5G identifiers
In telecommunication systems, the network operator allocates a SIM card to every device. This SIM card is associated not just with the mobile number but also with a SUPI in the 5GS. It was known as International Mobile Subscriber Identity (IMSI) in the 4G world.
Figure 2.21 – 5G identifiers
The authentication of the UE and the network is based on symmetric keys and is dependent on the identification of the user. However, if the identification is sent in cleartext over the air from the UE to the network, it is susceptible to being imitated by malicious entities, who can pose as legitimate users. To avoid this, mobile networks use several temporary identifiers called Globally Unique Temporary Identifiers (GUTIs).
These identifiers are frequently changed and used for identifying a UE over the air. However, in some situations, like the first user registration, the SUPI is used, and then from thereon, a GUTI is used:
