Defending Against IMSI-Catchers: Enforcing 5G Standalone (5G SA) Mutual Authentication & SUCI Encryption
How 5G Standalone mitigates rogue cellular surveillance: Subscription Concealed Identifier (SUCI) public key encryption and 2G disablement on modern handsets.
Legacy 2G and 3G networks transmit international mobile subscriber identities (IMSI) in cleartext over the air, exposing users to StingRay interception.
1. 5G SA Cryptographic Protections
SUCI Public Key Encryption
In 5G Standalone (5G SA), the handset encrypts the IMSI with the home network's public key (using ECIES / Curve25519) to generate a Subscription Concealed Identifier (SUCI). Even if a rogue base station captures the initial attach request, it cannot decrypt the subscriber identity.
- Mandatory Mutual Authentication: 5G AKA (Authentication and Key Agreement) requires both the user equipment and the core network to verify cryptographic tokens.
- Disable 2G Cellular Toggles: Android 12+ and iOS 17 allow users to disable 2G baseband radio completely, eliminating forced downgrade attacks.
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