SUPI
Subscription Permanent Identifier: the globally unique permanent identifier for a 5G subscriber (typically IMSI format), never transmitted in cleartext over the air interface.
The SUPI is the subscriber's true, permanent identity in 5G — the thing the home network's UDM uses to look up who you are and what you're subscribed to. In most deployments it's an IMSI under the hood; it can also be a network-specific identifier for non-3GPP access. The defining rule is that it never goes over the radio interface in the clear. Where 4G would sometimes send the IMSI in plaintext (the weakness that IMSI catchers exploited), 5G forbids it.
So the SUPI lives in the USIM and in the core, and on the air the UE sends the SUCI instead — an encrypted wrapper around the SUPI. The home network unwraps the SUCI back to the SUPI to authenticate. Once the subscriber is known, the AMF assigns a temporary identity (the 5G-GUTI) for subsequent signalling so even the concealed identifier isn't sent repeatedly. The SUPI / SUCI analyzer takes a concealed identity apart field by field, and SUCI and SUPI privacy is the same question in a capture.
Frequently asked questions
- SUPI vs SUCI — what is the actual difference?
- The SUPI is the permanent subscriber identity (usually the IMSI). The SUCI is its privacy-protected form: the UE encrypts the identifying part of the SUPI (the MSIN) with the home operator's public key before transmitting it, leaving the MCC/MNC routing prefix readable. So they describe the same identity at two stages — SUPI is the cleartext value held on the USIM and in the core, SUCI is the concealed value sent over the air during registration. The home network decrypts the SUCI to recover the SUPI.
Related terms
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