Key updating method, related equipment and communication system

Abstract

The invention provides a key updating method, related equipment and a communication system, and relates to the technical field of wireless communication. The method comprises: a user equipment receiving an RRC reconfiguration signaling sent by a source node, the RRC reconfiguration signaling comprising candidate node key related information; according to the embodiment of the invention, the method supports the updating of the safety key under the continuous LTM switching, and effectively guarantees the safety of the user data in the switching process.

Description

Technical Field

[0001] This disclosure relates to the field of wireless communication technology, and in particular to a key update method, related equipment and communication system. Background Technology

[0002] In wireless communication systems, security keys are used to encrypt and decrypt communication data to prevent unauthorized access, eavesdropping, and malicious attacks. The primary reason for requiring security key updates during cell handover is to ensure the confidentiality and security of communications.

[0003] The existing LTM (L1 / L2 Triggered Mobility) mechanism does not support security key updates, and the retained security key is still used after the serving cell changes. Therefore, a new security key update scheme is needed to improve the security of user data during handover.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] This disclosure provides a key update method, related equipment, and communication system that overcomes, to some extent, the problems of insufficient confidentiality and security in existing LTM mechanisms.

[0006] As an example, the interpretation of the terminology in this disclosure is based on the definitions in the 3GPP specification protocol TS38 series.

[0007] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.

[0008] According to a first aspect of this disclosure, a key update method is provided, applied to a user equipment, the method comprising:

[0009] Receive RRC reconfiguration signaling sent by the source node. The RRC reconfiguration signaling includes candidate node key-related information.

[0010] In one embodiment of this disclosure, candidate node key information is used for security key updates in a mobility LTM triggered by layer 1 or layer 2.

[0011] In one embodiment of this disclosure, the candidate node key-related information includes the following:

[0012] Base station identifier or Next Generation Radio Access Network (NG-RAN) identifier;

[0013] An NCC list contains one or more NCC values.

[0014] In one embodiment of this disclosure, candidate node key-related information also includes an NCC counter.

[0015] According to a second aspect of this disclosure, a key update method is provided, applied to a source node, the method comprising:

[0016] Send RRC reconfiguration signaling to user equipment. The RRC reconfiguration signaling includes candidate node key information.

[0017] According to a third aspect of this disclosure, a key update method is provided, applied to a target node, the method comprising:

[0018] Receive the RRC reconfiguration complete message sent by the source node. The RRC reconfiguration complete message includes the NCC counter value.

[0019] The NCC counter value is used to indicate the NCC value used by the user equipment in this key deduction. The NCC value comes from the candidate node key information, which is sent to the user equipment by the source node through RRC reconfiguration signaling.

[0020] According to a fourth aspect of this disclosure, a key update method is provided for use in the Access and Mobility Management Function (AMF), the method comprising:

[0021] Send candidate node key information to the source node so that the source node can send the candidate node key information to the user equipment via RRC reconfiguration signaling.

[0022] According to a fifth aspect of this disclosure, a user equipment is provided, comprising:

[0023] The reconfiguration signaling receiving module is configured to receive RRC reconfiguration signaling sent by the source node. The RRC reconfiguration signaling includes candidate node key-related information.

[0024] According to a sixth aspect of this disclosure, a network device is provided, comprising:

[0025] The reconfiguration signaling sending module is configured to send RRC reconfiguration signaling to the user equipment. The RRC reconfiguration signaling includes candidate node key-related information.

[0026] According to a seventh aspect of this disclosure, a network device is provided, comprising:

[0027] The message receiving module is configured to receive the RRC reconfiguration completion message sent by the source node. The RRC reconfiguration completion message includes the NCC counter value.

[0028] The NCC counter value is used to indicate the NCC value used by the user equipment in this key deduction. The NCC value comes from the candidate node key information, which is sent to the user equipment by the source node through RRC reconfiguration signaling.

[0029] According to the eighth aspect of this disclosure, a mobility management function is provided, comprising:

[0030] The information sending module is configured to send candidate node key-related information to the source node, so that the source node can send the candidate node key-related information to the user equipment via RRC reconfiguration signaling.

[0031] According to a ninth aspect of this disclosure, a communication system is provided, including a network device as described in the fifth aspect, a network device as described in the sixth aspect, a network device as described in the seventh aspect, and a mobility management function as described in the eighth aspect.

[0032] According to a tenth aspect of this disclosure, an electronic device is provided, comprising: a memory for storing instructions; and a processor for calling the instructions stored in the memory to implement the above-described key update method.

[0033] According to the eleventh aspect of this disclosure, a computer-readable storage medium is provided that stores computer instructions thereon, which, when executed by a processor, implement the above-described key update method.

[0034] According to the twelfth aspect of this disclosure, a computer program product is provided, which stores instructions that, when executed by a computer, cause the computer to perform the key update method described above.

[0035] According to the thirteenth aspect of this disclosure, a chip is provided, including at least one processor and an interface;

[0036] An interface is used to provide program instructions or data to at least one processor;

[0037] At least one processor is used to execute program instructions to implement the key update method described above.

[0038] The key update method, related devices, and communication system provided in this disclosure involve the source node sending RRC reconfiguration signaling to the user equipment. The RRC reconfiguration signaling includes candidate node key-related information, which is used for security key updates in LTM triggered by Layer 1 or Layer 2. This scheme supports security key updates under continuous conditional LTM handover, effectively ensuring the security of user data during the handover process.

[0039] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0040] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0041] Obviously, the accompanying drawings described below are merely some embodiments of this disclosure. Those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0042] Figure 1 This diagram illustrates a key update method according to an embodiment of the present disclosure.

[0043] Figure 2 This illustrates a key chain model during switching in an embodiment of this disclosure.

[0044] Figure 3 This diagram illustrates another key update method flowchart in an embodiment of this disclosure;

[0045] Figure 4 This illustration shows a flowchart of yet another key update method in an embodiment of the present disclosure;

[0046] Figure 5 This diagram illustrates a flowchart of yet another key update method in an embodiment of this disclosure;

[0047] Figure 6 This diagram illustrates a key update method applied to a user equipment in an embodiment of this disclosure.

