EP1393527A1

EP1393527A1 - Method for authentication between a portable telecommunication object and a public access terminal

Info

Publication number: EP1393527A1
Application number: EP02745474A
Authority: EP
Inventors: Eric Malville; Didier Guerin; Yves Thorigne
Original assignee: France Telecom SA
Current assignee: Orange SA
Priority date: 2001-06-08
Filing date: 2002-06-03
Publication date: 2004-03-03
Also published as: US20040172536A1; FR2825869B1; FR2825869A1; WO2002102018A1; US7793102B2; JP2005504459A; JP4235102B2

Abstract

The invention concerns a method for authentication between a portable object (10) provided with an identifier (MSISDN) and a public access terminal (20) comprising: allocating to said portable object (10) a key (Kme); installing an authenticating server (30) capable of determining the key from said identifier (MSISDN); transmitting the identifier (MSISDN) to the authenticating server (30); determination by the server (30) of the key (Kme); allocation by the server (30) to a computing unit (30) the key (Kme); calculation by the computing unit (30) of a session key (Ksession) form said key (Kme); allocating the key (Ksession) to the public access terminal (20); transmission by the terminal (20) to the portable object (10) of a first signed message using the key (Ksession); acquisition from the key (Ksession) by the portable object (10) and authentication of the terminal (20) by the portable object (10); transmission by the portable object (10) to the terminal (20) of a second message, signed with the key (Ksession); and authentication of the portable object (10) by the terminal.

Description

AUTHENTICATION METHOD BETWEEN A PORTABLE TELECOMMUNICATION OBJECT AND A PUBLIC ACCESS TERMINAL

The present invention relates to an authentication method between a portable telecommunication object and a public access terminal. It also relates to a portable telecommunication object, a public access point and an authentication server, intended for the implementation of said method.

The invention finds a particularly advantageous application in the field of security of telecommunication services, and more particularly in that of securing connections when users equipped with a portable telecommunication object, such as a mobile phone, an assistant. Personal (PDA), laptop, etc., seek to access private resources via public access terminals.

In this context, public access terminals include telecommunication means on a telecommunication network which allow users to benefit, for example, from broadband access to their mobile portal from their portable telecommunication object. This broadband access is made possible, on the one hand, thanks to the capacities of the access network, preferably of ADSL type (from 512 to 1024 kbits), and, on the other hand, thanks to the capacities of communication links without wire (700 kbits), whether it is a short-distance radio link, such as that known as Bluetooth, or an infrared link. As can be seen, the throughput capacities of the two elements constituted by the access network and the wireless link are similar, which guarantees a high flow of information all along the communication chain. For this, of course, the portable telecommunication object and the public access point must be equipped with respective wireless communication means.

The access of a user to his mobile portal can be envisaged in the following way: 1. The user connects to a public access point with his mobile phone via a Bluetooth link for example. The terminal and the mobile phone authenticate each other, the mobile phone being identified by his MSISDN number (Mobile Subscriber ISDN Number), and, optionally, the user of the mobile phone himself is authenticated.

2. Thanks to the MSISDN number of the mobile phone, a URL server allows the public base station to retrieve the URL of the user's mobile portal. The connection is secured by mutual authentication between the terminal and the server and by encryption and / or authentication of messages using an appropriate protocol such as the protocol known as SSL v3.

3. The public access point thus connects to the portal transparently by transmitting a signed token, such as the MSISDN number or another identifier, certifying the identity of the mobile phone. The use of the SSL v3 protocol allows the public access point and the mobile portal to authenticate each other and, possibly, to ensure the confidentiality and / or integrity of the information exchanged. The terminal therefore behaves like a trusted third party vis-à-vis the portal by guaranteeing the authentication of the mobile phone. If user authentication is carried out via the mobile phone, the latter then acts as a trusted third party vis-à-vis the terminal and the portal.

4. At the end of these steps, the mobile phone, and if necessary its user, is identified with the portal. The public access point then acts as a relay between the different users and their portal: it transmits the requests to the portal and returns the results to the users.

The question which arises in this access procedure is to be able to carry out the authentication of the portable telephone by the public access terminal through a wireless communication of the Bluetooth type, as it appears in step 1.

