Patent Publication Number: US-10791098-B2

Title: Method for providing an authenticated connection between at least two communication partners

Description:
PRIORITY CLAIM 
     This patent application claims priority to German Patent Application No. 10 2016 213 685.2, filed 26 Jul. 2016, the disclosure of which is incorporated herein by reference in its entirety. 
     SUMMARY 
     Illustrative embodiments relate to a method for providing an authenticated connection between at least two communication partners and to a communication system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Disclosed embodiments will be explained with reference to the associated drawings, in which: 
         FIG. 1  shows an exemplary embodiment of the communication system in a schematic illustration; and 
         FIG. 2  shows an exemplary embodiment of the method in a schematic flow diagram. 
     
    
    
     DETAILED DESCRIPTION 
     Modern vehicles have infotainment systems which can be coupled to smartphones. By virtue of the coupling, an infotainment system can access media contents, for example, which are stored on the coupled smartphone, to reproduce them in the vehicle. 
     Moreover, a signal-conducting connection between the vehicle-internal infotainment system and the smartphone can be used to carry out a user identification or to provide application-related user data for the infotainment system. 
     Since personal data and application-related access data are usually also communicated between the infotainment system and the smartphone, the signal-conducting connection should be equipped with suitable protection. 
     The document DE 10 2005 023 544 A1 proposes for this purpose a communication system comprising a vehicle operating unit, a vehicle output unit, an interface computer and a mobile terminal, wherein the interface computer has access protection so that the mobile terminal can only access authorized vehicle functions. 
     The document DE 10 2012 008 834 A1 additionally discloses a method for connecting terminals to a device inherent to the vehicle, wherein coupling information is generated for connections between a terminal and a first pairing server, the coupling information being transmitted to a second pairing server to carry out a check of the authorization of the terminal. 
     Furthermore, the document DE 10 2014 118 555 A1 proposes a method for connecting a wireless terminal to a vehicle, wherein, after establishing a connection and identifying the wireless terminal, the method firstly determines whether the wireless terminal is authenticated and thus suitable for a connection to an infotainment system before a data exchange takes place. 
     In the known solutions, the authentication is always effected at the communication channel level. By way of example, the authentication of a BLUETOOTH® connection takes place, which can be used for all applications after successful authentication. 
     There is the problem, however, that it is not always the intention for all applications to have access to an authenticated connection. However, the known solutions are not suitable for authentication at the application level. 
     Disclosed embodiments enable a secure and convenient authentication of a connection between two communication partners, wherein the authentication can also be effected at the application level. 
     In the disclosed method for providing an authenticated connection between at least two communication partners, a shared secret key for the at least two communication partners is provided before an anonymous signal-conducting connection is set up between the at least two communication partners. All messages of the connection between the at least two communication partners are encrypted using the shared secret key. The connection between the at least two communication partners is authenticated by a user in addition to the encryption of the messages using the shared secret key. 
     The disclosed method provides a symmetrical or hybrid crypto-system in which the at least two communication partners use the same key for encryption and a preceding key exchange thus need not take place is combined with a pairing method in which the user additionally authenticates the connection between the at least two communication partners. The additional authentication, which is to be performed by the user, makes it possible to effectively avoid a man-in-the-middle attack (MITM attack). The security of the connection between the at least two communication partners is thus increased. Moreover, the necessity of user action allows the implementation of the authentication at the application level. 
     In the method, a first communication partner of the at least two communication partners can be embodied as a vehicle-internal device. The vehicle-internal device is embodied as an infotainment system of the vehicle. The first communication partner of the at least two communication partners may act as a server. Alternatively or additionally, in the method, a second communication partner of the at least two communication partners can be embodied as a mobile terminal. The mobile terminal is embodied as a smartphone. The second communication partner of the at least two communication partners may act as a client. 
     The anonymous signal-conducting connection between the at least two communication partners can be based on a transport layer security protocol. As a result of the hybrid encryption of the transport layer security protocol, security is increased further without the necessity of a preceding key exchange. The transport layer security protocol makes it possible to implement higher protocols on the basis of the transport layer security protocol protocol. The transport layer security protocol is thus independent of applications and of the system used. 
     Providing a shared secret key for the at least two communication partners can comprise carrying out a key exchange protocol for generating the shared secret key. The key exchange protocol may be an asymmetrical key exchange protocol, by means of which the shared secret key generated can be securely transmitted even via an intercepted communication channel. It is thus not necessary that the shared secret key must be communicated via a secure communication channel. Connection set-up is thus simplified and accelerated. 
     The key exchange protocol can comprise a Diffie-Hellman key exchange protocol. The Diffie-Hellman key exchange protocol used is based on elliptic curves (Elliptic Curve Diffie-Hellman (ECDH)). By means of the Diffie-Hellman key exchange protocol, the at least two communication partners can generate a shared secret key via a public and non-protected communication channel. In the case of the Diffie-Hellman key exchange protocol, however, there is the risk of an attacker intruding between the at least two communication partners and thus being able to alter messages. Since, in the disclosed method, a subsequent authentication of the connection is effected by the user, this risk is eliminated, with the result that the use of the Diffie-Hellman key exchange protocol for generating a shared secret key is suitable in the disclosed method. 