[0048] Figure 7 This diagram illustrates a key update method applied to the source node in an embodiment of this disclosure.

[0049] Figure 8 This diagram illustrates a key update method applied to a target node in an embodiment of this disclosure.

[0050] Figure 9 This diagram illustrates a key update method applied to the AMF in an embodiment of this disclosure.

[0051] Figure 10 This diagram illustrates a user equipment according to an embodiment of the present disclosure;

[0052] Figure 11 This diagram illustrates a network device according to an embodiment of the present disclosure;

[0053] Figure 12 This diagram illustrates a network device according to an embodiment of the present disclosure;

[0054] Figure 13 This diagram illustrates a mobility management function according to an embodiment of the present disclosure.

[0055] Figure 14 A structural block diagram of an electronic device according to an embodiment of the present disclosure is shown. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. The components of the embodiments of this disclosure described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this disclosure provided in the accompanying drawings is not intended to limit the scope of the claimed disclosure, but merely represents selected embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0057] Traditional serving cell handover is based on L3 measurement and triggered by RRC signaling. The UE needs to perform a complete cell reconfiguration and L1 / L2 reconstruction process, which leads to significant handover latency and signaling overhead. The core idea of ​​the LTM (L1 / L2 TriggeredMobility) mechanism is to trigger serving cell handover through L1 / L2 signaling to achieve the goals of low latency, low overhead, and low data interruption time.

[0058] The core idea of ​​the LTM mechanism is based on a pre-configured set of candidate cells. LTM includes two triggering schemes: Normal LTM and Conditional LTM. In Normal LTM, the terminal performs L1 measurements and reports the results. The network then triggers a handover to the serving cell via L1 / L2 signaling. In Conditional LTM, the terminal evaluates candidate cells based on the pre-configured settings. When a candidate cell meets the triggering conditions, the terminal directly initiates access to that candidate cell, completing the handover to the target cell.

[0059] Another feature of the LTM mechanism is its support for continuous cell handover, meaning that the terminal can perform multiple consecutive cell handovers from the candidate cell set configured by the network (the handover can be triggered by the network using Normal LTM, or by the terminal itself using Conditional LTM). In traditional L3 handover, after the terminal completes a cell handover, both the network and the terminal need to release the corresponding handover configuration until the next handover is required, at which point the network configures candidate / target cell information for the terminal.

[0060] In wireless communication systems, security keys are used to encrypt and decrypt communication data to prevent unauthorized access, eavesdropping, and malicious attacks. The primary reason for requiring security key updates during cell handover is to ensure the confidentiality and security of communication. The NR system employs a layered approach to security management, separating Access Stratum (AS) security from Non-Access Stratum (NAS) security. AS security is the security between the UE and the base station. AS security mechanisms ensure that control plane RRC messages between the UE and the base station are encrypted and protected for integrity using AS keys, while also guaranteeing that user plane messages are encrypted using AS keys. NAS security is the security between the UE and the Access and Mobility Function (AMF). Its main responsibility is to ensure that control plane NAS messages between the UE and the AMF are encrypted and protected for integrity using NAS keys.

[0061] As described in the background section, existing LTM mechanisms do not support security key updates, and the retained security key is still used even after the serving cell changes. The inventors have found that this approach currently limits LTM handover to Intra-CU scenarios (i.e., handover between cells within the same base station can use the LTM scheme). Considering that the LTM mechanism needs to support inter-CU handover scenarios, a security key update mechanism within the LTM mechanism needs to be considered. Based on this, this disclosure proposes a security key update scheme for the Conditional LTM mechanism in inter-CU scenarios to support security key updates under continuous conditional LTM handover, effectively ensuring the security of user data during handover.

[0062] The NR system supports frequencies ranging from low to high frequencies. As the frequency increases, cell coverage decreases, leading to more frequent cell handovers for users. 3GPP introduced the LTM (L1 / L2 mobility) mechanism to achieve low-latency handover. Currently, LTM supports continuous handover mechanisms, meaning the network is configured once, and the terminal executes the LTM process multiple times until it receives a new mobility configuration (such as other handover type parameter configurations). In inter-CU scenarios, synchronous updating of security keys is a critical issue that must be addressed to achieve continuous conditional LTM handover; currently, there is no solution to this problem.

[0063] Compared to traditional L3-based handover methods, the LTM mechanism offers lower handover latency and shorter measurement and trigger times, making it particularly suitable for high-frequency scenarios and meeting the high-bandwidth, low-latency requirements of emerging applications (such as immersive XR). Considering that low-frequency resources are nearing saturation and wireless networks are evolving towards higher frequencies, the LTM mechanism is expected to be widely commercialized for high-frequency scenarios such as millimeter waves.

[0064] The Inter-CU LTM mechanism is one of the potential research areas of the 3GPP R19 mobility enhancement project. The embodiments disclosed herein design a secure key update process for application conditional LTM in the inter-CU scenario, which effectively ensures the secure and reliable transmission of data by the terminal during the conditional LTM handover process.

[0065] The following detailed description of this exemplary implementation method is provided in conjunction with the accompanying drawings and embodiments.

[0066] It is understood that the application scenario of the key update scheme in this disclosure is that the user equipment selects the target node to be switched from the candidate nodes and switches from the source node to the target node. The aforementioned "node" can be a base station in the communication system or a base station central unit (CU).

[0067] Figure 1 This diagram illustrates a key update method flowchart according to an embodiment of the present disclosure, such as... Figure 1 As shown, the key update method provided in this embodiment includes step S101.

[0068] In S101, the user equipment receives the RRC reconfiguration signaling sent by the source node. The RRC reconfiguration signaling includes candidate node key-related information.

[0069] In some embodiments, candidate node key-related information is used for key updates.

[0070] In some embodiments, candidate node key information is used for security key updates in mobility LTM triggered by layer 1 or layer 2.

