Secure connection of a station to an access point of a wireless telecommunications network

Abstract

A method for communication between at least one station (STA) and an access point (AP) of a wireless telecommunications network, wherein access to said access point is granted to a station for a time interval (P1, P2, P3) based on a security negotiation using at least one password, this method comprising steps implemented within a current time interval of: - dissemination (m1, m3) by the access point (AP) to the station (STA) of at least one new password associated with a new time interval, - establishment by the access point and the station of a new security negotiation (m2, m6) based on at least this new password before the end of the current time interval in order to renew access for the new time interval. Figure for the abstract: Fig. 2

Description

Title of the invention: Secure connection of a station to an access point of a wireless telecommunications network FIELD OF THE INVENTION

[0001] The present invention relates to the field of securing communications between one or more stations and an access point of a wireless telecommunications network, in particular a home Wi-Fi type network.

[0002] Different mechanisms have been proposed to secure communication between stations and access points. With regard to Wi-Fi networks, the WEP mechanism (for "Wired Equivalent Privacy" in English), specified by the IEEE 802.11 standard, the WPA2 mechanism (for "Wi-Fi Protected Access" in English), specified by the IEEE 808.1 li standard, and the WPA3 mechanism, dating from 2018, have succeeded each other.

[0003] Securing communications is based on authentication when a station accesses an access point and then encryption of the data exchanged once access is granted.

[0004] In a home network, the WPA-Personal mechanism, authentication is based on a secret shared between the two parties. This shared secret, called PSK for "Pre-Shared Key" in English, or previously shared key, is known to the access point and the station so that they can authenticate each other and allow the station access to the access point and, consequently, to the Wi-Fi radiocommunication network.

[0005] In France, ANSSI has issued recommendations on the choice of passwords, in order to limit the vulnerability of radiocommunication networks to cyberattacks, but across the world, other government agencies and others have issued recommendations going in the same direction.

[0006] The recommendations aim to increase the robustness of passwords. This robustness, or strength, depends in particular on its length, its complexity and its entropy.

[0007] A strong password makes it easier to resist a large number of cyberattacks, particularly those of the “brute force” or “downgrade attack” type.

[0008] In order to maximize this robustness, a number of rules have been issued, including: - Enforce a minimum length for passwords - Implement rules on password complexity

[0009] The disadvantage of these rules is the constraint they place on users. Even when strong passwords are initially set by telecommunications equipment manufacturers, users have the ability to change them and often opt for weaker passwords, which open the door to various types of possible cyberattacks.

[0010] There is therefore a need to improve current state-of-the-art proposals in order to make communications in radiocommunication networks more secure, without placing constraints on users. Summary of the invention

[0011] For these purposes, according to a first aspect, the present invention can be implemented by a method of communication between at least one station and an access point of a wireless telecommunications network, in which access to said access point is granted to said at least one station for a time interval as a function of a security negotiation based on at least one password, said method comprising steps implemented in a current time interval, of: - broadcasting by said access point to said at least one station of at least one new password associated with a new time interval, - establishment by said access point and said at least one station of a new security negotiation based on said at least one new password before the end of said current time interval in order to renew said access for said new time interval

[0012] Such a mechanism makes it possible to transfer the determination of at least one password to the access point. The latter can then determine a strong password, without this affecting the comfort of the user of the stations. The latter no longer even needs to choose a password, which improves the ergonomics of the installation and management of its Wi-Fi network in addition to the improvement in its security provided by the non-intervention of a human element.

[0013] Furthermore, the renewal mechanism over time makes it possible to respond to another ANSSI recommendation on password expiry times. Regardless of these recommendations, it is clear that renewing passwords reduces the time available for a cyber-attacker to determine a password. Furthermore, once compromised, the attacker will only be able to act during the time interval associated with this password.

[0014] In addition to the password, a new network identifier can be determined. This can be an SSID (for “Service SET Identifier”) type identifier which is a Wi-Fi type network identifier. Therefore, the terminology “at least one password” can include a pair formed of a network identifier and a password, the password being associated with the network identifier by this network identifier.