     Authenticating the connection between the at least two communication partners by the user can comprise calculating an integrity check value on the basis of the shared secret key by a first communication partner of the at least two communication partners, and/or calculating an integrity check value on the basis of the shared secret key by a second communication partner of the at least two communication partners. The calculation of an integrity check value makes it possible to check whether a man-in-the-middle attack has taken place. The integrity check value makes it possible to ensure that no undesired modification that could not be prevented has taken place. For this purpose, authenticating the connection between the at least two communication partners by the user may comprise reproducing, by the first communication partner, the integrity check value calculated by the first communication partner, and/or reproducing, by the second communication partner, the integrity check value calculated by the second communication partner. Reproducing the integrity check value calculated by the first communication partner can be effected, for example, by an optical reproduction of the integrity check value by means of a display unit of the first communication partner and/or by an acoustic reproduction of the integrity check value by means of a sound reproduction device of the first communication partner. Reproducing the integrity check value calculated by the second communication partner can be effected, for example, by an optical reproduction of the integrity check value by means of a display unit of the second communication partner and/or by an acoustic reproduction of the integrity check value by means of a sound reproduction device of the second communication partner. 
     Authenticating the connection between the at least two communication partners by the user can comprise comparing, by the user, the integrity check value reproduced by the first communication partner with the integrity check value reproduced by the second communication partner, and/or confirming, by the user, the equality of the integrity check value reproduced by the first communication partner and the integrity check value reproduced by the second communication partner. Confirming, by the user, the equality of the integrity check value reproduced by the first communication partner and the integrity check value reproduced by the second communication partner concludes the integrity check. If the integrity check values reproduced by the first communication partner and the second communication partner correspond, then the situation that an unnoticed man-in-the-middle attack has taken place can be ruled out. Authenticating the connection between the at least two communication partners can thus be effected by the user by the confirmation of the equality of the integrity check value reproduced by the first communication partner and the integrity check value reproduced by the second communication partner. In the case of a man-in-the-middle attack having been carried out, the integrity check value reproduced by the first communication partner would deviate from the integrity check value reproduced by the second communication partner. In this case, by means of a corresponding input, the user can notify the first communication partner and/or the second communication partner that correspondence is not present. The authentication would thus have failed since it must be assumed that a man-in-the-middle attack has taken place. 
     Confirming, by the user, the equality of the integrity check value reproduced by the first communication partner and the integrity check value reproduced by the second communication partner can comprise actuating an actuation device of the first communication partner by the user, and/or actuating an actuation device of the second communication partner by the user. The actuation device of the first communication partner and/or the actuation device of the second communication partner may comprise in each case one or more pressure-sensitive input elements, such as, for example, pushbuttons or keys, and/or a touchscreen. Alternatively or additionally, the actuation device of the first communication partner and/or the actuation device of the second communication partner comprise(s) in each case a sound recording device and an evaluation unit which is connected to the sound recording device and which is designed to evaluate voice inputs of the user. 
     The integrity check value calculated by the first communication partner and/or the second communication partner can be a checksum over the shared secret key or a checksum over a value derived from the shared secret key. The first communication partner and/or the second communication partner may calculate the integrity check value in each case by means of a cryptological hash function. The value determined therefrom does not permit the shared secret key to be inferred and is thus suitable for the disclosed method. 
     The disclosed communication system comprises at least two communication partners, wherein the at least two communication partners are configured to set up an anonymous signal-conducting connection to one another. In this case, all messages of the connection between the at least two communication partners are encrypted using a shared secret key. The at least two communication partners are additionally configured to the effect that a user can authenticate the connection between the at least two communication partners. 
     The disclosed communication system provides a symmetrical or hybrid crypto-system in which the at least two communication partners use the same key for encryption and a preceding key exchange thus need not take place is combined with a pairing method in which the user additionally authenticates the connection between the at least two communication partners. The additional authentication, which is to be performed by the user, makes it possible to effectively avoid a man-in-the-middle attack. The security of the connection between the at least two communication partners is thus increased. Moreover, the necessity of user action allows the implementation of the authentication at the application level. 
     A first communication partner of the at least two communication partners of the communication system can be embodied as a vehicle-internal device. The vehicle-internal device is embodied as an infotainment system of the vehicle. The first communication partner of the at least two communication partners may act as a server. Alternatively or additionally, a second communication partner of the at least two communication partners of the communication system is embodied as a mobile terminal. The mobile terminal is embodied as a smartphone. The second communication partner of the at least two communication partners may act as a client. 