[0071] In some embodiments, candidate node key-related information may be a candidate node and next-hop link count NCC mapping list.

[0072] In some embodiments, candidate node key related information includes the following: base station identifier or Next Generation Radio Access Network (NG-RAN) identifier; NCC list, which contains one or more NCC values.

[0073] In some embodiments, candidate node key-related information may also include an NCC counter.

[0074] In this embodiment of the disclosure, after the source node determines the candidate node set, it sends NGAP signaling to the AMF, which includes a Candidate gNB ID List. The AMF generates an NCC List for each gNB based on the Candidate gNB ID List and feeds it back to the source node via NGAP. The source node generates an NCC Mapping List and reconfigures the sending terminal via RRC. The cell structure of the NCC Mapping List is shown in the table below:

[0075] Table 1

[0076] NCC Mapping List Cell Structure Meaning of information element >NCC Mapping List NCC and gNB mapping relationship list >>gNB ID / NG-RAN node ID Base station representation or NG-RAN node identifier >>>NCC Value List Provide a list of NCC values ​​for per-gNB, containing one or more NCC values. >>>NCC Counter An NCC counter is used to record which NCC value is used.

[0077] In some embodiments, the key update method may further include: the user equipment selecting a target cell; the user equipment obtaining the NCC value corresponding to the target node to which the target cell belongs based on candidate node key information; and the user equipment deducing the security key of the target node to which the target cell belongs based on the NCC value.

[0078] It should be noted that if the candidate node key information includes an NCC counter, the user equipment (UE) obtains the NCC value corresponding to the target node of the target cell based on the candidate node key information, and then deduces the security key of the target node of the target cell based on the NCC value. If the candidate node key information does not include an NCC counter, the UE and network can use the first unused NCC value in the NCC list corresponding to the target node to deduce the key.

[0079] In the above embodiments, the target cell can be selected based on the reception quality of the reference signal of the candidate cell and the execution conditions; or, the target cell can be determined based on the first signaling sent by the source node, which carries relevant information about the target cell.

[0080] In this embodiment of the disclosure, by constructing and transmitting candidate node key-related information (e.g., NCC MappingList), the parameters of the security key can be synchronized between the UE and the network in a timely manner, and an NCC counter is introduced to complete the synchronization of the user equipment and network-side keys. By applying the scheme of this embodiment of the disclosure, in the conditional LTM cell handover process, the security keys of the terminal and the target base station can be synchronized in a timely manner after each cell handover, effectively ensuring the security of user data and effectively expanding the application scenarios of LTM.

[0081] In some embodiments, the key update method may further include: the user equipment sending an RRC reconfiguration completion message to the target node, the RRC reconfiguration completion message including the NCC counter value used in this key deduction, the NCC counter value being used to assist the network side in achieving secure key synchronization with the user equipment.

[0082] In some embodiments, after the user equipment sends an RRC reconfiguration completion message to the target node, the target node detects the user equipment access and sends a path handover request signaling to the Access and Mobility Management Function (AMF). The path handover request signaling includes the received NCC counter value. The AMF determines the NCC and next-hop NH for key deduction based on the NCC counter value and sends a path handover request feedback signaling to the target node. The path handover request feedback signaling includes the NCC and NH for key deduction. The target node performs key deduction based on the NCC and NH to obtain the security key.

[0083] In this embodiment, the NCC Counter is used to complete the key synchronization between the UE and the network side:

[0084] RRC reconfiguration completion signaling enhancement (UE->target gNB): After determining the target base station, the UE selects the NCC based on the NCC MappingList information element and sends the corresponding NCC Counter to the target node through RRC reconfiguration completion signaling;

[0085] Enhanced Path Switching Request Signalling (Target gNB->AMF): The target node receives the NCC counter value from the RRC reconfiguration signaling via path switching signaling and sends it to the AMF. The AMF determines the NCC and NH for key deduction based on the NCC counter value and sends a path switching request feedback signaling to the target node, which includes {NH, NCC}. The target node performs key deduction based on the received {NH, NCC} to obtain the security key.

[0086] In some embodiments, candidate node key-related information is obtained by the source node from the AMF.

[0087] In some embodiments, the AMF receives a candidate node list (Candidate gNB IDList) sent by the source node, generates one or more NCC values ​​for each candidate node to form an NCC list, and obtains candidate node key-related information.

[0088] In some embodiments, the key update method may further include: the user equipment performing L3 measurement and reporting the L3 measurement report to the source node, so that the source node decides to configure LTM based on the L3 measurement report, sending a handover request signaling to one or more candidate nodes, the handover request signaling including information related to the requested LTM candidate cells, the candidate nodes performing access control, and if they accept the LTM request, sending a handover request feedback signaling to the source node, and the source node determining the candidate cell set and the corresponding candidate nodes.

[0089] like Figure 2As shown, the security key derivation process in the NR system is divided into horizontal key derivation and vertical key derivation, and the specific calculation formula is as follows:

[0090] KNG-RetPCI,ARFCN-DL / EARFCN-DL)(1)

[0091] K NG-RAN* =KDF(NH,target PCI,ARFCN-DL / EARFCN-DL) (2)

[0092] NHNCC=KDF(KAMF,NHNCC-1) (3)

[0093] In the formula, NH is the base key for vertical key derivation, calculated by the terminal and AMF during handover, and then passed to the base station by the AMF; NCC represents the level of vertical derivation; Target PCI is the physical cell identity of the target cell; ARFCN-DL / EARFCN-DL are the downlink frequency points of the target base station. KDF (Key Derivation Function) is a one-way key derivation function.

[0094] Equation (1) is for horizontal key derivation, i.e., KNG-RAN* is derived from the current key KgNB. On the source base station side, it is applicable when: (1) the source base station has no available NH key; (2) {NH, NCC} has not arrived at the source base station before the handover; (3) the NCC in the source base station is greater than or equal to the NCC transmitted from the AMF. Equation (2) is for vertical key derivation, i.e., KNG-RAN* is derived from NH. It is applicable when the NCC in the source base station is less than the NCC transmitted from the AMF. The source base station and the terminal use KNG-RAN* as KgNB*. Equation (3) is for the derivation of NH. After key derivation occurs on the base station side, the NCC is transmitted to the terminal through the handover command. The terminal compares the received NCC with its own stored NCC. If they are equal, horizontal key derivation is used; otherwise, vertical key derivation is used.

