uses its identifier (4) and a password to be recognized by each peripheral unit (6), in parallel the central unit (2) establishes a secure link (14) with the server (12) by authenticating itself so that it recognizes in its database the identifier (8) of the peripheral unit concerned (6) - in a second step (22) the peripheral unit (6) generates a new random session code (n) and notifies it to the central unit (2); - in a third step (24) the central unit (2) transmits to the server (12) its identifier (4), the identifier (8) of the peripheral unit (6) and the session code (n) to request proof of its authentication in order to obtain administration rights on this peripheral unit (6); - the server performs in a fourth step (26) a first encryption with the shared encryption key (10) recognized by its identifier (8), and with the session code (n) to form a first shared and random dynamic temporary encryption key (28), then performs in a fifth step (30) a second encryption with the identifier of the central unit (4) and this first dynamic temporary encryption key (28) to give encrypted central unit information as proof of authentication (32); - in a sixth step (34) the encrypted information (32) is transmitted to the central unit (2), then in a seventh step (36) the central unit (2) transmits it in turn to the peripheral unit (6); - the peripheral unit (6) performs in parallel in an eighth step (50) the same first encryption as that carried out by the server (12) in its fourth step (26), with its shared encryption key (10) and its session code (n), to form a second provisional encryption key (38), then it carries out in a ninth step (40) a reverse decryption of the second encryption of the fifth step (30), with the second provisional encryption key (38) and the encrypted information (32) giving a decrypted identifier (42); and finally - in a tenth step (44) the peripheral unit (6) compares the decrypted identifier (42) with the identifier of the central unit (4) to if they coincide grant this central unit (2) its authentication.

2. Method according to claim 1, characterized in that in a following step (66) the secure server (12) generating and hosting a special dynamic encryption key (60), uses it to encrypt a software source file (62) giving an encrypted file (64), then in a following step (70) the server (12) uses the first dynamic temporary encryption key (28) to encrypt the special encryption key (60) by giving a new encrypted key (72), then in a following step (78) the server (12) delivers to the central unit (2) the encrypted file (64) and the new encrypted key (72), this central unit (12) delivering them in turn in a following step (80) to the peripheral unit (6).

3. Method according to claim 2, characterized in that in a following step (84) the peripheral unit (6) uses the new encrypted key (72) and the new shared dynamic encryption key (28) to form the same special encryption key (60) as that held by the server (12), then in a following step (86) the peripheral unit (6) uses the special encryption key (60) to decrypt the encrypted file (64) with an operation inverse to the encryption operation (66) previously carried out by the server (12), in order to deliver the source file (62).

4. Method according to claim 3, characterized in that the source file (62) is then verified with a checksum before being programmed into the memory of the peripheral unit (6).

5. Method according to any one of the preceding claims, characterized in that the secure connection (14) with the server (12) uses a secure hypertext transfer protocol “HTTPS”.

6. Method according to any one of the preceding claims, characterized in that once the secure connection (14) with the server (12) has been established, the server checks in its database whether the central unit (2) is authorized to communicate with peripheral units (6).

7. Method according to any one of the preceding claims, characterized in that during the same communication session opened with the peripheral unit (6), the central unit (2) sends it again the encrypted information (32) as proof of authentication without using the server (12).

8. System comprising a central unit (2), and peripheral units (6) carrying out measurements on the tires of the wheels of a motor vehicle, connected by radio frequency to each other, characterized in that it comprises devices implementing a method according to any one of the preceding claims.

9. Motor vehicle comprising a central unit (2), and peripheral units (6) carrying out measurements on the tires of the wheels of this vehicle, characterized in that it comprises devices implementing a method according to any one of claims 1 to 7.

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