WO2003003655A1

WO2003003655A1 - Method for secure radio-frequency communication

Info

Publication number: WO2003003655A1
Application number: PCT/FR2002/002142
Authority: WO
Inventors: Ludovic Rousseau; Christophe Arnoux; Cédric CARDONNEL
Original assignee: Gemplus
Priority date: 2001-06-20
Filing date: 2002-06-20
Publication date: 2003-01-09
Also published as: FR2826536A1; FR2826536B1

Abstract

The invention relates to a method for secure radio-frequency communication between several devices or units in a communication network, characterised in comprising the following steps:- transmitting a communication request (70), for a device (46), to a communication network control unit (40) and replying to said communication request (72 to 84) as a function of determined criteria. The user (44) of the control unit (40) defines at least one of the determined criteria. The invention is applicable to radio frequency networks such as defined by the 'BLUETOOTH' standard.

Description

SECURE RADIO FREQUENCY COMMUNICATION METHOD

The invention relates to radio frequency communication networks, and more particularly in such networks, a method for securing communications s between the various devices or devices capable of being connected to each other. It targets in particular private networks in which several radiofrequency communication devices, distant from a few tens or hundreds of meters, 0 for example located in the same building, are capable of communicating with one another.

It is particularly suitable for devices using communication technologies, defined by the so-called "BLUETOOTH" standard (defined in the 5 documents ETS 300-328 and ETS 300-339) and by the 802.11 standard.

Today, secure communications between such devices are encrypted using a secret communication key 0, which guarantees confidentiality, integrity and authentication between the devices. There is a communication key per pair of devices, which is established when the two devices are connected for the first time by a so-called pairing procedure.

In the case of a network according to the BLUETOOTH standard, a “subset of devices” which at a given instant communicate with each other is called “PICONET”. It should be noted that clear communication, and therefore not secure 0, remains possible with any device outside the piconet.

This request relates to secure communications; in this context, before a communication with an external device to the "PICONET", a procedure to assign communication keys is necessary. This procedure poses security problems, which are resolved in particular according to a solution proposed in French patent application n ° 00-09774 filed by the applicant.

However, before exchanging cryptographic communication keys during a pairing procedure, no control is provided to determine whether the device which requires its connection to the piconet fulfills certain conditions in order to exchange messages with all the piconet devices or only with some of them. Each external device can connect to the piconet independently and without effective control. As a result, a malicious intruder can connect to a Piconet and carry out fraudulent operations there, such as "theft" of the cryptographic keys which are used between two devices, in order to decrypt the messages exchanged, or access to personal and confidential data without the knowledge of the person concerned.

The object of the present invention is therefore to implement a method of secure radio frequency communication between a plurality of devices in a communication network. The invention therefore relates to a method of radiofrequency communication between a plurality of devices or apparatuses of a communication network, characterized in that it comprises the following steps consisting in:

(a) send a communication request to a communication network control device, and

(b) respond to this communication request according to determined criteria. The user of the communication network control device defines at least one of the determined criteria.

The communication network control device generates a negative response message when one of the determined criteria is not fulfilled.

The communication network control device generates at least a first positive response message to said communication request when the determined criteria are fulfilled, said first positive response message comprising at least one session key to allow a first network device communication system to communicate with a second device of the communication network. The communication network control device generates a second positive response message which is transmitted to a second communication network device with which the first device wishes to communicate, said second message comprising said session key which is used for communication between the first device and the second device. The first and second positive response messages include an indication of the maximum communication time (T1) between the first device and the second device.

In the case of a connection between the first device belonging to a first radio frequency network and the second device belonging to a second radio frequency network, the method is characterized in that step (a) comprises the following steps:

(a send a communication request from the first device to the first control device of the first network, (a ₂ ) transmit this communication request from the first control device of the first network towards the second control device of the second network, and in that step (b) comprises the following steps: (b _x ) responding by the second control device to the first control device,

(b ₂ ) transmit this response from the first control device to the first device of the first network. The control device is a device dedicated to controlling communication requests.