[0095] In a wireless communication system, the core network is responsible for generating a key K_AMF to protect the NAS, a key KgNB to protect the AS, and an NH key to ensure forward security during Xn handover. These keys are then sent to the base station via the AMF. When handover is required, the AMF transmits the NH key to the base station. The UE uses a permanent key K stored in its SIM or USIM card to synchronously generate an identical set of keys, thereby ensuring the security and integrity of the terminal when moving within the wireless network.

[0096] The biggest differences between Conditional LTM (hereinafter referred to as C-LTM) and traditional L3 handover are reflected in the following two points:

[0097] C-LTM cell handover is triggered by the terminal, while traditional L3 handover is triggered by the network. In traditional L3 handover, the network selects the key parameter NCC and sends it to the UE via a Hanover Command message, thus achieving key synchronization between the UE and the network. Under the C-LTM mechanism, since the terminal autonomously triggers the handover based on pre-configured information, the target cell is selected by the UE itself, and the network does not need to issue RRC signaling. Therefore, key synchronization cannot reuse the traditional L3 handover procedure.

[0098] C-LTM supports continuous handover, meaning that after receiving an RRC reconfiguration message containing the C-LTM configuration, the terminal can perform multiple handovers within the candidate cell set based on this C-LTM configuration until it receives a new instruction from the network (such as releasing the C-LTM configuration). Therefore, the key synchronization process design must consider the continuous handover characteristics of C-LTM, and the designed scheme must ensure that the UE and network-side keys can be synchronized even under multiple handovers.

[0099] In summary, this disclosure presents a method where the AMF pre-configures an NCC List for candidate nodes, constructs an NCC mapping list between candidate nodes and NCCs, and transmits this list to the UE during the C-LTM preparation phase. This ensures that security key parameters can be synchronized between the UE and the network in a timely manner, and an NCC Counter is introduced to synchronize the keys between the UE and the network. By applying this disclosure, during the Conditional LTM cell handover process, the security keys of the terminal and the target base station can be synchronized promptly after each cell handover, effectively ensuring the security of user data.

[0100] Figure 3 This diagram illustrates a key update method flowchart according to an embodiment of the present disclosure, such as... Figure 3 As shown, the key update method provided in this embodiment includes steps S301-S312.

[0101] In S301, AMF generates an NCC list for each candidate node and feeds back the NCC Mapping List to the source node.

[0102] In S302, the source node (such as the Source gNB) sends RRC reconfiguration signaling to the UE, which includes the NCCMapping List.

[0103] In S303, the user equipment (UE) performs L1 measurements and reports the L1 measurement report to the source node.

[0104] In S304, the source node selects the target cell based on the L1 measurement report.

[0105] In S305, the source node sends an LTM Cell Switch Command to the UE, which includes candidate cell information (such as candidate cell identifier or index).

[0106] In S306, the UE selects the NCC value to be used for this simulation key based on the NCC Mapping List, and calculates the key of the target node (Target gNB) based on the NCC value.

[0107] In S307, the UE sends an RRC reconfiguration completion message to the target node, which includes the NCC counter value used in this key deduction.

[0108] In S308, the target cell detection terminal under the target node is accessed.

[0109] In S309, the target node sends a path switching request signaling to the AMF, which includes the NCC counter value received from the RRC reconfiguration signaling.

[0110] In S310, the AMF determines the NCC and NH of the key derivation based on the NCC counter value, and sends a path switching request feedback signaling to the target node, which includes {NH, NCC}.

[0111] In S311, the target node performs key deduction based on the received {NH, NCC} to obtain the security key.

[0112] In S312, the derived security key is synchronized to the source node and other candidate nodes.

[0113] Figure 4 This diagram illustrates a key update method flowchart according to an embodiment of the present disclosure, such as... Figure 4 As shown, the key update method provided in this embodiment includes steps S401-S416.

[0114] In S401, the UE performs L3 measurements and reports the L3 measurement to the source node.

[0115] In S402, the source node determines the configuration of Conditional LTM based on the L3 measurement report.

[0116] In S403, the source node sends a handover request signaling to one or more candidate nodes, which includes information about the requested LTM candidate cell.

[0117] In S404, the candidate node performs access control. If it accepts the LTM request, it sends a handover request feedback signaling to the source node.

[0118] In S405, the source node determines the final set of candidate cells and the corresponding candidate nodes.

[0119] In S406, the source node sends the candidate node list (Candidate gNB ID List) to the AMF.

[0120] In S407, AMF generates an NCC list for each candidate node and feeds back the NCC Mapping List to the source node.

[0121] In S408, the source node generates LTM configuration information (LTM-config), which includes the NCC Mapping List.

[0122] In S409, the source node sends RRC reconfiguration signaling to the UE, which includes the NCC Mapping List.

[0123] In S410, the UE evaluates the status of candidate cells and selects the target cell.

[0124] In S411, the UE selects the NCC value to be used for this simulation key based on the NCC Mapping List, and calculates the key of the target node based on the NCC value.

[0125] In S412, the UE sends an RRC reconfiguration completion message to the target node, which includes the NCC counter value used in this key deduction.

[0126] In S413, the target cell detection terminal under the target node is connected.

[0127] In S414, the target node sends a path switching request signaling to the AMF, which includes the NCC counter value received from the RRC reconfiguration signaling.

[0128] In S415, the AMF determines the NCC and NH of the key derivation based on the NCC counter value and sends a path switching request feedback signaling to the target node, which includes {NH, NCC}.

[0129] In S416, the target node performs key deduction based on the received {NH, NCC} to obtain the security key.

[0130] At this point, the synchronization and update of the UE and network security key are complete.

