SUCI (Subscription Concealed Identifier)

The Subscription Concealed Identifier is the encrypted form of the SUPI used in 5G to prevent passive over-the-air tracking. The UE generates a fresh SUCI for each transmission by encrypting the SUPI with the home network's public key (using ECIES), so a passive observer or rogue base station cannot derive the long-term subscriber identity. The home network's UDM/SIDF decrypts the SUCI back to the SUPI for authentication, closing one of the most exploited weaknesses of 2G/3G/4G.

Categories: Radio Access NetworkCore NetworkRoaming and Interconnect

SUCI in context

The radio access network is the layer where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations, downgrade attacks and jamming, and defenses hinge on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

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.

To place SUCI in the wider telecom-security picture, review AUSF, SUPI, SUPI Concealment, TMSI, AKA and BTS.

Related terms

Related topic hubs

  • 5G Security 5G SBA, SEPP, SUCI, 5G-AKA, N32 and service-based interface security.
  • Roaming Security IPX/GRX interconnect risk, home-routed vs local-breakout, SEPP.
  • Diameter Security 4G/LTE Diameter threats across IPX/roaming and DEA defenses.
  • Diameter Attacks S6a IDR/PUR/CLR abuse, subscriber tracking, LTE signaling attacks.

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.