Identity Query is the 5GMM procedure where the network asks the UE to provide a specific identity. In 5G, the network commonly requests SUCI when it cannot identify the UE from the temporary identity supplied earlier. The UE returns Identity Response containing the requested mobile identity.
Signaling Sequence
# |
Direction |
5GMM Message |
Comment |
1 | AMF -> UE | Identity request | Network indicates the identity type it wants from the UE. |
2 | UE -> AMF | Identity response | UE returns the requested mobile identity. |
Message Structure
Identity Request contains the requested identity type. Identity Response contains the mobile identity itself, such as SUCI, 5G-GUTI, IMEI, or IMEISV depending on what the network requested.
Example : Identity Request
The following example is based on an Amarisoft MME log where the AMF requests SUCI. The whole decoded NAS message is shown below.
04:09:33.961 [NAS] DL 0064 5GMM: Identity request
Protocol discriminator = 0x7e (5GS Mobility Management)
Security header = 0x0 (Plain 5GS NAS message, not security protected)
Message type = 0x5b (Identity request)
Identity type = 0x1 (SUCI)
Example : Identity Response
The following example is based on the matching Identity Response in the same Amarisoft MME log. The whole decoded NAS message is shown below.
04:09:33.981 [NAS] UL 0064 5GMM: Identity response
Protocol discriminator = 0x7e (5GS Mobility Management)
Security header = 0x1 (Integrity protected)
Auth code = 0xef602896
Sequence number = 0x09
Protocol discriminator = 0x7e (5GS Mobility Management)
Security header = 0x0 (Plain 5GS NAS message, not security protected)
Message type = 0x5c (Identity response)
Mobile identity:
SUCI
SUPI format = 0 (IMSI)
MCC = 001
MNC = 01
Routing indicator = 0
Protection sheme id = 0 (Null scheme)
Home network public key identifier = 0
MSIN = 0123456789