9.3 Security header type
24.5013GPPNon-Access-Stratum (NAS) protocol for 5G System (5GS)Release 18Stage 3TS
Bits 1 to 4 of the second octet of every 5GMM message contain the Security header type IE. This IE includes control information related to the security protection of a 5GMM message. The total size of the Security header type IE is 4 bits.
The Security header type IE can take the values shown in table 9.3.1.
Table 9.3.1: Security header type
|
Security header type (octet 1) |
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|
Bits |
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|
4 |
3 |
2 |
1 |
|
|
0 |
0 |
0 |
0 |
Plain 5GS NAS message, not security protected |
|
Security protected 5GS NAS message: |
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|
0 |
0 |
0 |
1 |
Integrity protected |
|
0 |
0 |
1 |
0 |
Integrity protected and ciphered |
|
0 |
0 |
1 |
1 |
Integrity protected with new 5G NAS security context (NOTE 1) |
|
0 |
1 |
0 |
0 |
Integrity protected and ciphered with new 5G NAS security context (NOTE 2) |
|
All other values are reserved. |
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NOTE 1: This codepoint may be used only for a SECURITY MODE COMMAND message. NOTE 2: This codepoint may be used only for a SECURITY MODE COMPLETE message. |
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A 5GMM message received with the security header type encoded as 0000 shall be treated as not security protected, plain 5GS NAS message. A protocol entity sending a not security protected 5GMM message shall send the message as plain 5GS NAS message and encode the security header type as 0000.