# US 2021/0243687 A1 · Processing Method for Security Algorithm and Terminal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0243687 A1 - Document ID: US20210243687A1 - Status: Published application - Kind: A1 - Application number: 17/235,668 - Filed: 2021-04-20 - Published: 2021-08-05 - Earliest claimed: 2018-10-23 - Assignees: Guangdong Oppo Mobile Telecommunications Corp., Ltd. - Applicants: Guangdong Oppo Mobile Telecommunications Corp., Ltd. - Inventors: Shukun Wang; Ning Yang - Web page: https://patentgrep.com/patent/US20210243687A1 ## CPC - H04W 48/20: Selecting an access point - H04W 12/03: Protecting confidentiality, e.g. by encryption - H04W 12/037: of the control plane, e.g. signalling traffic - H04W 12/04: Key management, e.g. using generic bootstrapping architecture [GBA] - H04W 12/08: Access security - H04W 12/106: Packet or message integrity - H04W 36/0038: {of security context information} - H04W 48/16: Discovering, processing access restriction or access information - H04W 76/19: Connection re-establishment - H04W 76/27: Transitions between radio resource control [RRC] states - H04W 36/0079: {in case of hand-off failure or rejection} - H04W 36/305: {Handover due to radio link failure (control signalling for hand-off failure H04W36/0079)} - H04W 56/00: Synchronisation arrangements - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Implementations of the present disclosure provide a processing method and apparatus for a security algorithm and a terminal. The method includes the following. A terminal performs cell search and selects a cell supporting a security algorithm as a target cell from found cells, where the security algorithm is used by the terminal before RRC connection re-establishment or RRC connection recovery. The terminal performs an RRC connection re-establishment procedure or an RRC connection recovery procedure between the terminal and the target cell. ## Claims ### Claim 1 A method for processing a security algorithm, comprising: performing, by a terminal, cell search, and selecting, by the terminal, a cell supporting a security algorithm as a target cell from found cells, wherein the security algorithm is used by the terminal before radio resource control (RRC) connection re-establishment or RRC connection recovery; and performing, by the terminal, an RRC connection re-establishment procedure or an RRC connection recovery procedure between the terminal and the target cell. ### Claim 2 (depends on 1) The method of claim 1, further comprising: for each of at least one cell, obtaining, by the terminal, a security algorithm list supported by the cell from a system broadcast message of the cell, wherein the security algorithm list contains at least one security algorithm support by the cell. ### Claim 3 (depends on 1) The method of claim 1, wherein performing, by the terminal, the RRC connection re-establishment procedure between the terminal and the target cell comprises: transmitting, by the terminal, an RRC connection re-establishment request message to the target cell; receiving, by the terminal, an RRC connection re-establishment message from the target cell, wherein the RRC connection re-establishment message has been subjected to integrity protection performed with the security algorithm and a secret key updated by the target cell; and transmitting, by the terminal, an RRC connection re-establishment completion message to the target cell. ### Claim 4 (depends on 3) The method of claim 3, wherein the RRC connection re-establishment message carries next hop chaining count (NCC) information, wherein the NCC information is used by the terminal to update a secret key; the method further comprises: performing, by the terminal, integrity protection and encryption on the RRC connection re-establishment completion message with the security algorithm and the secret key updated by the terminal. ### Claim 5 (depends on 1) The method of claim 1, wherein performing, by the terminal, the RRC connection recovery procedure between the terminal and the target cell comprises: transmitting, by the terminal, an RRC connection recovery request message to the target cell; receiving, by the terminal, an RRC connection recovery message from the target cell, wherein the RRC connection recovery message has been subjected to integrity protection and encryption performed with the security algorithm and a secret key updated by the target cell; and transmitting, by the terminal, an RRC connection recovery completion message to the target cell. ### Claim 6 (depends on 5) The method of claim 5, wherein the RRC connection recovery message carries NCC information, wherein the NCC information is used by the terminal to update a secret key; the method further comprises: performing, by the terminal, integrity protection and encryption on the RRC connection recovery completion message with the security algorithm and the secret key updated by the terminal. ### Claim 7 A method for processing a security algorithm, comprising: performing, by a terminal, cell search, and selecting, by the terminal, a target cell from found cells; transmitting, by the terminal, a radio resource control (RRC) connection re-establishment request message to the target cell; receiving, by the terminal, an RRC connection re-establishment message from the target cell, and determining, by the terminal, whether the RRC connection re-establishment message carries configuration information of a security algorithm supported by the target cell; and transmitting, by the terminal, an RRC connection re-establishment completion message to the target cell via the security algorithm supported by the target cell, in response to the RRC connection re-establishment message carrying the configuration information of the security algorithm supported by the target cell. ### Claim 8 (depends on 7) The method of claim 7, wherein the RRC connection re-establishment message carrying the configuration information of the security algorithm supported by