# US 11,310,661 B2 · Security key synchronization method and associated communications apparatus

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- Number: US 11,310,661 B2
- Document ID: US11310661B2
- Status: Granted
- Kind: B2
- Application number: 16/790,762
- Filed: 2020-02-14
- Published: 2021-08-19
- Granted: 2022-04-19
- Earliest claimed: 2020-02-14
- Assignees: Mediatek Inc.
- Applicants: Mediatek Inc.
- Inventors: Yu-Lun Chang; Shih-Chieh Liao
- Web page: https://patentgrep.com/patent/US11310661B2

## CPC

- H04W 12/04: Key management, e.g. using generic bootstrapping architecture [GBA]
- H04W 12/041: Key generation or derivation
- H04L 63/06: {for supporting key management in a packet data network (cryptographic mechanisms or cryptographic arrangements for key management H04L9/08)}
- H04L 63/205: {involving negotiation or determination of the one or more network security mechanisms to be used, e.g. by negotiation between the client and the server or between peers or by selection according to the capabilities of the entities involved (negotiation of communication capabilities H04L69/24)}
- H04W 12/037: of the control plane, e.g. signalling traffic
- H04W 12/0433: Key management protocols
- H04W 12/06: Authentication
- H04W 12/08: Access security
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A communications apparatus includes a transceiver and a processor. The processor is configured to perform operations comprising: performing a Non Access Stratum (NAS) security mode command procedure to derive a set of NAS key(s); transmitting a NAS security mode complete message to a network device for informing that the NAS security mode command procedure is complete; receiving an RRCReconfiguration message indicating derivation of a set of Access Stratum (AS) keys from the network device when an acknowledge message associated with the NAS security mode complete message has not been received; and performing a NAS procedure to communicate with the network device by using the set of NAS key(s).

## Claims

### Claim 1

A communications apparatus, comprising:
a transceiver, transmitting or receiving wireless signals to communicate with a network device; and
a processor, coupled to the transceiver and configured to perform operations comprising:
performing a Non Access Stratum (NAS) security mode command procedure to derive a new set of NAS key(s) in response to a NAS security mode command message received from the network device;
transmitting a NAS security mode complete message to the network device for informing the network device that the NAS security mode command procedure is complete; and
performing a NAS procedure to communicate with the network device by using the new set of NAS key(s) instead of any sets of NAS key(s) derived before deriving the new set of NAS key(s) in response to reception of an RRCReconfiguration message indicating derivation of a set of Access Stratum (AS) keys from the network device when an acknowledge message associated with the NAS security mode complete message has not been received from the network device after transmitting the NAS security mode complete message.

### Claim 2 (depends on 1)

The communications apparatus of claim 1, wherein the processor is further configured to perform operation comprising:
determining whether the NAS procedure has failed;
aborting the new set of NAS key(s) based on a determination result.

### Claim 3 (depends on 2)

The communications apparatus of claim 2, wherein in the step of aborting the new set of NAS key(s) based on the determination result, the processor further performs operations comprising:
aborting the new set of NAS key(s) responsive to the determination result indicating that NAS procedure has failed.

### Claim 4 (depends on 3)

The communications apparatus of claim 3, wherein the processor is further configured to perform operations comprising:
performing another NAS procedure to communicate with the network device by using a previous set of NAS key(s) after aborting the new set of NAS key(s).

### Claim 5 (depends on 2)

The communications apparatus of claim 2, wherein in the step of aborting the new set of NAS key(s) based on the determination result, the processor further performs operations comprising:
aborting the new set of NAS key(s) only if the determination result indicating that NAS procedure has failed.

### Claim 6

A security key synchronization method for synchronizing security key(s) derived by a communications apparatus with security key(s) derived by a network device, wherein the security key synchronization method is performed by a processor of the communications apparatus and comprises:
performing a Non Access Stratum (NAS) security mode command procedure to derive a new set of NAS key(s) in response to a NAS security mode command message received from the network device;
transmitting a NAS security mode complete message to the network device for informing the network device that the NAS security mode command procedure is complete; and
performing a NAS procedure to communicate with the network device by using the new set of NAS key(s) instead of any sets of NAS key(s) derived before deriving the new set of NAS key(s) in response to reception of an RRCReconfiguration message indicating derivation of a set of Access Stratum (AS) keys from the network device when an acknowledge message associated with the NAS security mode complete message has not been received from the network device after transmitting the NAS security mode complete message to the network device.

### Claim 7 (depends on 6)

The security key synchronization method of claim 6, further comprising:
determining whether the NAS procedure has failed;
aborting the new set of NAS key(s) based on a determination result.

### Claim 8 (depends on 7)

The security key synchronization method of claim 7, wherein the step of aborting the new set of NAS key(s) based on the determination result further comprises:
aborting the new set of NAS key(s) responsive to the determination result indicating that NAS procedure has failed.

### Claim 9 (depends on 8)

The security key synchronization method of claim 8, further comprising:
performing another NAS procedure to communicate with the network device by using a previous set of NAS key(s) after aborting the new set of NAS key(s).

### Claim 10 (depends on 6)

The security key synchronization method of claim 6, wherein the step of aborting the new set of NAS key(s) based on the determination result further comprises:
aborting the new set of NAS key(s) only if the determination result indicating that NAS procedure has failed.