The control device is a network device, one of the applications of which is to control communication requests. The invention also relates to a control device comprising a radio frequency communication interface and a microprocessor, characterized in that it contains a memory for storing data representing determined criteria and in that the microprocessor is able to use these criteria to authorize or refuse communication with a radio frequency device.

The control device is characterized in that it is portable and includes a smart card containing the determined criteria.

The control device is characterized in that the device is a chip support of the chip card type.

Other characteristics and advantages of the present invention will appear on reading the following description of a particular embodiment, said description being made in relation to the accompanying drawings in which:

FIG. 1 is a diagram of an elementary network of the BLUETOOTH type implementing the method according to the invention, FIG. 2 is a diagram illustrating the steps for the secure pairing of a device with an elementary network or Piconet,

FIG. 3 is a diagram illustrating the steps of the method according to the invention with a view to secure communication between two devices of an elementary network or Piconet,

FIGS. 4-a and 4-b are two simplified diagrams illustrating the result obtained thanks to the method described in relation to FIG. 3,

- Figure 5 is a diagram illustrating the steps of the method according to the invention for communication between two devices each belonging to a different Piconet. FIGS. 6-a and 6-b are two simplified diagrams illustrating the communication between two Piconets implementing the method according to the invention,

- Figure 7 is a diagram illustrating three piconets, and - Figure 8 is a diagram illustrating four piconets arranged hierarchically.

The invention will be described in its application to a radio frequency network 8 (FIG. 1) produced and operating according to the specifications of the above-mentioned BLUETOOTH system. This network or piconet 8 is for example provided for connecting a portable telephone device 10 (MP) to a listening headset 12 (HS) and to a personal computer 26 (PC), the latter being connected via the network 8 to a keyboard. 32. For this purpose, the various apparatuses or devices 10, 12, 26 and 32 are each equipped with a BLUETOOTH module 150 which transmits and receives radio signals via an antenna 14 for the portable telephone apparatus MP, 16 for the HS headset, 152 for PC personal computer, 154 for keyboard 32. In the current state of the BLUETOOTH system, the connection of a device to the network must be carried out according to a particular process which involves manipulation by the user of the device concerned, for example, by entering an access code by the keys 156 of the keyboard 32 or the keys 20 of the portable telephone apparatus 10. Other on / off 24 and "navigation" 22 keys on a screen 18 can also be used. In order to achieve secure pairing between two devices, for example between the portable device 10 and the listening earpiece 12, a process has been described in French patent application No. 00-09774 filed by the Applicant following steps :

(a) switch on the devices 10 (button 24) and 12; this start-up will in particular have the effect of operating the transceiver of each device and activating certain functions such as the display on a screen 18 and a keyboard 20 of the telephone device 10.

This screen 18 will display for example a menu of several choices, one of which will be called "PAIRING";

If the two devices are equipped with a screen and a keyboard, they will display the same menu. Also, in this case, the second step of the process consists in: (b) selecting one of the two devices as the master device and the other as the slave device. This selection has no reason to be in the case where only one of the two devices has a display screen and a selection keyboard, in which case it is the master device. As a result of this selection, the telephone device 10 behaves as a master device while the listening headset 12 behaves as a slave device. This selection being made, the third phase consists of:

(c) approach the two devices 10 and 12 so that their antennas 14 and 16 are in close proximity to one another. At the end of this step (c), the devices do not yet emit any radio frequency signal. The fourth step then consists in:

(d) launch on the master apparatus, that is to say the telephone apparatus 10, an automatic secure pairing procedure by selecting the option "PAIRING" on the menu proposed on screen 18 via the selection buttons 22.

This launch of the "PAIRING" procedure has the effect of making the two devices carry out the conventional procedure of connection to the radiofrequency network but with a very important difference: the transmitter of the master appliance transmits radiofrequency signals according to a diagram of radiation having an extremely short range so as to be intelligibly received only by another device in the immediate vicinity such as the headset 12.

