5G • Security
NAS Security Mode Command
NAS Security Mode Control Procedure
Handshake procedure negotiating cryptographic ciphering and integrity algorithms between UE and AMF.
Technical Explanation
After 5G-AKA authentication, the AMF sends a SecurityModeCommand message containing selected encryption (NEA) and integrity (NIA) algorithms, the AMF's anti-replay replay counter, and a MAC-I. The UE verifies integrity, activates deciphering, and replies with an encrypted SecurityModeComplete message.
Key Functions
- Negotiates selected encryption (NEA) and integrity (NIA) algorithms
- Activates ciphering and integrity verification across the N1 interface
- Protected by mandatory Message Authentication Code (MAC-I)
Specifications
3GPP TS 24.501, TS 33.501
Interfaces
N1
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