WO2017095303A1

WO2017095303A1 - Provisioning node, communication node and methods therein for handling key identifiers in wireless communication

Info

Publication number: WO2017095303A1
Application number: PCT/SE2016/051151
Authority: WO
Inventors: Piergiuseppe DI MARCO; Per Skillermark; Roman CHIRIKOV; Wei Shen
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2015-12-04
Filing date: 2016-11-18
Publication date: 2017-06-08

Abstract

A provisioning node (100), a communication node (106) and methods therein, for handling key Identifiers, key IDs, used in wireless communication. The provisioning node (100) monitors (1:1) usage of key IDs in multiple wireless communications networks (102), and generates (1:2) a new key ID associated to a security key, for use in a first wireless communications network (104). The new key ID is verified (1:3) when the monitored usage of key IDs indicates that the new key ID is not already used in any of the monitored networks (102). The provisioning node (100) then distributes (1:4) the unique new key ID to communication nodes (106) in the first network (104). One or more of the communication nodes (106) may transmit a beacon comprising a list of currently used key IDs to enable the provisioning node (100) to verify the new key ID by comparing it to the key IDs in the list.

Description

PROVISIONING NODE, COMMUNICATION NODE AND METHODS THEREIN FOR HANDLING KEY IDENTIFIERS IN WIRELESS COMMUNICATION

Technical field

The present disclosure relates generally to a provisioning node, a communication node, and methods therein, for handling key Identifiers, key IDs, used in wireless communication.

Background

In the field of wireless communication, the term "wireless device" is often used to represent any communication entity capable of radio communication with a wireless communications network by sending and receiving radio signals, such as e.g. mobile telephones, tablets, laptop computers and Machine Type

Communication, MTC, devices also known as Machine-to-Machine, M2M, devices. Another common generic term for wireless device is "User Equipment, UE".

Further, the term "network node" is generally used to represent a node of a radio network that communicates radio signals with wireless devices. A network node could also be referred to as a base station, radio node, e-NodeB, eNB, NB, base transceiver station, access point, etc., depending on the type of network and terminology used.

In wireless communications networks it is common that data packets sent in the air over a radio interface have been authenticated and encrypted so that the content of such a packet when received by a receiver can be accessed only if the receiver has the correct and valid keys for decryption. The receiver or destination of the packet can thus authenticate the packet as being sent from a sending node with access to the same keys and ascertain that the packet content was not altered in transit from sender to receiver. A communication node, such as a wireless device, may have key(s) associated to the network(s) it belongs, to be able to access information used to forward packets, and key(s) associated to the application(s) the network supports, in order to decrypt and access the application payload, i.e. the packet content. Such keys for encryption and decryption are sometimes referred to as security keys. Keys are typically distributed, also referred to as provisioned, to a communication node before the node is able to join a network and communicate messages therein. In some cases, a pointer called key identifier, or "key ID" for short, is inserted in a Protocol Data Unit, PDU, header which is typically attached to the message or packet. Without the key ID, upon receiving a packet or message, a communication node would have to check each incoming packet against all known keys. The communication nodes in a wireless communications network may further belong to different security groups, each security group having its own set of keys and associated key IDs. In general terms, communication nodes sharing the same security keys and corresponding key IDs are said to belong to the same security group.

By attaching a key identifier to an encrypted message it is possible to identify which subset of keys have been used to encrypt and secure the message and any extra unsuccessful decryption attempts by a non-valid key can thereby be avoided. For example, instead of checking all the known keys, a communication node may only need to check the keys that have the same key ID. If a message or packet is received with a key ID that is not known to the communication node, then the node can discard that message or packet since it was evidently intended for a

communication node of another network or security group. The key ID is typically generated using a key derivation function from the security key.

A special case may occur when using a security key that is associated to a specific network, i.e. a network key. In this case, a pointer called "network ID" is inserted in the PDU header. Without the network ID, upon receiving an encrypted packet from a neighbour network, a communication node would have to always check the incoming packet against its network key. By using the network ID, it is possible for communication node to identify whether an incoming packet belongs to its network and avoid extra unsuccessful decryption attempts.

Security keys and corresponding Key IDs are obtained or generated independently by each network. When many wireless networks coexist in the same area, or many applications are running on the same communication nodes or devices, the probability of having packets or messages in the air encrypted by different security keys but having the same key ID in their PDU headers, may become considerable. The unnecessary cost for processing and discarding messages and PDUs encrypted with unknown keys that use the same Key ID may be high.

