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 carries subscriber sessions, mobility and policy. 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.

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

To place GUTI in the wider telecom-security picture, review EIR, SAS, ADSL, AES, Conformance Testing and Confidentiality — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

More from the TelcoSec Glossary

Browse the full TelcoSec Glossary, the Ultimate Guide to Mobile Network Security, or the P1 Arsenal of telecom-security tools.