[0015] According to preferred embodiments, the invention comprises one or more of the following features which can be used separately or in partial combination with each other or in total combination with each other: - said establishment is triggered during a time window formed by the intersection between said current time interval and said new time interval. This time window can facilitate the establishment of a new security negotiation - said establishment is triggered at a random moment during said time window. This allows one to avoid occasional overloads of the access point. - as the end of said current time interval approaches, said at least one station transmits a password request to said access point if it has not received said broadcast of said at least one new password from said access point. This functionality allows stations that have not received the broadcasts to still be able to reconnect automatically (without human intervention) to the access point. - said stations determine a random time near said end to transmit said request. This can thus avoid occasional overloads of the access point. - said at least one password and said at least one new password are determined by said access point so as to maximize their robustness, by incorporating at least a portion of randomly selected characters. Due to the automatic nature (without human intervention), the passwords may be subject to a set of technical constraints aimed at optimizing their robustness and thus optimizing access security.

[0016] Another aspect of the invention relates to a communication station with an access point of a wireless telecommunications network, comprising a processor configured to obtain access to said access point for a time interval according to a security negotiation based on at least one password, and to, upon receipt of a message sent by said access point containing at least one new password associated with a new time interval, establish in collaboration with said access point a new security negotiation based on said at least one new password before the end of a current time interval, in order to renew said access for said new time interval.

[0017] Another aspect of the invention relates to an access point to a wireless telecommunications network, comprising a processor configured to grant access to a set of stations to said access point for a time interval according to a security negotiation based on at least one password, and for, in a current time interval: - broadcast to said set of stations at least one new password associated with a new time interval, - establish in collaboration with said set of stations a new security negotiation based on said at least one new password before the end of said current time interval in order to renew said access for said new time interval.

[0018] Another aspect of the invention relates to an Internet access box comprising an access point as previously described.

[0019] Another aspect of the invention relates to a mobile telecommunications terminal comprising an access point as previously described.

[0020] Another aspect of the invention relates to a computer program capable of being implemented on an access point to a wireless telecommunications network, the program comprising code instructions which, when executed by a processor, carry out the steps of the method as previously defined.

[0021] Other characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment of the invention, given by way of example and with reference to the appended drawings. BRIEF DESCRIPTION OF THE FIGURES

[0022] The attached drawings illustrate the invention: [Fig.l] illustrates a context for implementing a method according to one embodiment;

[0023] [Fig.2] shows a diagram of a timing diagram of an exchange between a station and an access point according to one embodiment of the method;

[0024] [Fig.3] schematizes a state graph of an embodiment of the part of the proposed process implemented by a station;

[0025] [Fig.4] illustrates a 4-pass handshake mechanism that may be used in one embodiment of the proposed method.

[0026] DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0027] [Fig.l] illustrates a context for implementing a telecommunications network enabling one or more stations to be connected to an access point.

[0028] This telecommunications network may be a wireless local telecommunications network (or radiocommunication), commonly called WLAN for “Wireless Local Area Network” in English.

[0029] This wireless local area network may comply with the Wi-Fi, or wifi, protocols as specified in the IEEE 802.11 family (or ISO / IEC 8802-11) standards documents.

[0030] Such a network is identified by a network identifier SSID (for “service set "identifier". In infrastructure mode (connecting a station to an access point), it is used to identify the wireless access point.

[0031] The stations can be of different natures, their common feature being to have means allowing connection to the network. These are essentially radiocommunication components and electronic and computer components allowing the implementation of the protocol stacks necessary for the management of the protocols associated with the network and the reception and transmission of data packets.

[0032] In [Fig.l], three types of STA stations are represented: a computer ORD, a mobile communication terminal, MOB, and a connected television TV.

[0033] The mobile terminal MOB is typically a smartphone type smart phone or a digital tablet.... The computer can be a fixed computer (or "desktop" according to the English vocabulary) or portable (or "laptop").

[0034] The TV can be natively connected or connected via an associated device such as, for example, an HDMI key connected to the TV.

[0035] An example of an external device communicating with a TV is Chromecast. Chromecast is a real-time media streaming device (media gateway) developed and marketed by Google. The device plugs into the HDMI port of a TV and communicates, via Wi-Fi, with another device connected to the Internet (computer, smartphone, tablet, etc.), in order to display on the TV the multimedia content received from an application compatible with Google Cast technology, from the Google Chrome browser on a computer, or from certain Android devices.