As soon as the slave device is integrated into the radio frequency network by the conventional network procedure, the master device generates a PIN identification number

(PIN being the acronym for the Anglo-Saxon expression

"Personal Identity Nu ber" which is assigned to the slave device as well as a communication or transmission key which is then used to secure the subsequent exchange of information between the master device and the slave device. When the transmission key is known to both devices, the method according to the invention ends and this end is displayed on the screen 18 by an appropriate message. The master device transmits again according to the normal radiation pattern corresponding to the usual range. The two devices can then be distant from each other and continue their information exchanges according to the conventional network procedure, but these exchanges are secure thanks to the transmission key exchanged during pairing. If the process does not result in a pairing, this defect is signaled to the user by display or any other means. The user can then repeat the process in step (b) without changing the master device or by taking the other device as the master device when possible. This secure pairing method which has just been described makes it possible to improve security on entry into the network by limiting the range of the radiation diagram so as to only take into account devices in the immediate vicinity of a few centimeters. Such a way of doing things is not sufficient to guarantee the security of trade as mentioned above. The present invention makes it possible to guarantee the security of communications within secure piconets, according to the method described below.

The method of secure communication in a radio frequency network according to the invention is based on the use in each elementary PICONET network of a control device 40 called ΞM (SM being the acronym for the English expression "SMART MANAGER ") which authorizes or not, according to determined criteria, a device or device 42 to connect to another device or device of the network such as the headset 12. The determined criteria mentioned above correspond to a policy of communication which can be developed for each network by the owner of the devices. They can consist of making possible communications between such types of devices of the same network, for example a PC or a telephone. They also give the rules of communication between the network devices with certain types of external devices. They may also contain maximum periods of validity for each communication, provide for the authorization of the owner before establishing a communication. communications between the different radiofrequency devices are controlled and secured. The control device 40 has a microproc esseur and a radiofrequency communication interface and advantageously a smart card 136 in order to securely store the data corresponding to the determined communication and security criteria. It can be a specific device, dedicated to the control function or any network device in which this control function is integrated. Preferably, a device is chosen which is by nature carried by the user of the Piconet network, for example the MP mobile phone, the security criteria being able to be found on the SIM card (SIM is the acronym of the English expression Saxon “Subscriber Identity Module.” It can also be in the form of a simple smart card-type chip holder conforming to ISO 7816, containing a means of communication. BLUETOOTH and possibly a screen and / or a keyboard. Its microprocessor manages the process of one invention and is able to authorize or refuse communication according to the determined criteria. Firstly, the construction phase of a secure "PICONET" according to the invention will be described, it is broken down into two stages: first, each device is paired with the control device 40, then a communication key is established for each authorized pair of network devices.

The pairing phase is represented by the diagram in FIG. 2. The PDA device 42 for example, sends, in the immediate vicinity of the control device 40, a pairing request (arrow 50) to the control device SM 40 indicating its PIN1 number, which is its identification element, stored in the device 40. The device 40 checks whether this number is known to it (arrow 52). In the case where the device 42 meets for the first time the control device 40, the latter questions (arrow 54) the user 44 of the control device 40 on the response to be made to this request. In the event of a positive response (arrow 56) from the user 44, the control device 40 generates another PIN2 number (arrow 58) which is transmitted (arrow 60) to the PDA device 42 as well as a transmission key KT. At the end of steps 50 to 60, the PDA device 42 is assigned the PIN2 number which it registers with a view to using it during a next transmission. This PIN2 number is also recorded in the control device 40, indicating that it is assigned to the PDA device 42.

It is recalled that the pairing transmissions between the PDA device 42 and the control device 40 are carried out in the immediate vicinity of the two devices and low power as described in the aforementioned patent application. Steps 50 to 60 perform the pairing of any device with a device for controlling a secure Piconet according to the invention.

This pairing with the control device is carried out for each new device which wishes to be connected to a PICONET device so that all the PICONET devices are each assigned a PIN number which is registered in the corresponding device and in the device. control, the latter containing the list of all PIN numbers with possibly the identity of the corresponding devices, such as their PIN1 identification number and / or the type of device (printer, PC, telephone).