the target cell is indicative of that a security algorithm used by the terminal before RRC connection re-establishment is not supported by the target cell. ### Claim 9 (depends on 7) The method of claim 7, wherein the RRC connection re-establishment message not carrying the configuration information of the security algorithm supported by the target cell or carrying the configuration information of the security algorithm supported by the target cell is indicative of that a security algorithm used by the terminal before RRC connection re-establishment is supported by the target cell. ### Claim 10 (depends on 7) The method of claim 7, wherein the RRC connection re-establishment message has been subjected to integrity protection performed with the security algorithm supported by the target cell and a secret key updated by the target cell, on condition that the RRC connection re-establishment message carries the configuration information of the security algorithm supported by the target cell. ### Claim 11 (depends on 7) The method of claim 7, wherein the RRC connection re-establishment message carries next hop chaining count (NCC) information, wherein the NCC information is used by the terminal to update a secret key; the method further comprises: performing, by the terminal, integrity protection and encryption on the RRC connection re-establishment completion message with the security algorithm supported by the target cell and the secret key updated by the terminal, in response to the RRC connection re-establishment message carrying the configuration information of the security algorithm supported by the target cell. ### Claim 12 (depends on 7) The method of claim 7, further comprising: transmitting, by the terminal, the RRC connection re-establishment completion message to the target cell via a security algorithm used by the terminal before RRC connection re-establishment, in response to the RRC connection re-establishment message not carrying the configuration information of the security algorithm supported by the target cell. ### Claim 13 (depends on 12) The method of claim 12, wherein the RRC connection re-establishment message carries NCC information, wherein the NCC information is used by the terminal to update a secret key; and the method further comprises: performing, by the terminal, integrity protection and encryption on the RRC connection re-establishment completion message with the security algorithm used by the terminal before the RRC connection re-establishment and the secret key updated by the terminal, in response to the RRC connection re-establishment message not carrying the configuration information of the security algorithm supported by the target cell. ### Claim 14 A terminal comprising: at least one processor; and a memory storing computer programs which, when executed by the at least one processor, cause the at least one processor to: perform cell search and select a cell supporting a security algorithm as a target cell from found cells, wherein the security algorithm is used by the terminal before radio resource control (RRC) connection re-establishment or RRC connection recovery; and perform an RRC connection re-establishment procedure or an RRC connection recovery procedure between the terminal and the target cell. ### Claim 15 (depends on 14) The terminal of claim 14, wherein the computer programs further cause the at least one processor to: obtain, for each of at least one cell, a security algorithm list supported by the cell from a system broadcast message of the cell, wherein the security algorithm list contains at least one security algorithm support by the cell. ### Claim 16 (depends on 14) The terminal of claim 14, wherein the computer programs causing the at least one processor to perform the RRC connection re-establishment procedure between the terminal and the target cell cause the at least one processor to: transmit an RRC connection re-establishment request message to the target cell; receive an RRC connection re-establishment message from the target cell, wherein the RRC connection re-establishment message has been subjected to integrity protection performed with the security algorithm and a secret key updated by the target cell; and transmit an RRC connection re-establishment completion message to the target cell. ### Claim 17 (depends on 16) The terminal of claim 16, wherein the RRC connection re-establishment message carries next hop chaining count (NCC) information, wherein the NCC information is used by the terminal to update a secret key; the computer programs further cause the at least one processor to: perform integrity protection and encryption on the RRC connection re-establishment completion message with the security algorithm and the secret key updated by the terminal. ### Claim 18 (depends on 14) The terminal of claim 14, wherein the computer programs causing the at least one processor to perform the RRC connection recovery procedure between the terminal and the target cell cause the at least one processor to: transmit an RRC connection recovery request message to the target cell; receive an RRC connection recovery message from the target cell, wherein the RRC connection recovery message has been subjected to integrity protection and encryption performed with the security algorithm and a secret key updated by the target cell; and transmit an RRC connection recovery completion message to the target cell. ### Claim 19 (depends on 18) The terminal of claim 18, wherein the RRC connection recovery message carries NCC information, wherein the NCC information is used by the terminal to update a secret key; the computer programs further cause the at least one processor to: perform integrity protection and encryption on the RRC connection recovery completion message with the security algorithm and the secret key updated by the terminal. ### Claim 20 (depends on 14) The terminal of claim 14, wherein the target cell has the highest signal quality among the found cells.