[0036] Obviously, other types of STA stations may be required to connect to a wireless local area network. These include connected objects which, in the context of the Internet of Things (IoT), connect to each other or to a server in order to deploy all of their functionalities.

[0037] According to an infrastructure deployment mode, the stations connect to the wireless local area network via one or more access points PA. These access points act as concentrators, through which the data flows from / to the stations necessarily pass.

[0038] These access points therefore allow the control of access to the wireless local area network by the STA stations. These must identify themselves to an access point and the latter, if necessary, grants them the rights corresponding to its profile. If it cannot identify itself correctly, the station cannot access the wireless local area network.

[0039] This local wireless telecommunications network may be a home network, i.e. corresponding to a user's home. Different users (corresponding to a family unit) may each use one or more stations. The same station may be used by several users, possibly in using different personal accounts.

[0040] The wireless local network can also be a business network, particularly for small businesses (SMEs / VSEs), places open to the public (restaurants, bars, cafes, etc.), etc.

[0041] Access points can also be of different types, in particular depending on the type of location in which the wireless local network is deployed.

[0042] An access point may be a dedicated device, marketed as such. It may also form, or be included in, a gateway to an external network such as the Internet.

[0043] For example, boxes allowing access to the Internet from a domestic environment usually offer the Wi-Fi access point function.

[0044] For example, in a domestic environment, the access point can be embedded in an internet connection box, commonly called an “internet box” or domestic gateway.

[0045] An access point may also be provided by a mobile telecommunications terminal (or a computer). These may form a gateway between a 3G / 4G / 5G cellular access radio network and a local Wi-Fi radio network, for example.

[0046] The connection, or access, of a station to an access point requires an authentication phase of this station STA with the access point PA.

[0047] In the context of a Wi-Fi network, the WPA2-Personal security mode can be used. Many devices are compatible with this security mode. It is particularly suitable for a home environment, in which access is controlled by secret phrases (or "passwords") and not by authentication servers such as Radius servers.

[0048] Other security modes are also possible, such as for example WPA3-Personal.

[0049] This authentication phase can be a 4-way handshake (or "4-way handshake" according to the more common terminology in English), as defined by the IEEE 802.11i standard. This standard defines an authentication mechanism commonly called WPA2 (for "Wi-Fi Protected Access 2" in English, or "protected access for Wi-Fi 2").

[0050] However, other mechanisms may be possible, in particular future developments of the protocols defined for Wi-Fi standards or for other families of protocols which could, for example, be derived from them.

[0051] This mechanism is an exchange of 4 messages passing between a STA station and an AP access point which allows: - confirm mutual knowledge of a common key and thus ensure a some form of authentication, and - derive and install temporal keys on the station and on the access point and provide assurance of the use of new encryption and integrity keys.

[0052] This common key can be a PMK (for “Pairwise Master Key” in English).

[0053] A deployment mode of a wireless local area network is called "personal" mode or PSK for "Pre-Shared Key" in English or pre-shared key. In this deployment mode, the master key PMK is calculated beforehand by the user of the station and the access point.

[0054] Typically, this PMK master key is derived from the PSK or, as commonly referred to, passphrase or password. The passphrase can be configured by an administrator within the access point settings.

[0055] In the following, the term “password” will be understood in its broadest sense, that is to say a series or string of characters which may include letters, numbers or other symbols.

[0056] Since these characters can include space, a password can therefore, semantically, contain several words. In such a situation, the term "passphrase" can be used. For the sake of clarity, we will subsequently consider that the term "password" covers the possibility that it is a passphrase.

[0057] In the proposed method, the password is determined by the access point. More precisely, the access point determines a password for a given time interval (or duration) and communicates it to the stations. At the end of this time interval, a new password is determined and communicated to the stations. At each time interval, a new authentication phase can be triggered based on the new password.

[0058] To the extent that the password is determined automatically (without human intervention) by the access point, without it being necessary to memorize or enter it, it may be subject to a set of technical constraints aimed at optimizing its robustness.

[0059] In particular, passwords must be decorrelated from users' personal data (date of birth, surname, city of birth, etc.), since this data can be learned by cyber-attackers and guide them towards the fraudulent determination of such passwords.