However, if the Bluetooth security services, for example, make it possible to establish secure connections between several personal devices, the latter must therefore share the same secret (a PIN identification code). The security protocol proposed by Bluetooth is therefore not sufficient, in itself, to ensure a secure connection between several users and public equipment. Indeed, Bluetooth security is designed to respond to private use where the various devices with the Bluetooth interface and capable of communicating with each other are in limited number and can authenticate each other thanks to the secret they share in common. This secret is the key element of security.

We conclude that the recommended implementation of Bluetooth security is not applicable to the context of the invention because it assumes a private environment, while the authentication sought here between a public access point and at least one mobile phone must take place in a public environment. Indeed, the simple sharing of the same secret is not enough to guarantee authentication by the terminal of the different mobile phones taken individually, because it is necessary that each mobile phone has its own secret, and that each public terminal has knowledge of this secret.

Also, the technical problem to be solved by the object of the present invention is to propose an authentication method between, on the one hand, a portable telecommunication object assigned a unique identifier and comprising first means of wireless communication. , and, on the other hand, a public access point comprising second wireless communication means, able to cooperate with said first means, and telecommunication means on a telecommunication network, which method would allow communication to be established secure wireless between the portable telecommunication object and the public access point so as to ensure, on the one hand, mutual authentication between the portable object and the terminal, and, on the other hand, encryption of the communications.

The solution to the technical problem consists, according to the present invention, in that said method comprises the following operations: - allocation to said portable telecommunication object of a wireless communication key,

- installation on said telecommunication network of an authentication server capable of determining the wireless communication key of the portable object from said unique identifier, - transmission, of the portable object to the public access terminal, the unique identifier of the portable object, through said first and second wireless communication means,

- transmission, from the public access terminal to the authentication server, of the unique identifier of the portable object, through said telecommunication means, - determination by the authentication server of the wireless communication key of the portable object from the unique identifier transmitted,

- allocation, by the authentication server, to a unit for calculating said wireless communication key, - calculation by the unit for calculating a session key from said object's wireless communication key portable,

- allocation of said session key to the public access point,

- transmission by the public access terminal to the portable object, through said first and second wireless communication means, of a first signed message implementing the session key,

- acquisition of the session key by the portable object from the first message and the wireless communication key, and authentication of the public access terminal by the portable object by verifying the signature of said first signed message, - transmission by the portable object to the public access terminal, through said first and second wireless communication means, of a second message, signed with the session key, and authentication of the portable object by the terminal public access by verifying the signature of said second signed message. Thus, the determination of a cryptographic key, here the session key, carried out by both the portable object and the public access terminal from the key of the portable object suitable for the wireless communication service ensures mutual authentication of the portable object and of the terminal, as well as it allows the confidentiality of information by encryption of the exchanges. Many variants of implementation of the authentication method according to the invention will be described in detail below. However, we can already mention some of them.

In particular, concerning the determination of the wireless communication key of the portable telecommunication object by the authentication server, the invention provides two possible embodiments. According to a first mode, the wireless communication key of the portable object is determined by the authentication server from the unique identifier of the portable object and from a master key using a diversification mechanism. According to a second mode, the wireless communication key of the portable object is determined by the authentication server from the unique identifier of the portable object by consulting a storage table.

As for the means for the portable object to acquire the session key, two possibilities are offered by the invention, namely, either the acquisition of the session key by the portable object is carried out by calculation by the object portable of said session key from said first message and the wireless communication key, ie the acquisition of the session key by the portable object is carried out by transmission by the public access terminal to the portable object a first signed message containing said session key encrypted with the wireless communication key of the portable object, and decryption by the portable object.

As regards the calculation of the session key following the allocation by the authentication server of the wireless communication key of the portable object, it is provided, in accordance with the invention, that the unit of calculation of the session key is constituted by the authentication server, or else the session key calculation unit is constituted by the public access terminal.

Finally, it should be noted that two usage configurations can be envisaged for the public access terminal. According to a first configuration, the terminal only serves as a relay to the telecommunications network, the services being consulted by the user on his own portable object. According to a second configuration, the public access terminal has the particularity that it has a user interface comprising a display screen, the consultation of the services then being carried out on the screen of the terminal itself. It should however be emphasized that these two configurations are not mutually exclusive insofar as the relay type terminal is also included in the terminal with screen. In this case, of course, only one user has access to the terminal screen, the others then having to use their portable object, this within the limits of the capacity of the terminal to enter into communication with different portable objects.