Ideally, a communication node belonging to a first security group should try to decrypt and process only messages and PDUs generated within the first security group based on the key IDs of that security group. However, a second security group may use the same key IDs that are used by the first security group, thus causing unnecessary actions in the communication node of the first security group for processing a message of the second security group, such as multiple

Advanced Encryption Standard, AES, operations, to decrypt the message or packet before discarding it.

Summary

It is an object of embodiments described herein to address at least some of the problems and issues outlined above. It is possible to achieve this object and others by using a provisioning node, a communication node and methods therein as defined in the attached independent claims.

According to one aspect, a method is performed by a provisioning node for handling key Identifiers, key IDs, used in wireless communication. In this method, the provisioning node monitors usage of key IDs in multiple wireless

communications networks. The provisioning node further generates a new key ID associated to a security key, for use in a first wireless communications network, and verifies the new key ID when the monitored usage of key IDs indicates that the new key ID is not already used in any of the monitored wireless

communications networks. The provisioning node then distributes the new key ID to communication nodes within the first wireless communications network.

Thereby, it is an advantage that the new key ID can be used in the first wireless communications network without the risk of collision with conflicting key IDs, e.g. referred to as "key ID collision", that might otherwise occur if the same key ID is already used in one or more other wireless communications networks. Hence, the risk that the new key ID is the same as a key ID that is associated with another security key in another network, is virtually eliminated or at least minimized, and any unnecessary costs for processing and discarding messages and PDUs encrypted with unknown keys that use the same Key ID can be avoided.

According to another aspect, a provisioning node is arranged to handle key Identifiers, key IDs, used in wireless communication. The provisioning node is configured to monitor usage of key IDs in multiple wireless communications networks, and to generate a new key ID associated to a security key, for use in a first wireless communications network. The provisioning node is also configured to verify the new key ID when the monitored usage of key IDs indicates that the new key ID is not already used in any of the monitored wireless communications networks, and to distribute the new key ID to communication nodes within the first wireless communications network.

According to another aspect, a method is performed by a communication node for handling key Identifiers, key IDs, used in wireless communication in a wireless communications network. In this method, the communication node transmits a beacon that can be received by a provisioning node. The transmitted beacon comprises a network identifier and a list of key IDs currently used in the wireless communications network. Thereby, the provisioning node is enabled to verify a new key ID when determining that the new key ID is not equal to any key ID in said list.

According to another aspect, a communication node is arranged to handle key Identifiers, key IDs, used in wireless communication in a wireless communications network. The communication node is configured to transmit a beacon that can be received by a provisioning node, the beacon comprising a network identifier and a list of key IDs currently used in the wireless communications network, thereby enabling the provisioning node to verify a new key ID when determining that the new key ID is not equal to any key ID in said list.

The above methods, provisioning node and communication node may be configured and implemented according to different optional embodiments to accomplish further features and benefits, to be described below. A computer program is also provided which comprises instructions which, when executed on at least one processor, cause the at least one processor to carry out either of the methods described above. A carrier containing the above computer program is further provided, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

Brief description of drawings

The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

Fig. 1 is a communication scenario where a provisioning node handles key IDs, according to some possible embodiments.

Fig. 2 is a flow chart illustrating a procedure in a provisioning node, according to further possible embodiments.

Fig. 3 is a flow chart illustrating an example of how a provisioning node may operate, according to further possible embodiments. Fig. 4 is a flow chart illustrating another example of how a provisioning node may operate, according to further possible embodiments.

Fig. 5 is a block diagram illustrating a provisioning node and a communication node in more detail, according to further possible embodiments.

Detailed description

Briefly described, a solution is provided to avoid that a new key identifier provisioned in a first wireless communications network is confused with any existing key identifier(s) used in any other wireless communications network. This is achieved by monitoring traffic in other wireless communications networks and usage of key identifiers associated with different encryption keys, herein referred to as security keys. A new key identifier can then be verified for use in the first network if it is found to be unique and thus not used in any other network, based on said monitoring. The term "verified" thus indicates that the risk that the new key identifier is the same as a key identifier that is associated with another security key in another network, is virtually eliminated or at least minimized. Such conflict of key identifiers may be referred to as "key identifier collision".