[0060] In particular, according to one embodiment, the passwords incorporate at least a portion of randomly selected characters. The random aspect makes it possible to maximize the internal entropy of the passwords, by decorrelating the probabilities of each constituent character: the probability of each character no longer depends on the characters. neighboring characters, as opposed to semantically significant words (true words).

[0061] Furthermore, to be robust, a password must be sufficiently long and sufficiently complex, that is to say, include characters of various types: uppercase letters, lowercase letters, numbers, symbols, etc.

[0062] Password scoring methods exist to determine the strength of a password based on the types of characters used and its length. Such a methodology can be used to automatically generate a password having a calculated strength exceeding a predetermined threshold.

[0063] The desired strength and the threshold may be parameters predetermined by the manufacturer of the access point and may possibly be modifiable by the latter, by software update (depending on new cyber-attacks detected for example), and / or by the user / administrator of the local radiocommunication network.

[0064] According to one embodiment, the password generation algorithm may be a software module adapted to be updated by the manufacturer of the access point or by a third party approved by the latter. It is thus possible to adapt the password construction methodology as soon as possible to recent cyberattacks.

[0065] [Fig.2] illustrates an example of implementation of the method in the form of a timing diagram.

[0066] This figure will be described in parallel with [Fig.3] which diagrams a state graph of an embodiment of the part of the proposed method implemented by an STA station.

[0067] In these figures, only one station is shown, but the general case applies to a set of stations which may include one or more station(s). Since the mechanism is independently implemented for each station (in the case where there are several), the description can refer to a single station without loss of generality.

[0068] Initially, the station STA is in a waiting state Ep. In this state, communication with the access point AP is established and secured, and the station is in its nominal operation.

[0069] Access has been previously granted for a time interval Pi by the generation of a first password by the access point AP.

[0070] During this time interval Pi the access point AP determines a new password for the next time interval P2.

[0071] This at least one password is broadcast to all the stations connected to the access point AP in a message mp A network identifier can also be broadcast, in association with the password.

[0072] By broadcasting, we mean the transmission of a data message intended for a plurality of stations. This may be a transmission of a frame in “broadcast” or “multicast” mode.

[0073] According to one embodiment, the message mi is an “Action Frame” as defined in section 8.5 of the IEEE 802.11 standard. Action frames are a type of management frame between access point and stations that allow an action to be triggered. Their use is fairly free and thus allows extensions of the management protocol.

[0074] According to a preferred embodiment, the message mi is protected, for example by the PMF mechanism, and encrypted with the group temporary key, GTK (for “Group Temporal Key”) derived from the password associated with the time interval Pb. The definition of a GTK key will be explored further below.

[0075] The message mi contains on the one hand a new password and a new associated time interval P2.

[0076] The new password can be generated in the same way as the previous one.

[0077] The time interval can be defined by two parameters, for example a start date and a duration (or an end date). It can in fact be provided that two successive time intervals overlap, that is to say that their intersection forms a time window At.

[0078] This time window At allows the establishment of a new security negotiation between the two parties. It can be planned according to a time required for this security negotiation, so that it can end before the end of the current time interval.

[0079] The time interval may be the same as the previous one, so that the time intervals form regular periods. It is also possible to define time intervals that vary over time. In particular, it may be planned to add a random element to the determination of the time intervals in order to make cyberattacks against the proposed mechanism more complicated.

[0080] When it receives the message mi, the station STA can move into a state E2 in which the station is ready to renew its access request to the access point. Just as in the state EB, the communication between the station STA and the access point AP is secure and corresponds to nominal operation.

[0081] The access request must be triggered so that the security negotiation can take place during the time window formed by the intersection between the current time interval (because the keys derived from the current password must still be valid) and the new time interval.

[0082] According to one embodiment, the establishment of the security negotiation can take place at a random instant during this time window At.

[0083] This random instant being a priori different for each station, the security negotiations are thus statistically distributed during the duration of the time window, so that the access point AP does not have to face all the ne negotiations at the same time. This avoids a one-off overload of the access point.

[0084] At the chosen instant within the time window At, the access point and the station STA (or, as a reminder, the stations) establish a new security negotiation m2 based on the new password in order to renew access for the new time interval P2. The station STA then enters a state E3 for renewing access.