Another important aspect of the invention concerns the authentication, not only of the portable object as explained above, but of the user himself so as to ensure, if necessary, that it is indeed owner of the equipment he uses. To this end, the authentication method according to the invention is supplemented by the fact that it comprises an operation of authenticating a user by entering a secret specific to said user and comparing the secret entered with a secret of reference. In a first mode of implementation, said secret is a personal code entered by the user, this code possibly being of the type known by the PIN code used in particular for securing electronic payment cards. In a second embodiment, said secret is a biometric fingerprint entered by the user, such as a fingerprint.

After entering the secret by the user, the authentication proper is carried out by comparison with the reference secret, either by the portable telecommunication object or by the public access terminal.

When said comparison is carried out by the portable object, user authentication takes place as follows:

1. Entering the secret by the user.

Two cases are to be considered: a) The user enters his secret on his portable object. b) The user enters his secret on the terminal, which certifies the physical presence of the user near the terminal. In this case, the terminal must have input equipment (fingerprint sensor, touch screen, ...). The secret entered is sent encrypted to the portable object. An anti-replay mechanism, by using a random variable, a shared counter, a time element, ensures that the message transmitted is not an old message. Several portable objects can be detected simultaneously by the terminal, the invention further recommends displaying on the terminal all of the portable objects detected and compelling the user to select the one he uses, so as to that the secret is not sent to all connected portable objects. The user recognizes his mobile, for example, by his Bluetooth address, his serial number or any other information that differentiates him from other portable objects. The terminal checks beforehand that no portable object detected by the terminal has the same identifier.

2. Recovery of the reference secret. In this approach, the reference secret is stored in the portable object, or equipment attached to the portable object, such as an additional card, for example a SIM card. 3. Verification of the secret seized. The verification is carried out on the portable object which compares the secret entered with the reference secret. If the verification is positive, the portable object sends a confirmation message to the public access point. This message is signed by means of a cryptographic mechanism with public key - digital signature - or by means of a secret key mechanism - a method of authentication of messages, such as a MAC (Message Authentication Code) thus allowing the terminal to verify the authenticity and the non-replay of this message. The portable object therefore presents itself as a trusted item of equipment with respect to the terminal. It is he who certifies that the user is indeed the owner of the portable object. When said comparison is made by the public access point, user authentication takes place as follows:

1. Entering the secret by the user.

Two cases are to be considered: a) The user enters his secret on the portable object. In this case, the secret entered is sent encrypted to the public access point. An anti-replay mechanism, by using a random variable, a shared counter, a time element, ensures that the message transmitted is not an old message. b) The user enters his secret on the terminal, which certifies the physical presence of the user near the terminal.

2. Recovery of the reference secret.

Two alternatives are possible: a) The reference secret, signed if necessary by an entity recognized by the terminal, is stored in the portable object and sent encrypted to the terminal. In the first case, the invention recommends compelling the user to select the portable object that he uses so as to avoid that all connected portable objects have to systematically send the reference secret to the terminal. b) The reference secret is stored in the authentication server and retrieved by the terminal from the unique identifier of the portable object. 3. Verification of the secret seized.

The public access point then compares the secret entered and the reference secret to authenticate the user. It can also, optionally, ensure that the user is the owner of the portable object by consulting the authentication server.

At the end of these steps, the portable object and the user are authenticated, the terminal is therefore able to authorize access to the local resources of the recognized user or to certify the identity of the user to remote private resources, such as a mobile portal, the terminal in this case playing the role of trusted intermediary. The information is then either displayed on the terminal screen or transmitted to the user's portable object.

In the case where the user's secret is a biometric characteristic, the invention recommends not keeping the reference secret in the authentication server but in the portable object itself, if necessary in signed form. The signature will be that of an entity recognized by the terminal. The purpose of this provision is then to avoid the storage of physiological data of users in a database, which could pose difficulties vis-à-vis official bodies responsible for the protection of privacy. In addition, when authentication is carried out by the public access terminal, the reference biometric characteristics must be sent to the terminal which performs the verification. An alternative could be for the portable object to require the biometric characteristics entered from the terminal and to carry out the verification itself before sending the reference minutiae to the terminal. The description which follows with reference to the appended drawings, given by way of nonlimiting examples, will make it clear what the invention consists of and how it can be implemented.

FIG. 1 is a diagram illustrating a method of mutual authentication between a portable object and a public access point. FIG. 2a is a diagram illustrating a method of authenticating a public access terminal by a portable object.