The above monitoring and verifying may be realized by functionality in a

provisioning node which is operable to handle key identifiers, or key IDs for short, for one or more wireless communications networks including at least the first wireless communications network. The provisioning node may belong to or be associated to the first wireless communications network, or it may be implemented as a central function providing key IDs to multiple wireless communications networks. By monitoring traffic and usage of key IDs in the other wireless communications networks, the provisioning node is able to identify which key IDs are already "occupied" so that a new key ID can be generated for the first network that is different and distinct from all the key IDs used in the other networks. The provisioning node described herein may alternatively be termed key manager, key ID generator, key provider, and so forth. Fig. 1 illustrates a provisioning node 100 which is responsible for generating and providing security keys and corresponding key IDs to different wireless

communications networks 102. Fig. 1 further illustrates an example where the provisioning node 100 generates and distributes a key ID to communication nodes in one of the networks 106, referred to as a first wireless communications network 104. The key ID may for example identify the network 104 itself or some service application being supported by the network 104.

Fig. 1 also illustrates that various wireless devices 106 communicate messages with network nodes within their respective networks 102 where one or more key IDs may be included in the messages, e.g. in a PDU header of the message as mentioned above. A "message" in this context could be any type of communication of information, such as a data packet or similar, that can be encrypted or otherwise protected by means of a security key as provided by the provisioning node 100. It is thus assumed that a communication node receiving the message can only access its content by using the correct security key. The wireless devices 106 may include any type of entities capable of communicating messages or data packets with a network, such as e.g. mobile phones, smartphones, tablets, portable computers, machine-to-Machine, M2M, devices, and so forth. The term "communication node" is used herein to generally denote any entity that communicates messages and/or data packets in a wireless communications network, such as a wireless device. A communication node in this context may also be a network node such as a base station, an access point, a gateway, a central node, etc., depending on the type of network and terminology used. Further, the provisioning node described herein may be implemented in a central node serving several wireless communications networks, or in a node belonging to or associated with the first wireless communications network, or in a wireless device being responsible for generating and distributing security keys and key IDs.

It will now be described how a provisioning node may operate in a procedure for handling key IDs used in wireless communication, with reference to the flow chart in Fig. 2. The provisioning node in this example corresponds to the provisioning node 100 in Fig. 1 and further reference will be made to entities and actions in Fig. 1 which figure illustrates an example of how the procedure of Fig. 2 may be used in a practical communication scenario. A first action 200 illustrates that the provisioning node 100 monitors usage of key IDs in multiple wireless communications networks 102, which is also indicated by dashed two-way arrows in an action 1 :1. This monitoring operation may be performed any number of times and/or for any duration, e.g. on a more or less continuous basis or during a predefined probing period which may be repeated according to a predefined scheme. In practice, the provisioning node 100 may monitor the usage of key IDs by obtaining traffic information from nodes in each network 102. It is also possible that the provisioning node may monitor the usage of key IDs in the networks 102 such that nodes in the first network 106 may relay traffic information from the other networks 102 to the provisioning node 100, thus employing "multi-hop" monitoring. In a further action 202, the provisioning node generates a new key ID associated to a security key, for use in a first wireless communications network 104, such as the network 104 in Fig. 1 . This is also shown in an action 1 :2. The security key itself may be generated or otherwise obtained by the provisioning node 100 which is however outside the scope of this procedure. In a few non-limiting examples, the new key ID may be generated more or less randomly, or based on the security key, or based on some other parameter or identity associated to the first wireless communications network. Furthermore, it may not be necessary in action 200 above for the provisioning node 100 to monitor usage of key IDs in the first wireless communications network 104, at least not for the purpose of providing a new key ID for that network 104.

In another action 204, the provisioning node 100 is able to verify the new key ID when the monitored usage of key IDs indicates that the new key ID is not already used in any of the monitored wireless communications networks 102, which is also shown in an action 1 :3. Thereby, the new key ID can be used in the first wireless communications network 104 without the risk of collision that would otherwise occur if the same key ID is already used in one or more other wireless

communications networks 102.