[0085] This new security negotiation m2 aims to establish a new secure communication between station(s) and access point based on the new password. Once the new secure communication is established, the knowledge of the previous password that a cyber-attacker could have acquired would be useless to him.

[0086] In particular, this security negotiation makes it possible to derive, from the new password, one or more keys which are then used to encrypt the data exchanged between station(s) STA and access point AP.

[0087] According to one embodiment, the security negotiation comprises an authentication phase compliant with the IEEE 802.11i standard.

[0088] This authentication phase includes a 4-way handshake allowing the derivation of encryption keys.

[0089] In a Wi-Fi network-based embodiment, the password (or passphrase) may contain 8 to 63 ASCII characters or 64 hexadecimal symbols (256 bits). If a passphrase in the form of ASCII characters is used, it is converted to a 256-bit master key PMK, for example by applying a PBKDF2 key derivation function.

[0090] This PBKDF2 derivation mechanism (abbreviation of “Password-Based Key Derivation Function 2”) is for example described in the associated Wikipedia page: https: / / fr.wikipedia.org / wiki / PBKDF2.

[0091] The master key PMK is never directly used for encryption or integrity control. It is used for the generation of temporary encryption keys, PTK, for exchanges between a given access point AP and a given station STA.

[0092] The temporary PTK key (for “Pairwise Transcient Key”) actually comprises several temporal keys, each with a dedicated use: - the key confirmation key, KCK (for “Key Confirmation Key”), which is mainly used during the 4-way handshake, - the key encryption key, KEK (for “Key Encryption Key”), - the temporary key TK (for “Temporary Key”), - the temporary MIC key, TMK (“Temporary MIC Key”).

[0093] The temporary key PTK is derived from the master key PMK, a fixed character string, the MAC address of the access point, the MAC address of the station, and two random numbers generated one by the station and the other by the access point.

[0094] [Fig.4] illustrates the 4-way handshake mechanism that can be used in a embodiment of the proposed method.

[0095] In a first message, the access point AP transmits a first random number to the station STA which wishes to authenticate. According to the 802.1 li standard, this random number is called "Annonce".

[0096] In a step SI, the station STA generates a second random number, called “Snonce” according to the 802.1 li standard.

[0097] From two random numbers, the master key PMK, and the MAC addresses, the access point AP can determine the temporary key PTK.

[0098] The STA station can then transmit a message mh2 to the access point AP containing the second random number, Snonce, and an integrity code, MIC (for “Message Integrity Check”) using the key confirmation key, KCK (from the temporary key PTK).

[0099] This message mh2 is not encrypted. Upon receipt, in a step S2, the access point can therefore extract the second random number, Snonce. It can then calculate itself, in the same way as the access point, a temporary key PTK.

[0100] From this temporary key, the access point can then verify the integrity of the received message. This verification can consist of verifying the integrity of the integrity field MIC contained in the second message. It can thus ensure that the station STA knows the primary key PMK because it was able to correctly derive the temporary key PTK, then the temporal keys (key confirmation key, KCK) which allowed the generation of the integrity code, MIC.

[0101] The access point can verify the integrity of the mh2 message using the key in its possession.

[0102] If this key does not allow the integrity of the mh2 message to be verified, then the connection from the STA station is rejected.

[0103] In the favorable case, an mh3 message can then be transmitted to the STA station, in accordance with the specifications of the IEEE 802.11i standard.

[0104] This third message mh3 contains a group temporary key, GTK (“Group Temporal Key”), encrypted with the key encryption key, KEK, and derived from a group master key, GMK (“Group Master Key”) and a random number “GNonce”, as well as an integrity field, MIC, calculated on the content of this third message.

[0105] Upon receipt of this third message mh3, the station initiates a step S3 for verifying the integrity of the received message. This verification may consist of verifying the integrity of this integrity field MIC. This makes it possible to ensure that the access point knows the master key PMK and that it has correctly derived the temporary key PTK and then the temporal keys (in particular the key encryption key, KEK).

[0106] The fourth message, mh4, confirms the success of the entire 4-way handshake authentication phase. It indicates that the station has successfully installed the keys and is ready to begin encrypting the data. Upon receipt, both the station and the access point know that each party has obtained, calculated, and installed the various encryption keys for the protocol.