Then, a new step is necessary to allow the first communication between two devices paired with the same control device 40, for example the PDA 42 and the listening headset 12, which have been paired with a control device 40; they can start to communicate with each other through the following steps according to the invention which are described in relation to the diagram in FIG. 3 and the diagrams in FIGS. 4-a and 4-b.

The PDA device 42 transmits (arrow 70) a connection request to the listening earpiece HS 12 to the control device SM 40. If this connection request conforms to the determined criteria (arrow 72) recorded in the control device 40 , the method proceeds to step 80 which will be described below. Otherwise, the request is transmitted (arrow 74) to the user 44 for acceptance or refusal. In case of refusal, connection to the HS headset is not allowed. In case of acceptance, it is transmitted (arrow 76) to the control device 40 with indication of the duration of authorization Tl, which allows the latter to update its determined criteria (arrow 78) and generate (arrow 80) a communication key or KSI session between PDA device 42 and headset 12.

This session key KSI as well as the indication of authorization duration T1 are transmitted, on the one hand, to the PDA device 42 (arrow 82) using its transmission key KTa shared by the control device and the PDA device and , on the other hand, to the listening earpiece (arrow 84) using its transmission key KTb shared by the control device SM and the listening earpiece HS. When the PDA device and the HS headset have received the KSI session key, the PDA device can transmit (arrow 86) one or more audio files to the HS headset using the Ksi session key for the duration Tl indicated (arrow 88). At the end of the duration Tl, the transmission stops

(arrow 90). This period can also be unlimited.

In a second step, the PICONET being built and in normal operating mode, it will interact with external elements. Its control device 40 will control these interactions.

First, a PICONET device can be subjected to a communication request from an external device. In this case, it refuses the communication and the external device is directed to its control device 40, which starts, after verification of the determined criteria, a pairing procedure as defined above. The process is then equivalent to the introduction of the device into the PICONET described above. Then, two devices, each belonging to a different secure Piconet, may want to communicate. In this case, the steps of the process are illustrated by the diagram of there figure 5 and the diagrams of figures 6-a and 6-b in its application to the establishment of a connection between a first device PDAl belonging to a first Piconet PI comprising a first control device SM1 and a second device PDA2 belonging to a second Piconet P2 comprising a second control device SM2.

The first device PDA1 transmits (arrow 100) to the first control device SM1 a request for connection to the second device PDA2 associated with the second control device SM2. This request is analyzed (arrow 102) by the control device SM1 to determine whether it complies with the security criteria. In the event of a lack of conformity, the request is rejected. Otherwise, the first control device transmits (arrow 104) this connection request to the second control device SM2 which verifies its compliance with its security criteria (arrow 106). In case of compliance, the next step is to generate a KS2 session key (arrow 114) as will be explained below.

In the event of a conformity defect, the connection request is transmitted (arrow 108) to the user U2 of the second control device SM2. In the event of refusal, the connection is not authorized.

If accepted, it is transmitted (arrow 110) to the second control device SM2 with an indication of authorized duration T2. This information is used to update the security criteria (arrow 112). The second control device SM2 generates (arrow 114) a session key KS2 which is transmitted as well as the duration T2, on the one hand, to the second device PDA2 using a shared transmission key KTc (arrow 116) by SM2 and PDA2 and established according to the method described above in relation to FIG. 2 and, on the other hand, to the first control device SMl using a transmission key KTd (arrow 118) shared by SMl and SM2. The first control device SM1 then transmits (arrow 120) the session key KS2 and the duration T2 to the first device PDAl using a transmission key KTe shared by SMl and PDAl. Since the session key KS2 is known to PDAl and PDA2, PDAl directly transmits a file (arrow 122) to PDA2 using the key KS2, that is to say without the intervention of the control devices SM1 and SM2. The diagram in FIG. 7 shows an arrangement of three piconets Pi, P2 and P3 which provides the connection 130 between a PDAl device of a Piconet PI network (including SMl, PDAl, MPI and HS1 devices) and a listening earpiece HS3 of a Piconet P3 network (including SM3, PDA3, MP3 and HS3 devices) by using not only SM1 and SM3 control devices but also an SM2 intermediate control device that is part of a piconet including SM2 devices, PDA2, MP2 and HS2.