Thus, if the monitored usage of key IDs would indicate that the new key ID is actually used in another wireless communications network, this key ID will not be distributed to and used in the first wireless communications network 104 and another key ID can instead be generated and compared to the monitored usage of key IDs in the wireless communications networks 102. The operations of generating a new key ID and comparing it to key IDs used in the other monitored networks 102 may thus be repeated until a unique new key ID is obtained that is not used in the other networks. If there is no such unique key ID, a new key ID may be selected that is not likely to collide with another existing key ID which may be determined based on conflict reports during a probing period when the key ID is "tested", to be described below. A final action 206 illustrates that the provisioning node distributes the new key ID to communication nodes 106 within the first wireless communications network 104. This is also shown in action 1 :4. This distribution may e.g. be accomplished in practice by sending the new key ID to network nodes in the first wireless

communications network 104 such that the network nodes, not shown, can then broadcast or otherwise transmit the new key ID to any communication nodes 106 served by and/or monitoring the network nodes.

It should be noted that actions 200-206 and actions 1 : 1 - 1 :4 may be performed in a different order than shown in the figures. For example, actions 200 and 1 : 1 may be performed any time throughout the procedure, e.g. on a more or less

continuous basis and/or at predefined intervals. In another example, actions 202 and 1 :2 may be performed before actions 200 and 1 : 1 , respectively. In another example, actions 202, 206 and 1 :2, 1 :4 may be performed e.g. before actions 200, 204 and 1 : 1 , 1 :3, respectively, such that a generated and distributed temporary new key ID is "tested" during a probing period before it is verified, which will be described in more detail below with reference to Fig. 4. The procedure described above may further be employed for generating and distributing more than one new key ID to network 104, e.g. a set of key IDs to be used for different applications and/or security groups in the network 104, and the solution is not limited in this respect.

Various optional and non-limiting embodiments can be used in the above- described procedure as follows. In one possible embodiment, said monitoring in actions 200, 1 : 1 may comprise collecting key IDs from the messages

communicated in the monitored wireless communications networks, and said verifying may in that case comprise determining that the new key ID is different from all key IDs already used in the monitored wireless communications networks according to said monitoring.

This embodiment is further illustrated by the flow chart in Fig. 3 where key IDs are obtained and collected from messages communicated in the other networks, in an action 300, and a new key ID is generated by the provisioning node in action 302. It is then checked in another action 304 if the new key ID is equal to any of the collected key IDs. If so, the generated key ID is discarded and actions 302 and

304 are repeated until a newly generated key ID is found that is not equal to any collected existing key ID, i.e. the new key ID is unique. In that case, the new key ID can be verified and distributed as shown in action 306.

As long as no unique key ID is found, actions 302 and 304 may be repeated several times, e.g. until a timeout is reached or until all possible key IDs have been evaluated. For example, the size of the key ID may be limited depending on space available in a PDU header determining the number of bits or the like that can be used, so that the number of possible key IDs is relatively small and all of them may already be used in the other networks. If no unique key ID can be found, the provisioning node may select and distribute a key ID that is likely to cause as few key ID collisions as possible or at least within a tolerable level.

In another possible embodiment, the key IDs used in the other networks may be obtained from a Protocol Data Unit, PDU, header attached to the messages, e.g. in action 300 above. In another possible embodiment, the monitoring and verifying may be repeated at predefined intervals, or at least once. Thereby, it can be checked that the key ID distributed in actions 206, 1 :4 is still unique across the networks. If not, there is a risk for key ID collision and the key ID used so far can be discarded and another new key ID may be generated, checked, verified and distributed in the manner described above.

In another possible embodiment, the new key ID may be used and tested in the first wireless communications network 104 during a certain probing period. In that case, said verifying may be performed based on whether any report of conflict between the new key ID and a key ID already used in the monitored wireless communications networks, has been received from the first wireless

communications network 104 during the probing period according to said monitoring. If a probing period is used according to the latter embodiment, another possible embodiment could be that the probing period is initiated after the new key ID has been distributed to communication nodes 106 within the first wireless communications network 104.