Figures 2b and 2c are diagrams illustrating, in combination with Figure 2a, two modes of authentication of a portable object and its user by a public access point. FIG. 3 is a diagram describing the disconnection of a portable object from a public access point.

In Figure 1 is shown schematically an authentication method between, on the one hand, a portable telecommunication object 10 which, in the example of Figure 1, is a mobile phone, called "mobile" in the following of this description, assigned a unique identifier MSISDN, and on the other hand, a public access terminal 20 comprising telecommunication means on a telecommunication network 1.

The mobile 10 and the terminal 20 are capable of exchanging information through a wireless communication link of the Bluetooth type for example. For this, the mobile and the terminal are respectively provided with first and second wireless communication means.

The mutual authentication of the mobile 10 and of the terminal 20 is carried out by sharing a session key between the mobile and the terminal according to a method the steps of which will now be described in detail.

1. The mobile 10 is assigned a wireless communication key Kme, shared with the terminal 20.

2. On the telecommunication network 1 is installed an authentication server 30 capable of determining the key Kme of the mobile wireless communication from the unique identifier MSISDN.

3. The public access terminal 20 is activated by the mobile 10 in accordance with the teaching of patent application 00 09438 in the name of the Applicant.

4. During the connection phase, the mobile 10 generates a first random random number and transmits to terminal 20 its identifier MSISDN as well as said first random random number through said first and second wireless communication means. This transmission can be signed by the Kme key of the mobile or by a trusted authority.

5. In turn, the terminal 20 transmits the unique identifier MSISDN and the random random number to the authentication server 30 through said telecommunication means. The use of a protocol such as SSL v3 allows mutual authentication between the terminal 20 and the authentication server 30.

6. The authentication server 30 then proceeds to determine the key Kme of the mobile 10 from its identifier. In the example of FIG. 1, the key Kme is determined from the unique identifier MSISDN and from a key- Master Kmaître stored in the authentication server 30, using a diversification mechanism. Another alternative for determining the key Kme of the mobile 10 is possible, consisting in consulting a storage table in which the keys Kme associated with all the mobiles subscribed with the service are recorded.

7. The key Kme being known, the authentication server 30 generates a second random number random2 and calculates a session key Ksession from the key Kme of the mobile 10 and the two random numbers aleal and random2.

8. The authentication server 30 returns to the public access terminal 20 the session key Ksession, the identifier MSISDN of the mobile 10 and the second random number random 2. An encrypted connection, using the SSL v3 protocol for example, guarantees the confidentiality of information.

9. Terminal 20 sends a first messi message to mobile 10 containing the two random numbers aleal and random2 signed with the session key Ksession.

10. The mobile 10 then acquires the session key Ksession by calculation from the two random numbers contained in the first messi message and from its wireless communication key Kme, stored in the mobile 10 or in the SIM card. The calculation of the key Ksession by the mobile 10 is identical to the calculation of the same key by the authentication server 30. The mobile 10 then verifies the signature of the first messi message calculated by the terminal 20. At the end of this step, the public access terminal 20 is authenticated.

11. Finally, the mobile sends to terminal 20 a second mess2 message signed with the session session key. To avoid the risks of replay, this second message mess2 can be deduced from the two random numbers aleal and alea2 thanks to a function which must be known by the mobile 10 and the terminal 20. For example, it can simply be 'a message containing the two random numbers incremented by 1. Terminal 20 verifies the signature of the second mess2 message sent by the mobile 10. At the end of this step, the mobile 10 is authenticated.

The authentication method of the invention has just been described by implementing a unit for calculating the session key Ksession constituted by the authentication server 30. It should however be pointed out that the said calculation unit could just as easily be constituted by the public access terminal 20 itself. In this case, the authentication server 30 returns to terminal 20 the MSISDN identifier of the mobile 10 accompanied by the key Kme which it has determined. Terminal 20 generates the second random number random 2 and calculates the key Ksession from the key Kme of the mobile 10 and the two random numbers. Similarly, a variant to the acquisition by calculation of the session key

Ksession by the mobile 10 consists in transmitting by the public access terminal 20 a first signed message containing said key Ksession encrypted with the key Kme of the mobile, and decrypting the key Ksession by the mobile 10.

