3GPP 24.501 v20.0.0 — the document's own text
8.2.25.1 Message definition
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
The SECURITY MODE COMMAND message is sent by the AMF to the UE to establish NAS signalling security. See table 8.2.25.1.1.
Message type: SECURITY MODE COMMAND
Significance: dual
Direction: network to UE
Table 8.2.25.1.1: SECURITY MODE COMMAND message content
| IEI | Information Element | Type/Reference | Presence | Format | Length |
|---|---|---|---|---|---|
| Extended protocol discriminator | Extended protocol discriminator9.2 | M | V | 1 | |
| Security header type | Security header type9.3 | M | V | 1/2 | |
| Spare half octet | Spare half octet9.5 | M | V | 1/2 | |
| Security mode command message identity | Message type9.7 | M | V | 1 | |
| Selected NAS security algorithms | NAS security algorithms9.11.3.34 | M | V | 1 | |
| ngKSI | NAS key set identifier9.11.3.32 | M | V | 1/2 | |
| Spare half octet | Spare half octet9.5 | M | V | 1/2 | |
| Replayed UE security capabilities | UE security capability9.11.3.54 | M | LV | 3-9 | |
| E- | IMEISV request | IMEISV request9.11.3.28 | O | TV | 1 |
| 57 | Selected EPS NAS security algorithms | EPS NAS security algorithms9.11.3.25 | O | TV | 2 |
| 36 | Additional 5G security information | Additional 5G security information9.11.3.12 | O | TLV | 3 |
| 78 | EAP message | EAP message9.11.2.2 | O | TLV-E | 7-1503 |
| 38 | ABBA | ABBA9.11.3.10 | O | TLV | 4-n |
| 19 | Replayed S1 UE security capabilities | S1 UE security capability9.11.3.48A | O | TLV | 4-7 |
| 55 | AUN3 device security key | AUN3 device security key9.11.3.107 | O | TLV | 36-257 |
NOTE: It is possible for AMFs compliant with version 18.3.0 or 18.3.1 of this specification to send the AUN3 device security key IE with a fixed length of 66 octets.