The latter two embodiments are further illustrated by the flow chart in Fig. 4 where a new key ID, denoted "temporary key ID", is first generated in an action 400, and the temporary key ID is distributed to communication nodes within the first wireless communications network 104 in action 402. Another action 404 illustrates that the provisioning node waits until the probing period has expired, during which "normal operation" is applied using the temporary key ID. It is then checked in an action 406 if any conflict(s) with key ID collision has been reported during the probing period. If so, the generated temporary key ID is discarded and actions 400-406 are repeated until no conflict(s) with key ID collision has been reported for a newly generated temporary key ID. In that case, the new key ID can be verified and continued to be used, as shown in action 408. In another possible embodiment, the probing period may be repeated at least once to determine whether the new key ID needs to be changed. In another possible embodiment, the new key ID could be verified if the number of received reports of conflict is not above a threshold, e.g. zero. If just a few key ID collisions can be tolerated, the threshold may be set to a number larger than zero, depending on implementation. A possible modification of the above-described procedure in Fig. 4 may accordingly be that it is checked in action 406 whether the number of received reports of conflict is not above a threshold that is above zero, and that actions 400-406 are repeated until the number of received reports of conflict does not exceed the threshold. In another possible embodiment, said monitoring may comprise receiving beacons transmitted from communication nodes 106 in the monitored wireless

communications networks 102, each beacon comprising a network identifier and a list of key IDs currently used in the respective network. In that case, said verifying may comprise determining that the new key ID is not equal to any key ID in said list. Functionality in a communication node to enable the latter embodiment will be described below with reference to Fig. 5.

In another possible embodiment, the new key ID may be distributed to

communication nodes of a security group in the first wireless communications network 104. Hence, any of the above procedures of Figs 2-4 may be performed to generate and distribute new key IDs to communication nodes of multiple different security groups in the first network 104. In another possible embodiment, the security key may be associated to the first wireless communications network 104 or to an application supported by the first wireless communications network 104. In another possible embodiment, said generating of the new key ID may comprise applying a key derivation function to the security key. Alternatively, the new key ID may be generated more or less randomly or based on a parameter or identity associated to the first wireless communications network 104, as also mentioned above.

Various features and characteristics of the embodiments herein will now be further elaborated below. It was mentioned above that in conventional usage of key IDs there is a risk that the same key ID is used by more than one network or security group, independently of one another, as a pointer to a security key that is not the same in the different networks or security groups, herein referred to as key ID collision. This problem may thus be overcome or at least reduced by employing the solution and its embodiments described herein. A brief analysis of the probability of such key ID collision across multiple networks and security groups in case the above-described solution is not employed is presented below.

In this analysis it is assumed that there are N networks, each network having K security groups, and key IDs of B bits are randomly generated for the networks and security groups. The probability of key ID collision, P_co\\ , at one of the networks can be

approximated by the following formula:

Assume N=10, K=2, B=5, we obtain Pcoll~44%. Consequently, almost half of the times a packet or message is received by a communication node there will be traffic from other networks "leaking" into the first network. These PDUs of the packets or messages are discarded only after a number of unsuccessful and costly AES operations. Note that the collision probability between security keys is instead negligible by construction since the amount of bits in the security keys is much larger than in the key IDs (e.g., 128-bit security keys guarantees 2128 different combinations).

In some of the embodiments described herein, the provisioning node responsible for generating the security key and the associated key ID monitors the traffic generated by existing neighbour networks and security groups, and collects information about the key IDs used by such networks. Then, the provisioning node generates a security key and associated key ID so that the key ID is different from all the collected ones. The procedure may be repeated periodically to account for newly formed networks and security groups.

Embodiments have also been described above where the provisioning node may generate the security key and a temporary key ID which are distributed to the communication nodes in the first wireless communications network, e.g. to a particular security group therein. Communication nodes detecting a collision between the temporary key ID and an existing key ID should in some

embodiments report the collision to the provisioning node within the above- described probing period. If no key ID collision is reported within the probing period, the temporary key ID is verified and confirmed for use in the network or security group. The amount of collision reports from the communication nodes can be used to prioritize the appropriate key for the provisioning node to select.

In another embodiment, the detection of colliding key IDs is performed by monitoring the traffic by receiving control packets, i.e. the above-described beacons, transmitted by communication nodes in the networks. For example, all mains powered devices in all the networks may be configured to transmit such a beacon periodically. Such beacons may contain a network ID and a list of key IDs of groups to which the device or communication node belongs.