[0107] At this stage, the access point AP can actually connect the station STA to the local radiocommunication network, and they can exchange data by encrypting them with the keys derived and exchanged during this “4-way handshake” authentication phase.

[0108] These keys allow secure communication for the duration of the time interval P2 associated with the password which allowed them to be derived.

[0109] Once access (or connection) has been renewed, the STA station returns to the Ep waiting state

[0110] Thus, the proposed method is an iterative method aiming at each iteration to determine the parameters (password and time interval) of the following iteration.

[0111] According to one embodiment, the parameters also include a network identifier, for example of the SSID type (“service set identifier”) for a Wi-Fi type network. Thus, at each iteration, a new logical network is created to which the terminals must connect before the end of the term of the current network.

[0112] At the end of the current time interval, the current network can be made invalid by the server in order to prevent any terminal that has not implemented the described mechanism from being able to connect using an old Identifier / password pair.

[0113] Each iteration determines a time interval and at each current time interval Pn: - the access point broadcasts to all stations a new password, and possibly an SSID identifier, associated with a new time interval, Pn+i, and, - the access point and the stations establish a new security negotiation based on this new password, or on this identifier (SSID) / password pair, before the end of the current time interval Pn, in order to renew access for the new time interval Pn+i. Preferably, this new negotiation is established at a random time before the end of the current time interval Pn and after the start of the current time interval Pn+i.

[0114] The broadcast of the new password, the new network identifier (SSID) and the new time interval, Pn+i can be triggered several times during the duration of the current time interval Pn.

[0115] For example, we can define time intervals Pn of a duration of one month and plan to broadcast the information for the following time interval on a daily basis.

[0116] Obviously, once access is renewed, what was the new time interval becomes the current time interval (the value of iteration n incrementing for each interval).

[0117] In the example illustrated, in the same way as previously, during the new time interval P2 set up, the access point determines a new network identifier (SSID) and a new password associated with the future time interval P3. It broadcasts a message m3 to broadcast to the set of STA stations a new identifier / password pair and the new time interval P3.

[0118] Normally, the reception of this m3 message would trigger the transition of the STA station to state E2, as previously described.

[0119] In the illustrated example, however, it is assumed that the STA station does not receive this message m3. This situation can arise in different cases: the station was switched off when the message was broadcast, or it was out of range of the access point, etc.

[0120] According to one embodiment, several m3 broadcasts can take place during the same time interval P3 in order to minimize the risk that a station does not receive the new Identifier / password / time interval pair association before the moment when the renewal of access must be triggered. However, multiple broadcasts would have an impact both on the load of the local radiocommunication network and on security, each broadcast offering a new opportunity to potential cyber-attackers. And even in the case of several broadcasts (for example 1 per day for a time interval of one month), it may happen that these different broadcasts have not been correctly received by the station STA.

[0121] According to one embodiment of the invention, as the end of each time interval approaches, the STA stations transmit an m4 password request to the access point if they have not received the broadcast of the new password from the access point, and the associated network identifier.

[0122] Thus, the STA stations can control the approach of the end of the current time interval, by comparing the current clock and the time interval by means of a threshold ôt. If the current time is less than ôt from the end of the current time interval, then they go into state E4 and transmit a password request to the access point. In other words, the request m4 can be triggered when there is only one time ôt remaining before the end of the current time interval.

[0123] This threshold δ can be predetermined. It can be set as a compromise between a value that is too low, which would not allow enough time to receive the response from the access point, and a value that is too high, which would trigger a request before the broadcast message is received.

[0124] In order to prevent all or several stations from transmitting a request uq at the same time, thus overloading the access point, it may be provided that the stations determine a random instant as the end of the time interval approaches for transmitting said request. In other words, when the threshold ôt is crossed, each station may have a time window (less than this threshold ôt so as not to exceed the end of the time interval) in which to randomly determine an instant for triggering the transmission of the request m4

[0125] This m4 request is typically a unicast message intended for the AP access point.

[0126] According to one embodiment, the request m4 is an “Action Frame” as defined in section 8.5 of the IEEE 802.11 standard, just like the broadcast message mB m3.