     In the communication system, the anonymous signal-conducting connection between the at least two communication partners can be based on a transport layer security protocol. As a result of the hybrid encryption of the transport layer security protocol, security is increased further without the necessity of a preceding key exchange. The transport layer security protocol makes it possible to implement higher protocols on the basis of the transport layer security protocol protocol. The transport layer security protocol is thus independent of applications and of the system used. 
     The at least two communication partners can be configured to implement a key exchange protocol, in particular, a Diffie-Hellman key exchange protocol, for generating the shared secret key. The at least two communication partners are configured to implement a Diffie-Hellman key exchange protocol based on elliptic curves (Elliptic Curve Diffie-Hellman (ECDH)). By means of the Diffie-Hellman key exchange protocol, the at least two communication partners can generate a shared secret key via a public and non-protected communication channel. In the case of the Diffie-Hellman key exchange protocol, however, there is the risk of an attacker intruding between the at least two communication partners and thus being able to alter messages. Since, in the disclosed communication system, a subsequent authentication of the connection can be effected by the user, this risk is eliminated, with the result that the use of the Diffie-Hellman key exchange protocol for generating a shared secret key is suitable in the disclosed communication system. 
     The at least two communication partners can be configured in each case to calculate an integrity check value on the basis of the shared secret key and to reproduce it for the user by means of a display device, wherein the at least two communication partners may provide for the user in each case an actuation device for confirming the equality of the integrity check values reproduced by the at least two communication partners. The calculation of an integrity check value makes it possible to check whether a man-in-the-middle attack has taken place. The integrity check value makes it possible to ensure that no undesired modification that could not be prevented has taken place. The display device can be configured to reproduce the integrity check value optically and/or acoustically. 
     The communication system can additionally be configured to perform the method for providing an authenticated connection between at least two communication partners according to at least one of the embodiments described above. The same benefits and modifications as described above are applicable. 
     Further configurations are evident from the rest of the features mentioned herein. 
     The various disclosed embodiments mentioned in this application, unless explained otherwise in an individual case, can be combined with one another. 
       FIG. 1  shows a communication system  10  comprising two communication partners  12 ,  14 . The first communication partner  12  is embodied as a vehicle-internal device of the vehicle  34 , wherein the vehicle-internal device is an infotainment system. The second communication partner  14  is embodied as a mobile terminal, wherein the mobile terminal is embodied as a smartphone. 
     The first communication partner  12  comprises a computing unit  18 , a communication module  20 , a display device  22  and an actuation device  24 . The communication module  20 , the display device  22  and the actuation device  24  are connected to the computing unit  18  in a signal-conducting manner. The communication module  20  is configured to communicate with other communication partners wirelessly, for example, by BLUETOOTH®. The display device  22  is embodied as a display and integrated into the dashboard of the vehicle  34 . The actuation device  24  comprises a plurality of pressure-sensitive input elements and is integrated into the center console of the vehicle  34 . 
     The second communication partner  14  likewise comprises a computing unit  26 , a communication module  28 , a display device  30  and an actuation device  32 . The communication module  28 , the display device  30  and the actuation device  32  are connected to the computing unit  26  in a signal-conducting manner. The communication module  28  is configured to communicate with other communication partners wirelessly, for example, by BLUETOOTH®. The display device  30  is embodied as a touchscreen. The actuation device  32  is embodied as a pushbutton. 
     The two communication partners  12 ,  14  are configured to set up an anonymous signal-conducting connection  16  to one another via the respective communication modules  20 ,  28 , wherein all messages of the connection  16  between the two communication partners  12 ,  14  are encrypted using a shared secret key. By virtue of the fact that the two communication partners  12 ,  14  are configured to implement a Diffie-Hellman key exchange protocol for generating the shared secret key, the key generation can be effected via a public and non-protected communication channel. The anonymous signal-conducting connection  16  between the two communication partners  12 ,  14  is based on a transport layer security protocol. 
     The two communication partners  12 ,  14  are configured to the effect that a user can authenticate the connection  16  between the two communication partners  12 ,  14 . For this purpose, the first communication partner  12  and the second communication partner  14  calculate in each case an integrity check value on the basis of the shared secret key and display the calculated integrity check value to the user by means of the respective display device  22 ,  30 . Via the respective actuation devices  24 ,  32 , the user can then confirm the equality of the integrity check values displayed by the two communication partners  12 ,  14 . 
     Authenticating the connection  16  between the two communication partners  12 ,  14  is effected by the user by the confirmation of the equality of the integrity check value displayed by the first communication partner  12  and the integrity check value reproduced by the second communication partner  14 . 
     The communication system  10  shown is configured to perform the method for providing an authenticated connection  16  between at least two communication partners  12 ,  14 . 
       FIG. 2  shows the disclosed method for providing an authenticated connection  16  between two communication partners  12 ,  14 , which begins with the following operation:
           36 ) providing a shared secret key for the two communication partners  12 ,  14 .       