The embodiments described herein could also be utilized to mitigate the collisions of network IDs. There are some existing solutions used for ID conflict resolution in personal/local area networks. In the patent document US 8072962 B2, a method of detecting and solving a network ID conflict in personal area networks is provided. The method involves end-nodes generating and transmitting reports that include an "extended ID", to help detecting ID conflicts at the network coordinator. In the patent document EP 2670207 A1 , a method for negotiating network ID renewal among network coordinators is proposed. Compared to US 8072962 B2, EP 2670207 A1 , and any other existing technology, the scope of the embodiments described herein is significantly different. The main advantages of the solution and embodiments described herein may include the following:

• Any risks of unnecessary decryption operations at a wireless device, such as AES operations, in the presence of multiple security groups can be reduced, thus saving energy and computational complexity for wireless devices and the network operation. · Key ID collisions can be detected by any node attempting to decrypt a PDU with a known key ID. In the above-mentioned US 8072962 B2, it is necessary to exchange extra information between a communication node and a coordinator. In EP 2670207 A1 , it is necessary to receive information from another coordinator in order to detect a key ID collision. In this disclosure, it is described how a provisioning node may be configured and operate, the provisioning node being responsible for generating and distributing the security keys in the network.

In the embodiments described herein, it may be further assumed that the key ID is transmitted unencrypted in a data PDU header of each message, such that a receiver of the message is able to detect and read the key ID in the PDU header without having to decrypt the key ID. The receiver of a message with such a data PDU header is also denoted "communication node" herein.

As mentioned above, beacons may be transmitted by mains powered devices e.g. according to a predefined scheme. If the devices transmit a list of key IDs in the beacon, it can be assumed that after a certain period of time most, or even all, key IDs of the security groups of all the neighbour networks will be available to the provisioning node.

The beacon may include: · Network ID

• List of key IDs

The block diagram in Fig. 5 illustrates a detailed but non-limiting example of how a provisioning node 500 and a communication node 502 may be structured to bring about the above-described solution and embodiments thereof. The warning system 500 may be configured to operate according to any of the examples and embodiments of employing the solution as described above, where appropriate, and as follows. Each of the provisioning node 500 and the communication node 502 is shown to comprise a processor P and a communication unit C with suitable equipment for transmitting and receiving radio signals in the manner described herein.

The communication circuit C in each of the provisioning node 500 and the communication node 502 thus comprises equipment configured for communication using a suitable communication protocol depending on the implementation. The solution is however not limited to any specific types of messages or protocols. The actions shown in Figs 1 -4 may be performed by means of functional modules in the respective processors P in the provisioning node 500 and the

communication node 502. For example, the provisioning node 500 comprises means configured or arranged to perform at least some of the actions of the flow charts in Figs 2-4 in the manner described above. Further, the communication node 502 comprises means configured or arranged to operate in the manner described above. In the following description of Fig. 5, reference will also be made to corresponding entities in Fig. 1 . The provisioning node 500 is arranged to handle key Identifiers, key IDs, used in wireless communication. The provisioning node 500 thus comprises the processor P and the memory M, said memory comprising instructions executable by said processor, whereby the provisioning node 500 is operative as follows. The provisioning node 500 is configured to monitor usage of key IDs in multiple wireless communications networks 102. This operation may be performed by a monitoring module 500A in the provisioning node 500, e.g. in the manner described for action 200 above. The provisioning node 500 is also configured to generate a new key ID associated to a security key, for use in a first wireless communications network 104. This operation may be performed by a generating module 500B in the provisioning node 500, e.g. in the manner described for action 202 above.

The provisioning node 500 is further configured to verify the new key ID when the monitored usage of key IDs indicates that the new key ID is not already used in any of the monitored wireless communications networks 102. This operation may be performed by a verifying module 500C in the provisioning node 500, e.g. in the manner described for action 204 above. The provisioning node 500 is also configured to distribute the new key ID to communication nodes within the first wireless communications network 104. This operation may be performed by a distributing module 500D in the provisioning node 500, e.g. in the manner described for action 206 above.

The communication node 502 is arranged to handle key IDs used in wireless communication in a wireless communications network. The communication node 502 is configured to transmit a beacon that can be received by the provisioning node 500, the beacon comprising a network identifier and a list of key IDs currently used in the wireless communications network. This operation may be performed by a transmitting module 502A in the communication node 502. Thereby, the provisioning node 500 is enabled to verify a new key ID when determining that the new key ID is not equal to any key ID in said list. The communication node 502 may be further configured to send a report of conflict to the provisioning node 500 when detecting that the new key ID collides with a key ID already used in the wireless communications network.