[0131] It should be noted that, Figure 4This embodiment describes the security key update signaling interaction process under the Conditional LTM mechanism. The UE accesses the source node through the source cell, and the security keys between the terminal and the source node are synchronized. The terminal stores KAMF, the current key KgNB, NH, and NCC. Communication data between the terminal and the source node is encrypted and decrypted using the security key, ensuring the security of data transmission.

[0132] Figure 5 This diagram illustrates a key update method flowchart according to an embodiment of the present disclosure, such as... Figure 5 As shown, the key update method provided in this embodiment includes steps S501-S518.

[0133] In S501, the UE performs L3 measurements and reports the L3 measurement to the source node.

[0134] In S502, the source node determines the LTM configuration based on the L3 measurement report.

[0135] In S503, the source node sends a handover request signaling to one or more candidate nodes, which includes information about the requested LTM candidate cells.

[0136] In S504, the candidate node performs access control. If it accepts the LTM request, it sends a handover request feedback signaling to the source node.

[0137] In S505, the source node determines the final set of candidate cells and the corresponding candidate nodes.

[0138] In S506, the source node sends the candidate node list (Candidate gNB ID List) to the AMF.

[0139] In S507, AMF generates a set of NCC lists for each candidate node and feeds back the NCC Mapping List to the source node.

[0140] In S508, the source node generates LTM configuration information (LTM-config), which includes the NCC Mapping List.

[0141] In S509, the source node sends RRC reconfiguration signaling to the UE, which includes the NCC Mapping List.

[0142] In S510, the UE performs L1 measurements and reports L1 measurement data.

[0143] In S511, the source node selects the target cell based on the L1 measurement report and decides to trigger LTM handover.

[0144] In S512, the source node sends an LTM Cell Switch Command message to the UE, which contains candidate cell information (such as candidate cell identifier or index).

[0145] In S513, the UE selects the NCC value to be used for this simulation key based on the NCC Mapping List, and calculates the key of the target node based on the NCC value.

[0146] In S514, the UE sends an RRC reconfiguration completion message to the target node, which includes the NCC counter value used in this key deduction.

[0147] In S515, the target cell detection terminal under the target node is connected.

[0148] In S516, the target node sends a path switching request signaling to the AMF, which includes the NCC counter value received from the RRC reconfiguration signaling.

[0149] In S517, the AMF determines the NCC and NH of the key derivation based on the NCC counter value and sends a path switching request feedback signaling to the target node, which includes {NH, NCC}.

[0150] In S518, the target node performs key deduction based on the received {NH, NCC} to obtain the security key.

[0151] At this point, the synchronization and update of the UE and network security key are complete.

[0152] It should be noted that, Figure 5 This embodiment describes the security key update signaling interaction process under the Normal LTM mechanism. The UE accesses the source node through the source cell, and the security key is synchronized between the terminal and the source node. The terminal stores KAMF, the current key KgNB, NH, and NCC. Communication data between the terminal and the source node is encrypted and decrypted using the security key, ensuring the security of data transmission.

[0153] Figure 6 This disclosure illustrates a key update method in an embodiment, applied to a user equipment, such as... Figure 6 As shown, the key update method provided in this embodiment includes step S601.

[0154] In S601, the RRC reconfiguration signaling sent by the source node is received. The RRC reconfiguration signaling includes candidate node key-related information.

[0155] In some embodiments, candidate node key information is used for security key updates in mobility LTM triggered by layer 1 or layer 2.

[0156] In some embodiments, candidate node key related information includes the following: base station identifier or Next Generation Radio Access Network (NG-RAN) identifier; NCC list, which contains one or more NCC values.

[0157] In some embodiments, candidate node key-related information may also include an NCC counter.

[0158] Figure 7 This disclosure illustrates a key update method applied to a source node, such as... Figure 7 As shown, the key update method provided in this embodiment includes step S701.

[0159] In S701, an RRC reconfiguration signaling message is sent to the user equipment. The RRC reconfiguration signaling message includes candidate node key-related information.

[0160] In some embodiments, the method may further include: sending a list of candidate nodes to the AMF so that the AMF generates one or more NCC values ​​for each candidate node to form an NCC list and obtain candidate node key-related information; and obtaining candidate node key-related information from the AMF.

[0161] Figure 8 This diagram illustrates a key update method flowchart in an embodiment of the present disclosure, applied to a target node, such as... Figure 8 As shown, the key update method provided in this embodiment includes step S801.

[0162] In S801, the RRC reconfiguration completion message sent by the source node is received. The RRC reconfiguration completion message includes the NCC counter value. The NCC counter value is used to indicate the NCC value used by the user equipment in this key deduction. The NCC value comes from the candidate node key-related information, which is sent to the user equipment by the source node through RRC reconfiguration signaling.

[0163] Figure 9 This disclosure illustrates a key update method applied to the Access and Mobility Management Function (AMF), such as... Figure 9 As shown, the key update method provided in this embodiment includes step S901.

[0164] In S901, candidate node key information is sent to the source node so that the source node can send the candidate node key information to the user equipment via RRC reconfiguration signaling.

[0165] In embodiments of this disclosure, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0166] In this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0167] Furthermore, although the steps of the method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result.

[0168] In some embodiments, certain steps may be omitted, multiple steps may be combined into one step for execution, and / or one step may be broken down into multiple steps for execution.

[0169] Based on the same inventive concept, this disclosure also provides a user equipment, such as... Figure 10 As shown, the user equipment includes a reconfiguration signaling receiving module 1001.

[0170] The reconfiguration signaling receiving module 1001 is configured to receive RRC reconfiguration signaling sent by the source node. The RRC reconfiguration signaling includes candidate node key-related information.

[0171] In some embodiments, candidate node key information is used for security key updates in mobility LTM triggered by layer 1 or layer 2.

[0172] In some embodiments, the user equipment further includes a key deduction module.

[0173] The key deduction module is configured to select a target cell; obtain the NCC value corresponding to the target node to which the target cell belongs based on the candidate node key information; and deduce the security key of the target node to which the target cell belongs based on the NCC value.