FIGS. 2a, 2b, 2c describe two modes of implementation of a mutual authentication method between a public access terminal 20 and the user of a mobile 10. This authentication is carried out in two stages: the first illustrated by FIG. 2a concerns the authentication of the terminal, while the second user authentication step is represented by the two variants of FIGS. 2b and 2c. Note that this second step also allows the terminal 20 to authenticate the mobile 10.

As can be seen in FIG. 2a, the step of authenticating the public access terminal 10 is carried out in a manner analogous to the diagram in FIG. 1, namely by sharing a session key Ksession between the mobile 10 and terminal 20:

1. The mobile 10 sends its unique identifier MSISDN, its physical Bluetooth address BD ADDR and a first random random number to terminal 20.

2. Terminal 20 transmits the MSISDN identifier of the mobile 10 and the random random number to the authentication server 30. The use of an SSL v3 connection allows mutual authentication between the terminal 20 and the authentication server 30.

3. The authentication server 30 calculates the session key Ksession. To do this, it starts by calculating the key Kme specific to the mobile 10 from a Kmaître master key using a diversification mechanism and the MSISDN identifier. It then generates a second random number random2 and calculates the session key Ksession from the key Kme of the mobile 10 and the two random numbers.

4. The authentication server 30 returns the MSISDN identifier of the mobile 10, the second random number random2 and the session key Ksession at terminal 20. The SSL v3 connection makes it possible to guarantee the confidentiality of the information by encryption. 5. Terminal 20 sends in a first message Messi 1 the two random numbers signed to mobile 10.

6. The mobile 10 calculates the session key Ksession from its own key Kme and from the two random numbers. This session key allows it to verify the signature of terminal 20 and thus ensure that the terminal is a trusted terminal.

7. If the terminal 20 screen is available, the terminal displays the list of Bluetooth BD ADDR physical addresses of the mobiles present in the terminal field.

At the end of these steps, neither the mobile 10 nor the user is yet authenticated.

Two alternatives are offered to the user to authenticate with public access terminal 20: biometric authentication on the terminal

20 (FIG. 2b) and authentication by PIN code on the mobile 10 (FIG. 2c).

In both cases, this authentication phase allows the terminal 20 to authenticate the mobile. Biometric authentication on terminal 20 is carried out as described in FIG. 2b assuming that the screen of terminal 20 is available:

1. The user selects his mobile 10 from the list of physical addresses

Bluetooth presented on the terminal 20 screen. 2. Terminal 20 asks the user to enter his fingerprints using the biometric fingerprint sensor.

3. The terminal 20 sends in a second first message messi 2 the minutiae and the first random random number to the mobile 10. The message is encrypted with the session key Ksession. 4. The mobile 10 deciphers the message messi 2, checks the validity of the aleal random number and compares the minutiae entered with the reference minutiae. If the correspondence is correct, the user is considered to be authenticated by the mobile 10.

5. If the user is authenticated, the mobile 10 sends in a second message mess2 the reference minutiae of the user and the identifier MSISDN signed by an authority recognized by the terminal and a random number calculated from the second random number random2 at terminal 20. The message is encrypted with the Ksession session key. 6. Terminal 20 decrypts said second message mess2, and thus authenticates mobile 10, verifies the signature of the authority, verifies the validity of the random number received and compares the minutiae entered with the reference minutiae. If the verification is correct, terminal 20 considers the user as authenticated.

7. The user accesses the resources using the screen of the public access terminal 20.

Authentication by PIN code on the mobile 10 shown in FIG. 2c allows users to connect to a terminal 20, either when the latter is unavailable, or when they do not wish to use the terminal screen.

In this case, authentication of the user and of terminal 20 is carried out as follows:

1. The user explicitly requests the connection by using, for example, a key on the mobile 10 specific to the service. 2. The mobile 10 displays a form for entering the PIN code.

3. The mobile 10 sends in a second message mess2 its unique identifier MSISDN, the PIN code and a random number calculated from the second random number random 2 at terminal 20. The message is encrypted with the session key Ksession.

4. Terminal 20 decrypts the message mess2, and thus authenticates the mobile 10, and checks the validity of the random number received.

5. Terminal 20 interrogates the authentication server 30 to recover, from the identifier MSISDN, the user's reference PIN code. The use of an SSL v3 connection allows mutual authentication between the terminal 20 and the authentication server 30 as well as encryption of the communications.

6. Terminal 20 compares the PIN code entered with the reference PIN code. If the verification is correct, the user is considered as authenticated by the terminal.

