LG Uplus to Encrypt IMSI in 5G Standalone, Randomize IDs for All Customers

LG Uplus announced that it will implement a stronger security framework across its network, starting April 13, and will offer free SIM swaps and resets to all customers as part of the rollout. The upgrade comes in response to concerns over IMSI exposure, which can potentially be leveraged for security threats such as SIM cloning when combined with other data.

In the 5G standalone SA environment, IMSI numbers will be encrypted by default, making their exposure effectively impossible. The IMSI is a 15-digit identifier stored on SIM cards that includes country code, operator ID, and subscriber number, and leaks can raise risks when linked with other data.

LG Uplus will also overhaul the IMSI structure itself. The company plans to adopt a new design that applies random numbers in the subscriber identification area, strengthening protection against predictable identifiers. The revised IMSI will automatically apply whenever a SIM is swapped or reset.

The free SIM swaps and resets will cover all LG Uplus customers, including users of smartwatches, kids’ phones, and MVNO customers who operate on LG Uplus networks. To reduce in-store wait times, the operator will operate an appointment system for service visits.

For customers who switch numbers or sign up after April 13, the new IMSI framework will automatically apply to the new SIM. The move follows an internal security review that identified enhancements were needed, with design and testing of the new IMSI system underway since June of last year.

Competitors in Korea’s mobile market have already taken similar steps; SK Telecom and KT are reported to assign unpredictable identifiers by using random numbers, a practice LG Uplus is adopting as part of broader industry efforts to harden user privacy and security.

Lee Jae-won, LG Uplus’s vice president, said the upgrade aims to let customers use mobile services more securely while minimizing any inconvenience during the transition. He noted that the changes are designed to be as frictionless as possible for users.

Why this matters beyond Korea: for U.S. readers, the development underscores how 5G networks are shifting toward stronger core-network security. Encrypting IMSI data in 5G SA environments reduces the risk of identity exposure and fraud for roaming users, which is increasingly important as cross-border mobile use grows. The move also signals how major operators are converging on non-predictable subscriber identifiers, potentially influencing global security standards, device security practices, and the reliability of international roaming and supply chains tied to mobile services.