[0127] In the same way, it can be protected, for example by the PMF mechanism, and encrypted with the key encryption key, KEK (“Key Encryption Key”) derived from the password associated with the current time interval.

[0128] Upon receipt, the access point AP transmits in a message m5 the new password associated with the new time interval, i.e. the same information as that broadcast in the message m3 previously sent.

[0129] This message m5 can therefore be semantically similar to the message m3. From a protocol point of view, the message m5 can be a message in “unicast” mode, while the message m3 was a broadcast message (multicast / broadcast).

[0130] Just like the mB m3 broadcast messages, according to a preferred embodiment, the message m5 is protected, for example by the PMF mechanism, but it is encrypted with the key encryption key, KEK (“Key Encryption Key”) derived from the password associated with the current time interval

[0131] This message may be identical to the broadcast message, but is in unicast mode instead of being in multicast or broadcast mode.

[0132] When it receives the message m5, the station STA can move into state E2 in which it is ready to renew its access request to the access point AP but waits for the end of the current time interval P3 to do so.

[0133] As previously described, the method provides for the establishment by the access point and the station of a new m6 security negotiation based on said new password before the end of this time interval in order to renew said access for said new time interval.

[0134] It may happen that the station cannot be granted access, for example in the case where its disconnection has lasted too long. When it transmits the password request, the current time interval has expired, and its request cannot be decrypted by the access point because the password having changed, the encryption keys (KEK) are no longer valid. In this case, the station can go into an E5 state requiring an au manual authentication by entering a password by the user. The automatic mechanism can be put back in place immediately or later but before the end of a first time interval associated with this manually entered password.

[0135] For STAs disconnected from the AP at the time of multiple renewal attempts, a new authentication would be necessary for each of them with entry of the password by the user.

[0136] Of course, the present invention is not limited to the examples and the embodiment described and shown, but is defined by the claims. It is in particular susceptible of numerous variants accessible to those skilled in the art.

Claims

Claims

1. Method of communication between at least one station (STA) and an access point (AP) of a wireless telecommunications network, in which access to said access point is granted to said at least one station for a time interval (Pb P2, P3) according to a security negotiation based on at least one password, said method comprising steps implemented in a current time interval, of: - broadcasting (mb m3) by said access point (AP) to said at least one station (STA) of at least one new password associated with a new time interval, - establishment by said access point and said at least one station of a new security negotiation (m2, m6) based on said at least new password before the end of said current time interval in order to renew said access for said new time interval.

2. Method according to the preceding claim, wherein said establishment is triggered during a time window formed by the intersection between said current time interval and said new time interval.

3. Method according to the preceding claim in which said establishment is triggered at a random instant during said time window.

4. Method according to one of the preceding claims, in which, as the end of said current time interval approaches, said at least one station (STA) transmits a request (mj) for a password to said access point (AP) if it has not received said broadcast (mb m3) of said new password from said access point (AP).

5. Method according to the preceding claim, in which said stations determine a random instant as said end approaches to transmit said request (rrq).

6. Method according to one of the preceding claims in which said at least one password and said at least one new password are determined by said access point so as to maximize their robustness, by incorporating at least a portion of randomly selected characters.

7. Station (STA) for communication with an access point (AP) of a wireless telecommunications network, comprising a processor configured to obtain access to said access point for a time interval as a function of a security negotiation based on at least one password, and to, upon receipt of a message sent by said access point containing at least one new password associated with a new time interval, establish in collaboration with said access point (AP) a new security negotiation based on said at least one new password before the end of a current time interval, in order to renew said access for said new time interval.

8. Access point (AP) to a wireless telecommunications network, comprising a processor configured to grant access to a set of stations to said access point for a time interval according to a security negotiation based on at least one password, and to, in a current time interval: - broadcast to said set of stations at least one new password associated with a new time interval, - establish in collaboration with said set of stations a new security negotiation based on said new password before the end of said current time interval in order to renew said access for said new time interval.

9. Internet access box comprising an access point according to the preceding claim.

10. Mobile telecommunications terminal comprising an access point according to claim 8.

11. A computer program capable of being implemented on an access point to a wireless telecommunications network, the program comprising code instructions which, when executed by a processor, performs the steps of the method defined in claims 1 to 6.

Images