The diagram in FIG. 8 shows an arrangement of the three Piconets Pi, P2 and P3, the respective control devices SM1, SM2 and SM3 of which are connected to a fourth control device SM4 of a fourth Piconet P4 comprising the devices SM4 and MP4. According to the invention as described, a control device SM is assigned to each Piconet P network and is equipped with a communication circuit, for example operating according to the BLUETOOTH standard, capable of carrying out a secure pairing according to the method of the aforementioned patent application. This control device comprises a microcontroller capable of implementing the method according to the invention as well as the secure pairing method and of controlling a man / machine interface constituted for example by a screen 132 and keys 134. Each control device SM is associated with the user of the Piconet network who defines the rules or criteria for communication and security.

The same user can have several control devices if he uses several Piconet networks simultaneously. If these networks are only used separately, a single control device is sufficient, but it must contain the communication or security rules or criteria specific to each Piconet. This can be obtained with a control device equipped with a smart card reader, the memory of which contains the rules and criteria for control and security.

Thus, a user would be equipped with a single control device and would use an electronic chip card 136 per Piconet network: one for the office network, one for the personal network, one for the home automation space, etc.

Claims

1. A method of secure radio-frequency communication between a plurality of devices or apparatuses of a communication network, characterized in that it comprises the following steps consisting in:

(a) send a communication request (70) to a control device (40) of the communication network, and

(b) respond to this communication request (50 to 60 then 74 to 82) according to determined criteria.

2. Method according to claim 1, characterized in that the user of the control device (40) of the communication network defines at least one of the determined criteria.

3. Method according to claim 1 or 2, characterized in that the control device (40) of the communication network generates a negative response message when one of the determined criteria is not fulfilled.

4. Method according to claim 1 or 2, characterized in that the control device (40) of the communication network generates at least a first positive response message (82) to said communication request when the determined criteria are fulfilled, said first positive response message comprising at least one session key (KSI, KS2) to allow a first device of the communication network to communicate with at least one second device of the communication network.

5. Method according to claim 4 characterized in that the network control device (SM, 40) of communication generates a second positive response message (84) which is transmitted to a second device (HS, 12) of the communication network with which the first device wishes to communicate, said second message comprising said session key (KSI) which is used for communication between the first device (42) and the second device (12).

6. Method according to claim 4 or 5, characterized in that the first and the second positive response message (82, 84) comprise an indication of maximum duration (T1) of communication between the first device and the second device.

7. Method according to one of the preceding claims for connecting the first device (PDAl) belonging to a first radio frequency network (PI) and the second device (PDA2) belonging to a second radio frequency network (P2), characterized in that the step (a) includes the following steps:

(a send a communication request (100) from the first device (PDAl) to the first control device (SMl) of the first network, (a ₂ ) transmit this communication request (104) from the first control device (SMl) of the first network to the second control device

(SM2) of the second network, and in that step (b) comprises the following steps: (b respond (118) to the first control device

(SMl) by the second control device (SM2), (b ₂ ) transmit this response from the first control device (SMl) to the first device (PDAl) of the first network (PI).

8. Method according to any one of claims 1 to 7, characterized in that the control device is an apparatus dedicated to control communication requests.

9. Method according to any one of claims 1 to 7, characterized in that the control device is a network device, one of the applications of which is to control communication requests.

10. Control device (40) comprising a radiofrequency communication interface and a microprocessor characterized in that it contains a memory for storing data representing determined criteria and in that the microprocessor is able to use these criteria to authorize or refuse communication with a radio frequency device.

11. Control device (40) according to claim 10 characterized in that it is portable and comprises a smart card containing the determined criteria.

12. Control device (40) according to claim 10 characterized in that the device is a smart card type chip holder.