[0174] In some embodiments, the user equipment further includes a reconfiguration completion message sending module.

[0175] The reconfiguration completion message sending module is configured to send an RRC reconfiguration completion message to the target node. The RRC reconfiguration completion message includes the NCC counter value used in this key deduction. The NCC counter value is used to assist the network side in realizing the security key synchronization with the user equipment.

[0176] In some embodiments, candidate node key-related information is obtained by the source node from the AMF.

[0177] In some embodiments, the AMF receives a list of candidate nodes sent by the source node, generates one or more NCC values ​​for each candidate node to form an NCC list, and obtains candidate node key-related information.

[0178] In some embodiments, the user equipment further includes an L3 measurement reporting module.

[0179] The L3 measurement reporting module is configured to perform L3 measurements and report L3 measurement reports to the source node, so that the source node can decide to configure LTM based on the L3 measurement reports and send handover request signaling to one or more candidate nodes. The handover request signaling includes information related to the requested LTM candidate cells. The candidate nodes perform access control. If they accept the LTM request, they send a handover request feedback signaling back to the source node. The source node determines the candidate cell set and the corresponding candidate nodes.

[0180] In some embodiments, candidate node key-related information includes the following:

[0181] Base station identifier or Next Generation Radio Access Network (NG-RAN) identifier;

[0182] An NCC list contains one or more NCC values.

[0183] In some embodiments, candidate node key-related information may also include an NCC counter.

[0184] Based on the same inventive concept, this disclosure also provides a network device, such as... Figure 11 As shown, the network device 1100 includes a reconfiguration signaling sending module 1101.

[0185] The reconfiguration signaling sending module 1101 is configured to send RRC reconfiguration signaling to the user equipment. The RRC reconfiguration signaling includes candidate node key-related information.

[0186] In some embodiments, the network device 1100 further includes a candidate node list sending module and a key information acquisition module.

[0187] The candidate node list sending module is configured to send the candidate node list to the AMF, so that the AMF generates one or more NCC values ​​for each candidate node, forming an NCC list, and obtains candidate node key-related information.

[0188] The key information acquisition module is configured to obtain candidate node key-related information from the AMF.

[0189] In some embodiments, the network device 1100 further includes a report receiving module, a signaling sending module, and a candidate node determination module.

[0190] The report receiving module is configured to receive L3 measurement reports sent by user equipment;

[0191] The signaling sending module is configured to determine the LTM configuration based on the L3 measurement report, and send handover request signaling to one or more candidate nodes. The handover request signaling includes information related to the requested LTM candidate cell, so that one or more candidate nodes can perform access control. If the LTM request is accepted, the module sends a handover request feedback signaling back to the source node.

[0192] The candidate node determination module is configured to determine the set of candidate cells and the corresponding candidate nodes based on the received handover request feedback signaling.

[0193] Based on the same inventive concept, this disclosure also provides a network device, such as... Figure 12 As shown, the network device 1200 includes a message receiving module 1101.

[0194] The message receiving module is configured to receive the RRC reconfiguration completion message sent by the source node. The RRC reconfiguration completion message includes the NCC counter value.

[0195] The NCC counter value is used to indicate the NCC value used by the user equipment in this key deduction. The NCC value comes from the candidate node key information, which is sent to the user equipment by the source node through RRC reconfiguration signaling.

[0196] In some embodiments, the network device 1200 further includes a switching request sending module and a security key deduction module.

[0197] The switching request sending module is configured to send path switching request signaling to the AMF. The path switching request signaling includes the received NCC counter value, so that the AMF can determine the NCC and next hop NH based on the NCC counter value, and feed back path switching request feedback signaling to the target node. The path switching request feedback signaling includes the NCC and NH of the key deduction.

[0198] The security key deduction module is configured to perform key deduction based on NCC and NH to obtain the security key.

[0199] In some embodiments, the network device 1200 further includes a signaling receiving module and a feedback module.

[0200] The signaling receiving module is configured to receive handover request signaling sent by the source node;

[0201] The feedback module is configured to accept the LTM request and send a handover request feedback signaling to the source node, so that the source node can determine the candidate cell set and the corresponding candidate node based on the received handover request feedback signaling.

[0202] Based on the same inventive concept, this disclosure also provides a mobility management function, such as... Figure 13 As shown, the mobility management function includes an information sending module 1301.

[0203] The information sending module 1301 is configured to send candidate node key-related information to the source node, so that the source node can send the candidate node key-related information to the user equipment via RRC reconfiguration signaling.

[0204] In some embodiments, the mobility management function further includes a node list sending module.

[0205] The node list sending module is configured to receive the candidate node list sent by the source node, generate one or more NCC values ​​for each candidate node to form an NCC list, and obtain candidate node key-related information.

[0206] Based on the same inventive concept, this disclosure also provides a communication system, which includes a user equipment, a network device, and a mobility management function entity. The user equipment can be used to execute the steps performed by the user equipment in the above-described key update method embodiments; the network device can be used to execute the steps performed by the source node, candidate node, and target node in the above-described key update method embodiments; and the mobility management function entity can be used to execute the steps performed by the mobility management function entity in the above-described key update method embodiments.

[0207] The concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different devices, modules or units, and are not used to define the order of functions performed by these devices, modules or units or their interdependencies.

[0208] It should be noted that although several modules or units of the device used for action execution are mentioned in the detailed description above, this division is not mandatory.

[0209] In fact, according to embodiments of this disclosure, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units.

[0210] Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0211] The following reference Figure 14 This describes the electronic device provided in the embodiments of this disclosure. Figure 14 The electronic device 1400 shown is merely an example and should not be construed as limiting the functionality and scope of use of the embodiments disclosed herein.

[0212] Figure 14 This diagram illustrates the architecture of an electronic device 1400 provided in an embodiment of the present invention. Figure 14 As shown, the electronic device 1400 includes, but is not limited to, at least one processor 1410 and at least one memory 1420.