It should be noted that Fig. 5 illustrates various functional modules in the provisioning node 500 and the communication node 502, respectively, and the skilled person is able to implement these functional modules in practice using suitable software and hardware. Thus, the solution is generally not limited to the shown structures of the provisioning node 500 and the communication node 502, and the functional modules 500A-D and 502A therein may be configured to operate according to any of the features and embodiments described in this disclosure, where appropriate.

The functional modules 500A-D and 502A described above may be implemented in the provisioning node 500 and the communication node 502, respectively, by means of program modules of a respective computer program comprising code means which, when run by the processor P causes the provisioning node 500 and the communication node 502 to perform the above-described actions and procedures. Each processor P may comprise a single Central Processing Unit (CPU), or could comprise two or more processing units. For example, each processor P may include a general purpose microprocessor, an instruction set processor and/or related chips sets and/or a special purpose microprocessor such as an Application Specific Integrated Circuit (ASIC). Each processor P may also comprise a storage for caching purposes.

Each computer program may be carried by a computer program product in each of the provisioning node 500 and the communication node 502 in the form of a memory having a computer readable medium and being connected to the processor P. The computer program product or memory M in each of the provisioning node 500 and the communication node 502 thus comprises a computer readable medium on which the computer program is stored e.g. in the form of computer program modules or the like. For example, the memory M in each node may be a flash memory, a Random-Access Memory (RAM), a Readonly Memory (ROM) or an Electrically Erasable Programmable ROM (EEPROM), and the program modules could in alternative embodiments be distributed on different computer program products in the form of memories within the respective provisioning node 500 and communication node 502.

The solution described herein may be implemented in each of the provisioning node 500 and the communication node 502 by a computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions according to any of the above

embodiments, where appropriate. The solution may also be implemented at each of the provisioning node 500 and communication node 502 in a carrier containing the above computer program, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

While the solution has been described with reference to specific exemplifying embodiments, the description is generally only intended to illustrate the inventive concept and should not be taken as limiting the scope of the solution. For example, the terms "provisioning node", "wireless communications network",

"communication node", "security key", "key identity", "probing period" and "beacon" have been used throughout this disclosure, although any other corresponding entities, functions, and/or parameters could also be used having the features and characteristics described here. The solution is defined by the appended claims.

Claims

1 . A method performed by a provisioning node (100) for handling key Identifiers, key IDs, used in wireless communication, the method comprising:

- monitoring (200) usage of key IDs in multiple wireless communications networks (102),

- generating (202) a new key ID associated to a security key, for use in a first wireless communications network (104),

- verifying (204) the new key ID when the monitored usage of key IDs indicates that the new key ID is not already used in any of the monitored wireless

communications networks (102), and

- distributing (206) the new key ID to communication nodes (106) within the first wireless communications network (104).

2. A method according to claim 1 , wherein said monitoring comprises collecting key IDs from messages communicated in the monitored wireless communications networks (102), and wherein said verifying comprises determining that the new key ID is different from all key IDs already used in the monitored wireless communications networks (102) according to said monitoring.

3. A method according to claim 2, wherein the key IDs are obtained from a Protocol Data Unit, PDU, header attached to the messages.

4. A method according to claim 2 or 3, wherein the monitoring and verifying are repeated at predefined intervals.

5. A method according to claim 1 , wherein the new key ID is used in the first wireless communications network (104) during a certain probing period, and wherein said verifying is performed based on whether any report of conflict between the new key ID and a key ID already used in the monitored wireless communications networks, has been received from the first wireless communications network (104) during the probing period according to said monitoring.

6. A method according to claim 5, wherein the probing period is initiated after the new key ID has been distributed to the communication nodes of the first wireless communications network (104).

7. A method according to claim 5 or 6, wherein the probing period is repeated at least once to determine whether the new key ID needs to be changed.

8. A method according to any of claims 5-7, wherein the new key ID is verified if the number of received reports of conflict is not above a threshold.

9. A method according to any of claims 1 -8, wherein said monitoring comprises receiving beacons transmitted from communication nodes (106) in the monitored wireless communications networks (102), each beacon comprising a network identifier and a list of key IDs currently used in the respective network, and wherein said verifying comprises determining that the new key ID is not equal to any key ID in said list.

10. A method according to any of claims 1 -9, wherein the new key ID is distributed to communication nodes of a security group in the first wireless communications network (104).

