5G • Security
AS Security Mode Command
Access Stratum Security Mode Control
RRC procedure activating over-the-air encryption and integrity protection in the PDCP layer.
Technical Explanation
The gNodeB initiates AS Security by sending an RRC SecurityModeCommand specifying chosen ciphering and integrity algorithms, protected by an integrity MAC-I calculated using K_RRCint. The UE verifies the MAC, derives AS keys from K_gNB, and replies with SecurityModeComplete. All subsequent RRC and user plane data is encrypted.
Key Functions
- Activates over-the-air encryption and integrity protection in PDCP
- Negotiates radio layer ciphering and integrity algorithms
- Secures all subsequent data radio bearers (DRBs) and signaling bearers
Specifications
3GPP TS 38.331, TS 33.501
Interfaces
Uu
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