[0213] Memory 1420 is used to store instructions.

[0214] In some embodiments, memory 1420 may include a readable medium in the form of volatile memory cells, such as random access memory (RAM) 14201 and / or cache memory 14202, and may further include read-only memory (ROM) 14203.

[0215] In some embodiments, the memory 1420 may also include a program / utility 14204 having a set (at least one) of program modules 14205, such program modules 14205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each or some combination of these examples may include an implementation of a network environment.

[0216] In some embodiments, memory 1420 may store an operating system. This operating system may be a real-time operating system (RTX), such as Linux, UNIX, Windows, or OS X.

[0217] In some embodiments, the memory 1420 may also store data.

[0218] As an example, processor 1410 can read data stored in memory 1420, which may be stored at the same memory address as the instruction, or the data may be stored at a different memory address than the instruction.

[0219] Processor 1410 is configured to invoke instructions stored in memory 1420 to implement the steps described in the "Exemplary Methods" section above, according to various exemplary embodiments of this disclosure. For example, processor 1410 may execute the steps of the above method embodiments.

[0220] It should be noted that the processor 1410 described above can be a general-purpose processor or a special-purpose processor. The processor 1410 may include one or more processing cores, and the processor 1410 executes various functional applications and data processing by running instructions.

[0221] In some embodiments, processor 1410 may include a central processing unit (CPU) and / or a baseband processor.

[0222] In some embodiments, the processor 1410 may determine an instruction based on the priority identifier and / or function category information carried in each control instruction.

[0223] In this disclosure, the processor 1410 and the memory 1420 can be configured separately or integrated together.

[0224] As an example, the processor 1410 and memory 1420 can be integrated on a single board or a system on chip (SOC).

[0225] like Figure 14 As shown, electronic device 1400 is presented in the form of a general-purpose computing device. Electronic device 1400 may also include bus 1430.

[0226] Bus 1430 can represent one or more of several types of bus structures, including a memory bus or memory controller, peripheral bus, graphics acceleration port, processor, or a local bus using any of the various bus structures.

[0227] Electronic device 1400 can also communicate with one or more external devices 1440 (e.g., keyboard, pointing device, Bluetooth device, etc.), and with one or more devices that enable a user to interact with electronic device 1400, and / or with any device that enables electronic device 1400 to communicate with one or more other computing devices (e.g., router, modem, etc.). Such communication can be performed through input / output (I / O) interface 1450.

[0228] Furthermore, the electronic device 1400 can also communicate with one or more networks (such as local area networks (LANs), wide area networks (WANs), and / or public networks, such as the Internet) via the network adapter 1460.

[0229] like Figure 14 As shown, network adapter 1460 communicates with other modules of electronic device 1400 via bus 1430.

[0230] It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the electronic device 1400, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0231] It is understood that the structure illustrated in the embodiments of this disclosure does not constitute a specific limitation on the electronic device 1400. In other embodiments of this disclosure, the electronic device 1400 may include more than Figure 14 This may involve more or fewer components, or combining certain components, or splitting certain components, or different component arrangements. Figure 14 The components shown can be implemented in hardware, software, or a combination of both.

[0232] This disclosure also provides a computer-readable storage medium storing computer instructions thereon, which, when executed by a processor, implement the key update method described in the above method embodiments.

[0233] In this embodiment of the disclosure, the computer-readable storage medium is a computer instruction that can be sent, propagated, or transmitted for use by or in conjunction with an instruction execution system, apparatus, or device.

[0234] As an example, a computer-readable storage medium is a non-volatile storage medium.

[0235] In some embodiments, more specific examples of computer-readable storage media in this disclosure may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, USB flash drives, portable hard drives, or any suitable combination of the foregoing.

[0236] In this embodiment of the disclosure, the computer-readable storage medium may include data signals propagated in baseband or as part of a carrier wave, wherein computer instructions (readable program code) are carried.

[0237] The transmitted data signal can take many forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof.

[0238] In some examples, computational instructions contained on a computer-readable storage medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination thereof.

[0239] This disclosure also provides a computer program product that stores instructions that, when executed by a computer, cause the computer to implement the key update method described in the above method embodiments.

[0240] The aforementioned instructions can be program code. In practice, the program code can be written using any combination of one or more programming languages.

[0241] Programming languages ​​include object-oriented programming languages—such as Java and C++—as well as conventional procedural programming languages—such as the "C" language or similar programming languages.

[0242] The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0243] In cases involving remote computing devices, the remote computing devices can be connected to user computing devices via any type of network, including local area networks (LANs) or wide area networks (WANs), or they can be connected to external computing devices (e.g., via the Internet using an Internet service provider).

[0244] This disclosure also provides a chip, including at least one processor and an interface;

[0245] An interface is used to provide program instructions or data to at least one processor;

[0246] At least one processor is used to execute program instructions to implement the key update method described in the above method embodiments.

[0247] In some embodiments, the chip may further include a memory for storing program instructions and data, the memory being located within or outside the processor.

[0248] Those skilled in the art will understand that all or part of the steps of the above embodiments can be specifically implemented in the following forms: a completely hardware implementation, a completely software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which can be collectively referred to as "circuit", "module" or "system".

[0249] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein.

[0250] This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A key update method, characterized in that, Applied to user equipment, the method includes: Receive RRC reconfiguration signaling sent by the source node, the RRC reconfiguration signaling including candidate node key related information.

2. The method according to claim 1, characterized in that, The candidate node key information is used for security key updates in mobility LTM triggered by layer 1 or layer 2.

3. The method according to claim 1, characterized in that, The method further includes: Select the target community; Based on the candidate node key information, the NCC value corresponding to the target node to which the target cell belongs is obtained; Based on the NCC value, the security key of the target node to which the target cell belongs is deduced.

4. The method according to claim 3, characterized in that, The selected target cell includes: The target cell is selected based on the reference signal reception quality and execution conditions of the candidate cells; Alternatively, receive a first signaling message sent by the source node, the first signaling message carrying target cell information, and determine the target cell based on the target cell information.