1 1 . A method according to any of claims 1 -10, wherein the security key is associated to the first wireless communications network (104) or to an application supported by the first wireless communications network (104).

12. A method according to any of claims 1 -1 1 , wherein said generating of the new key ID comprises applying a key derivation function to the security key.

13. A provisioning node (500) arranged to handle key Identifiers, key IDs, used in wireless communication, wherein the provisioning node (500) is configured to:

- monitor (500A) usage of key IDs in multiple wireless communications networks, - generate (500B) a new key ID associated to a security key, for use in a first wireless communications network,

- verify (500C) the new key ID when the monitored usage of key IDs indicates that the new key ID is not already used in any of the monitored wireless

communications networks, and

- distribute (500D) the new key ID to communication nodes (106) within the first wireless communications network.

14. A provisioning node (500) according to claim 13, wherein the provisioning node (500) is configured to perform the monitoring by collecting key IDs from messages communicated in the monitored wireless communications networks, and to perform said verifying by determining that the new key ID is different from all key IDs already used in the monitored wireless communications networks according to said monitoring.

15. A provisioning node (500) according to claim 14, wherein the provisioning node (500) is configured to obtain the key IDs from a Protocol Data Unit, PDU, header attached to the messages.

16. A provisioning node (500) according to claim 14 or 15, wherein the provisioning node (500) is configured to repeat the monitoring and verifying at predefined intervals.

17. A provisioning node (500) according to claim 13, wherein when the new key ID is used in the first wireless communications network during a certain probing period, the provisioning node (500) is configured to perform said verifying based on whether any report of conflict between the new key ID and a key ID already used in the monitored wireless communications networks, has been received from the first wireless communications network during the probing period according to said monitoring.

18. A provisioning node (500) according to claim 17, wherein the provisioning node (500) is configured to initiate the probing period after the new key ID has been distributed to the communication nodes of the first wireless communications network.

19. A provisioning node (500) according to claim 17 or 18, wherein the provisioning node (500) is configured to repeat the probing period at least once to determine whether the new key ID needs to be changed.

20. A provisioning node (500) according to any of claims 17-19, wherein the provisioning node (500) is configured to verify the new key ID if the number of received reports of conflict is not above a threshold.

21 . A provisioning node (500) according to any of claims 13-20, wherein the provisioning node (500) is configured to perform said monitoring by receiving beacons transmitted from communication nodes in the monitored wireless communications networks, each beacon comprising a network identifier and a list of key IDs currently used in the respective network, and wherein said verifying comprises determining that the new key ID is not equal to any key ID in said list.

22. A provisioning node (500) according to any of claims 13-21 , wherein the provisioning node (500) is configured to distribute the new key ID to

communication nodes of a security group in the first wireless communications network.

23. A provisioning node (500) according to any of claims 13-22, wherein the security key is associated to the first wireless communications network or to an application supported by the first wireless communications network.

24. A provisioning node (500) according to any of claims 13-23, wherein the provisioning node (500) is configured to perform said generating by applying a key derivation function to the security key.

25. A method performed by a communication node (106, 502) for handling key Identifiers, key IDs, used in wireless communication in a wireless

communications network (102), the method comprising: - transmitting a beacon that can be received by a provisioning node (100, 500), the beacon comprising a network identifier and a list of key IDs currently used in the wireless communications network (102), thereby enabling the provisioning node (100, 500) to verify a new key ID when determining that the new key ID is not equal to any key ID in said list.

26. A method according to claim 25, wherein the communication node (106, 502) sends a report of conflict to the provisioning node (100) when detecting that the new key ID collides with a key ID already used in the wireless communications network (102).

27. A communication node (502) arranged to handle key Identifiers, key IDs, used in wireless communication in a wireless communications network, wherein the communication node (502) is configured to:

- transmit (502A) a beacon that can be received by a provisioning node (500), the beacon comprising a network identifier and a list of key IDs currently used in the wireless communications network, thereby enabling the provisioning node (500) to verify a new key ID when determining that the new key ID is not equal to any key ID in said list.

28. A communication node (502) according to claim 27, wherein the communication node is configured to send a report of conflict to the provisioning node (500) when detecting that the new key ID collides with a key ID already used in the wireless communications network.

29. A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any one of claims 1 -12 or the method according to any one of claims 25-26.

30. A carrier containing the computer program of claim 29, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.