GUTI (Globally Unique Temporary Identifier)

Also known as: 5G-GUTI, Globally Unique Temporary Identifier

GUTI is the temporary UE identifier assigned by the MME (in EPS) or AMF (in 5GS, where it is called 5G-GUTI) so that the permanent IMSI or SUPI does not need to be sent over the air after initial attach. Frequent GUTI reallocation is a key privacy control: weak or predictable GUTI reallocation is a known IMSI-catcher and tracking vulnerability documented by 3GPP and academic research.

Categories: Core NetworkIdentity and SubscriberProtocols and Standards

GUTI in context

The mobile core is where subscriber sessions, mobility and policy live. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF. Core exposure is the difference between a single-subscriber leak and a fleet-wide breach.

Subscriber identifiers (IMSI, SUPI, MSISDN, IMEI) are the anchor for authentication, charging, lawful interception and fraud analytics. Any protocol or interface that leaks a permanent identifier is treated as a serious privacy defect, which is why 5G introduced SUCI concealment on the air interface.

To place GUTI in the wider telecom-security picture, review 5G-GUTI, EIR, SAS, TMSI, GMSC and GSMA.

Related terms

Related topic hubs

  • 5G Security 5G SBA, SEPP, SUCI, 5G-AKA, N32 and service-based interface security.
  • NAS Security Non-Access Stratum security, integrity and ciphering algorithms.
  • Diameter Attacks S6a IDR/PUR/CLR abuse, subscriber tracking, LTE signaling attacks.
  • 5G NEF Security Network Exposure Function security in the 5G core.

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