7. Terminal 20 returns to mobile 10 the result of authentication. When the authentication is correct, the user can access the resources by his mobile 10.

In FIG. 3, it can be seen that the disconnection can either be explicitly requested by the user, or be carried out automatically when the mobile 10 leaves the field of the public access terminal 20. In both cases, if terminal 2 is available, the updated list of Bluetooth physical addresses detected by terminal 20 is displayed on the screen.

Claims

1. Authentication method between, on the one hand, a portable telecommunication object (10) assigned a unique identifier (MSISDN) and comprising first wireless communication means, and, on the other hand, a terminal ( 20) public access comprising second wireless communication means, able to cooperate with said first means, and telecommunication means on a telecommunication network (1), characterized in that said method comprises the following operations:

- allocation to said portable telecommunication object (10) of a wireless communication key (Kme),

- installation on said telecommunication network (1) of an authentication server (30) capable of determining the key (Kme) of wireless communication of the portable object (10) from said unique identifier (MSISDN),

- transmission, from the portable object (10) to the public access terminal (20), of the unique identifier (MSISDN) of the portable object, through said first and second wireless communication means,

- transmission, from the public access terminal (20) to the authentication server (30), of the unique identifier (MSISDN) of the portable object (10), through said telecommunication means,

- determination by the server (30) of authentication of the key (Kme) of wireless communication of the portable object (10) from the unique identifier (MSISDN) transmitted, - allocation, by the server (30) authentication, to a unit (20, 30) for calculating said wireless communication key (Kme),

- calculation by the unit (20, 30) of calculating a session key (Ksession) from said wireless communication key (Kme) of the portable object (10),

- allocation of said session key (Ksession) to the public access terminal (20), - transmission by the public access terminal (20) to the portable object (10), through said first and second means of wireless communication, of at least a first signed message (messi; mess11, messi 2) implementing the session key (Ksession),

- acquisition of the session key (Ksession) by the portable object (10) from the first message (messi; messi 1; messi 2) and the key (Kme) of wireless communication, and authentication of the public access terminal (20) by the portable object (10) by checking the signature of said first message (messi; messi 1, messi 2) signed,

- transmission by the portable object (10) to the public access terminal (20), through said first and second wireless communication means, of a second message (mess2), signed with the key (Ksession) of session, and authentication of the portable object (10) by the public access terminal (20) by verifying the signature of said second message (mess2) signed.

2. Authentication method according to claim 1, characterized in that the transmission by the portable object (10) of the unique identifier (MSISDN) is signed by the wireless communication key (Kme).

3. authentication method according to claim 1, characterized in that the transmission by the portable object (10) of the unique identifier (MSISDN) is signed by a trusted authority recognized by the unit (20, 30) Calculation.

4. authentication method according to any one of claims 1 to 3, characterized in that the key (Kme) of wireless communication of the portable object (10) is determined by the authentication server (30) to from the unique identifier (MSISDN) of the portable object (10) and a master key (Kmaître) using a diversification mechanism.

5. Authentication method according to any one of claims 1 to 3, characterized in that the key (Kme) of wireless communication of the portable object (10) is determined by the authentication server (30) to starting from the unique identifier (MSISDN) of the portable object (10) by consulting a storage table.

6. Authentication method according to any one of claims 1 to 5, characterized in that the acquisition of the session key (Ksession) by the portable object (10) is carried out by calculation by the portable object ( 10) of said session key (Ksession) from said first message and of the wireless communication key (Kme).

7. Authentication method according to claim 6, characterized in that the calculation of the session key (Ksession) by the portable object (10) is identical to the calculation of the session key (Ksession) by the unit ( 20, 30) of calculation.

8. Authentication method according to one of claims 6 or 7, characterized in that the calculation of the session key (Ksession) is carried out using a first random number (aleal) generated by the portable object (10) and passed on to said calculation unit (20, 30), and a second random number (random 2) generated by the calculation unit (20, 30) and transmitted to the portable object (10).

9. Authentication method according to claim 8, characterized in that the unique identifier (MSISDN) is transmitted by the portable object (10) to the calculation unit (20, 30) with the first random number (aleal ).

10. Authentication method according to one of claims 8 or 9, characterized in that the first signed message contains at least said second random number (random2) signed with the session key (Ksession).

11. Authentication method according to any one of claims 1 to 5, characterized in that the acquisition of the session key (Ksession) by the portable object (10) is carried out by transmission by the terminal (20) public access to the portable object (10) of a first signed message containing said session key (Ksession) encrypted with the wireless communication key (Kme) of the portable object (10), and decryption by l portable object (10).

12. Authentication method according to any one of claims 1 to 11, characterized in that the unit for calculating the session key (Ksession) is constituted by the authentication server (30).

13. Authentication method according to any one of claims 1 to 11, characterized in that the unit for calculating the session key (Ksession) is constituted by the public access terminal (20).

14. Authentication method according to any one of claims 1 to 13, characterized in that it comprises an operation of authenticating a user by entering a secret specific to said user and comparing the secret entered with a secret reference.

15. Authentication method according to claim 14, characterized in that said secret is a personal code (PIN) entered by the user.

16. Authentication method according to claim 14, characterized in that said secret is a biometric fingerprint entered by the user.

17. Authentication method according to any one of claims 14 to 16, characterized in that the reference secret is stored in the portable object (10).

18. Authentication method according to any one of claims 14 to 16, characterized in that the reference secret is stored in the authentication server (30).

19. Authentication method according to any one of claims 14 to 18, characterized in that said comparison is carried out by the portable object (10).

20. Authentication method according to any one of claims 14 to 18, characterized in that said comparison is carried out by the public access terminal (20).

21. Portable telecommunication object (10) for implementing the authentication method according to any one of claims 1 to 20, characterized in that it comprises: - a unique identifier (MSISDN),

- wireless communication means,

- a wireless communication key (Kme),

means for acquiring a session key (Ksession) from a first signed message implementing said session key (Ksession) and the wireless communication key (Kme),

means for authenticating the first message by verifying the signature of said first signed message.

- Means for transmitting, through said wireless communication means, a second message signed with the session key (Ksession).

22. Portable telecommunication object (10) according to claim 21, characterized in that said acquisition means consist of means for calculating the session key (Ksession) from the first message and the key (Kme) wireless communication.

23. Portable telecommunication object (10) according to claim 22, characterized in that it comprises means for generating random numbers (aleal).

24. Portable telecommunication object (10) according to any one of claims 21 to 23, characterized in that it comprises means for storing a reference secret specific to a user.

25. Object (10) of portable telecommunications according to claim 24, characterized in that it comprises means of comparison between said reference secret and a secret entered by the user.

26. Portable telecommunication object (10) according to any one of claims 21 to 25, characterized in that said means of Wireless communication are short distance wireless radio link means.

27. Public access terminal (20) for implementing the authentication method according to any one of claims 1 to 20, characterized in that it comprises:

- wireless communication means,

- telecommunication means on a telecommunication network,

- means for storing a session key (Ksession),

means for transmitting, through said wireless communication means, a first signed message implementing the session key (Ksession),

means for authenticating a second message signed with the session key (Ksession), by verifying the signature of said second signed message.

28. Public access terminal (20) according to claim 27, characterized in that it constitutes a unit for calculating said session key (Ksession).

29. Public access terminal according to one of claims 27 or 28, characterized in that it comprises means of comparison between a secret entered and a reference secret.

30. Public access terminal (20) according to any one of claims 27 to 29, characterized in that it has a user interface comprising a display screen.

31. Public access terminal (20) according to any one of claims 27 to 30, characterized in that said wireless communication means are short distance wireless radio link means.

32. Authentication server (30) for implementing the authentication method according to any one of claims 1 to 20, characterized in that it comprises:

- telecommunication means on a telecommunication network,

means for determining a key (Kme) for wireless communication of a portable object from a unique identifier (MSISDN) of said portable object,

means for assigning said wireless communication key (Kme) to a session key calculation unit (Ksession).

33. Authentication server (30) according to claim 32, characterized in that said determination means are capable of determining the key (Kme) of wireless communication from the unique identifier (MSISDN) and a master key (Kmaître) using a diversification mechanism.

34. Authentication server (30) according to claim 32, characterized in that said determination means are capable of determining the key (Kme) of wireless communication from the unique identifier (MSISDN) by consulting a storage.

35. Authentication server (30) according to any one of claims 32 to 34, characterized in that it constitutes said calculation unit.

36. Authentication server (30) according to any one of claims 32 to 35, characterized in that it comprises means for storing a reference secret of a user.