NAS security vs AS security
LTE and 5G both split radio-side security into two layers. NAS (Non-Access Stratum) protects signaling between the UE and the core (MME / AMF). AS (Access Stratum) protects the radio-side link between the UE and the base station.
| Attribute | NAS security | AS security |
|---|---|---|
| Endpoint | UE ↔ MME (LTE) / AMF (5G) | UE ↔ eNB / gNB |
| Purpose | Mobility, authentication, session mgmt | RRC signaling and user-plane radio |
| Algorithms | EEA/EIA (LTE), NEA/NIA (5G) | Same algorithm families |
| Downgrade risk | "NULL integrity" fallback historically | Rogue-base-station downgrade |
Verdict
Attackers have historically pushed both layers to NULL algorithms. Compliance frameworks now forbid NULL integrity on NAS, but AS-side downgrades via rogue cells remain a live problem — this is where 5G SUCI matters most.