NAS Key Synchronization in Wireless Communications
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Solution Overview
Problem
In wireless communication systems, such as LTE and 5G networks, security key synchronization between mobile communication devices and network entities can become out of sync, leading to communication failures due to abnormal scenarios where acknowledge messages are not received in a timely manner, causing key asynchronization issues.
Innovation Solution
A communications apparatus and method that performs a Non Access Stratum (NAS) security mode command procedure to derive NAS keys, transmits a NAS security mode complete message, and receives an RRCReconfiguration message to derive Access Stratum (AS) keys, even if the acknowledge message for the NAS security mode complete message is not received, allowing continued communication using the NAS keys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the communications apparatus waits for an acknowledge message before deriving AS keys, then key synchronization reliability is improved, but communication continuity deteriorates in abnormal scenarios where the acknowledge message is not received
Solution Approach 1:
The communications apparatus performs the NAS security mode command procedure to derive NAS keys in advance, before receiving the RRCReconfiguration message. This preliminary action ensures that when the acknowledge message is not received, the device already has valid NAS keys ready for use, preventing communication interruption while maintaining key synchronization reliability
Solution Approach 2:
The patent converts the harmful effect of not receiving the acknowledge message into a benefit by designing the device to derive NAS keys independently of the acknowledge message reception. The abnormal scenario (harm) becomes an opportunity to demonstrate robust key derivation that doesn't depend on message acknowledgment, thereby improving communication continuity without sacrificing reliability
2Measurement precision
If the communications apparatus aborts newly derived NAS keys when acknowledge message is not received, then key synchronization accuracy is improved, but communication performance deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the device monitors whether the acknowledge message is received, but uses this feedback differently - not to abort key derivation, but to determine subsequent communication procedures. The NAS keys derived from the security mode command are used for subsequent NAS procedures regardless of acknowledge message reception, maintaining both synchronization accuracy and communication performance
Solution Approach 2:
The patent changes the operational parameter from 'abort key derivation on acknowledge failure' to 'continue using derived NAS keys for subsequent procedures'. This parameter change allows the system to maintain key synchronization accuracy while improving communication performance by preventing unnecessary key abortions in abnormal scenarios
Data Source
AI summary
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).