5. The method according to claim 3, characterized in that, The method further includes: The target node is fed back an RRC reconfiguration completion message. The RRC reconfiguration completion message includes the NCC counter value used in this key deduction. The NCC counter value is used to assist the network side in realizing the security key synchronization with the user equipment.

6. The method according to claim 5, characterized in that, After the user equipment sends an RRC reconfiguration completion message to the target node, the target node detects the user equipment access and sends a path switching request signaling to the Access and Mobility Management Function (AMF). The path switching request signaling includes the received NCC counter value. The AMF determines the NCC and next-hop NH for key deduction based on the NCC counter value and sends a path switching request feedback signaling to the target node. The path switching request feedback signaling includes the NCC and NH for key deduction. The target node performs key deduction based on the NCC and NH to obtain a security key.

7. The method according to claim 1, characterized in that, The candidate node key information is obtained by the source node from the AMF.

8. The method according to claim 7, characterized in that, The AMF receives the candidate node list sent by the source node, generates one or more NCC values ​​for each candidate node, forms an NCC list, and obtains the candidate node key-related information.

9. The method according to claim 1, characterized in that, The method further includes: The system performs L3 measurements and reports the L3 measurement report to the source node, enabling the source node to determine LTM configuration based on the L3 measurement report. It then sends a handover request signaling to one or more candidate nodes, the handover request signaling including information related to the requested LTM candidate cells. The candidate nodes perform access control, and if they accept the LTM request, they send a handover request feedback signaling back to the source node. The source node then determines the candidate cell set and the corresponding candidate nodes.

10. The method according to any one of claims 1-9, characterized in that, The candidate node key-related information includes the following: Base station identifier or Next Generation Radio Access Network (NG-RAN) identifier; An NCC list, which contains one or more NCC values.

11. The method according to claim 10, characterized in that, The candidate node key information also includes an NCC counter.

12. A key update method, characterized in that, Applied to the source node, the method includes: Send RRC reconfiguration signaling to user equipment, the RRC reconfiguration signaling including candidate node key related information.

13. The method according to claim 12, characterized in that, The method further includes: The candidate node list is sent to the AMF, so that the AMF generates one or more NCC values ​​for each candidate node, forming an NCC list, and obtains the candidate node key-related information. Obtain the candidate node key information from the AMF.

14. The method according to claim 12, characterized in that, The method further includes: Receive L3 measurement reports sent by user equipment; Based on the L3 measurement report, a decision is made to configure LTM; Send a handover request signaling message to one or more candidate nodes. The handover request signaling message includes information related to the requested LTM candidate cell, so that the one or more candidate nodes can perform access control. If the LTM request is accepted, a handover request feedback signaling message is sent back to the source node. Based on the received handover request feedback signaling, the candidate cell set and corresponding candidate nodes are determined.

15. A key update method, characterized in that, Applied to the target node, the method includes: Receive an RRC reconfiguration complete message sent by the source node, wherein the RRC reconfiguration complete message includes an NCC counter value; The NCC counter value is used to indicate the NCC value used by the user equipment in this key deduction. The NCC value comes from candidate node key-related information, which is sent to the user equipment by the source node through RRC reconfiguration signaling.

16. The method according to claim 15, characterized in that, The method further includes: A path switching request signaling is sent to the AMF, the path switching request signaling including the received NCC counter value, so that the AMF determines the NCC and the next hop NH based on the NCC counter value, and feeds back a path switching request feedback signaling to the target node, the path switching request feedback signaling including the NCC and the NH derived by the key; A security key is obtained by key deduction based on the NCC and NH.

17. The method according to claim 15, characterized in that, The method further includes: Receive the handover request signaling sent by the source node; The LTM request is accepted, and a handover request feedback signaling is sent to the source node so that the source node can determine the candidate cell set and the corresponding candidate node based on the received handover request feedback signaling.

18. A key update method, characterized in that, The method, applied to the Access and Mobility Management Function (AMF), includes: Send candidate node key-related information to the source node so that the source node can send the candidate node key-related information to the user equipment via RRC reconfiguration signaling.

19. The method according to claim 18, characterized in that, The method further includes: The system receives a list of candidate nodes sent by the source node, generates one or more NCC values ​​for each candidate node to form an NCC list, and obtains the key-related information of the candidate nodes.

20. The method according to claim 18, characterized in that, The method further includes: The system receives a path switching request signaling sent by the target node, the path switching request signaling including an NCC counter value; the NCC counter value is sent by the user equipment to the target node through an RRC reconfiguration completion message, and the NCC counter value is the NCC counter value used by the user equipment in this key deduction. The NCC and next-hop NH for key derivation are determined based on the NCC counter value; The path switching request feedback signaling is sent back to the target node. The path switching request feedback signaling includes the NCC and NH for key deduction, so that the target node can perform key deduction based on the NCC and NH to obtain a security key.

21. A user equipment, characterized in that, include: The reconfiguration signaling receiving module is configured to receive RRC reconfiguration signaling sent by the source node, wherein the RRC reconfiguration signaling includes candidate node key-related information.

22. A network device, characterized in that, include: The reconfiguration signaling sending module is configured to send RRC reconfiguration signaling to the user equipment, wherein the RRC reconfiguration signaling includes candidate node key related information.

23. A network device, characterized in that, include: The message receiving module is configured to receive an RRC reconfiguration complete message sent by the source node, wherein the RRC reconfiguration complete message includes an NCC counter value; The NCC counter value is used to indicate the NCC value used by the user equipment in this key deduction. The NCC value comes from candidate node key-related information, which is sent to the user equipment by the source node through RRC reconfiguration signaling.

24. A mobility management function, characterized in that, include: The information sending module is configured to send candidate node key-related information to the source node, so that the source node can send the candidate node key-related information to the user equipment via RRC reconfiguration signaling.

25. A communication system, characterized in that, It includes the network device as described in claim 21, the network device as described in claim 22, the network device as described in claim 23, and the mobility management function as described in claim 24.

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