     In this case, the first communication partner  12  is embodied as a vehicle-internal infotainment system and the second communication partner  14  is embodied as a smartphone. 
     Providing a shared secret key for the two communication partners  12 ,  14  comprises the following operation:
           38 ) carrying out a key exchange protocol for generating the shared secret key.       

     The key exchange protocol carried out is a Diffie-Hellman key exchange protocol. After a shared secret key has been provided for the two communication partners  12 ,  14 , the following operation can be performed:
           40 ) setting up an anonymous signal-conducting connection  16  between the two communication partners  12 ,  14 , wherein all messages of the connection  16  between the two communication partners  12 ,  14  are encrypted using the shared secret key.       

     The set-up anonymous signal-conducting connection  16  between the two communication partners  12 ,  14  is based on a transport layer security protocol. After the anonymous signal-conducting connection  16  between the two communication partners  12 ,  14  has been set up, the following operation is performed:
           42 ) authenticating the connection  16  between the two communication partners  12 ,  14  by a user.       

     Authenticating the connection  16  between the two communication partners  12 ,  14  by the user comprises the following operations:
           44 ) calculating an integrity check value on the basis of the shared secret key by a first communication partner  12  of the two communication partners  12 ,  14 ; and     46 ) reproducing, by the first communication partner  12 , the integrity check value calculated by the first communication partner  12 .       

     Moreover, authenticating the connection  16  between the two communication partners  12 ,  14  by the user comprises the following operations:
           48 ) calculating an integrity check value on the basis of the shared secret key by a second communication partner  14  of the two communication partners  12 ,  14 ; and     50 ) reproducing, by the second communication partner  14 , the integrity check value calculated by the second communication partner  14 .       

     The integrity check value calculated by the first communication partner  12  and the second communication partner  14  is a checksum over the shared secret key. After the calculated integrity check value has in each case been reproduced for the user by the first communication partner  12  and the second communication partner  14 , the following operation can be performed:
           52 ) comparing, by the user, the integrity check value reproduced by the first communication partner  12  with the integrity check value reproduced by the second communication partner  14 .       

     After the equality of the integrity check value reproduced by the first communication partner  12  with the integrity check value reproduced by the second communication partner  14  has been ascertained by the user, the following operation can be performed:
           54 ) confirming, by the user, the equality of the integrity check value reproduced by the first communication partner  12  and the integrity check value reproduced by the second communication partner  14 .       

     Confirming, by the user, the equality of the integrity check value reproduced by the first communication partner  12  and the integrity check value reproduced by the second communication partner  14  comprises the following operations:
           56 ) actuating an actuation device  24  of the first communication partner  12  by the user; and     58 ) actuating an actuation device  32  of the second communication partner  14  by the user.       

     Authenticating the connection  16  between the two communication partners  12 ,  14  is effected by the user by the confirmation of the equality of the integrity check value reproduced by the first communication partner  12  and the integrity check value reproduced by the second communication partner  14 . 
     The disclosed embodiments enable a secure and convenient authentication of a connection between two communication partners, without having to resort to a public key infrastructure. The authentication of the connection is effected via a public and non-protected communication channel and can also be effected at the application level. 
     LIST OF REFERENCE SIGNS 
       10  Communication System 
       12  First communication partner 
       14  Second communication partner 
       16  Connection 
       18  Computing unit 
       20  Communication module 
       22  Display device 
       24  Actuation device 
       26  Computing unit 
       28  Communication module 
       30  Display device 
       32  Actuation device 
       34  Vehicle 
       36 - 58  Method operations