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Privacy-Preserving Identifier Checking in 5G

Marcel D. S. K. Gräfenstein, Stefan Köpsell, Maryam Zarezadeh

TL;DR

The paper tackles privacy risks from exposing PEIs during 5G identifier checks by introducing a BFV-homomorphic, PEPSI-based Private Set Membership protocol that verifies blacklist/greylist membership without revealing the PEI. It implements an auditable Law-Enforcement hook for lawful deanonymization and preserves EIR-like functionality within 3GPP workflows. Through offline preprocessing and a 1.5-round online protocol, it achieves practical latency (<5 s) and around 16 MB of per-session communication under post-quantum security, validated on large-scale IMEI datasets. The results demonstrate the feasibility of scalable, privacy-preserving PEI verification in 5G and beyond, while outlining trade-offs in bandwidth, noise-budget management, and potential leakage under repeated queries.

Abstract

Device identifiers like the International Mobile Equipment Identity (IMEI) are crucial for ensuring device integrity and meeting regulations in 4G and 5G networks. However, sharing these identifiers with Mobile Network Operators (MNOs) brings significant privacy risks by enabling long-term tracking and linking of user activities across sessions. In this work, we propose a privacy-preserving identifier checking method in 5G. This paper introduces a protocol for verifying device identifiers without exposing them to the network while maintaining the same functions as the 3GPP-defined Equipment Identity Register (EIR) process. The proposed solution modifies the PEPSI protocol for a Private Set Membership (PSM) setting using the BFV homomorphic encryption scheme. This lets User Equipment (UE) prove that its identifier is not on an operator's blacklist or greylist while ensuring that the MNO only learns the outcome of the verification. The protocol allows controlled deanonymization through an authorized Law Enforcement (LE) hook, striking a balance between privacy and accountability. Implementation results show that the system can perform online verification within five seconds and requires about 15 to 16 MB of communication per session. This confirms its practical use under post-quantum security standards. The findings highlight the promise of homomorphic encryption for managing identifiers while preserving privacy in 5G, laying the groundwork for scalable and compliant verification systems in future 6G networks.

Privacy-Preserving Identifier Checking in 5G

TL;DR

The paper tackles privacy risks from exposing PEIs during 5G identifier checks by introducing a BFV-homomorphic, PEPSI-based Private Set Membership protocol that verifies blacklist/greylist membership without revealing the PEI. It implements an auditable Law-Enforcement hook for lawful deanonymization and preserves EIR-like functionality within 3GPP workflows. Through offline preprocessing and a 1.5-round online protocol, it achieves practical latency (<5 s) and around 16 MB of per-session communication under post-quantum security, validated on large-scale IMEI datasets. The results demonstrate the feasibility of scalable, privacy-preserving PEI verification in 5G and beyond, while outlining trade-offs in bandwidth, noise-budget management, and potential leakage under repeated queries.

Abstract

Device identifiers like the International Mobile Equipment Identity (IMEI) are crucial for ensuring device integrity and meeting regulations in 4G and 5G networks. However, sharing these identifiers with Mobile Network Operators (MNOs) brings significant privacy risks by enabling long-term tracking and linking of user activities across sessions. In this work, we propose a privacy-preserving identifier checking method in 5G. This paper introduces a protocol for verifying device identifiers without exposing them to the network while maintaining the same functions as the 3GPP-defined Equipment Identity Register (EIR) process. The proposed solution modifies the PEPSI protocol for a Private Set Membership (PSM) setting using the BFV homomorphic encryption scheme. This lets User Equipment (UE) prove that its identifier is not on an operator's blacklist or greylist while ensuring that the MNO only learns the outcome of the verification. The protocol allows controlled deanonymization through an authorized Law Enforcement (LE) hook, striking a balance between privacy and accountability. Implementation results show that the system can perform online verification within five seconds and requires about 15 to 16 MB of communication per session. This confirms its practical use under post-quantum security standards. The findings highlight the promise of homomorphic encryption for managing identifiers while preserving privacy in 5G, laying the groundwork for scalable and compliant verification systems in future 6G networks.

Paper Structure

This paper contains 7 sections, 1 equation, 2 figures, 2 tables, 2 algorithms.

Table of Contents

  1. Introduction
  2. Related Work
  3. Preliminaries
  4. Proposed Method
  5. Protocol Architecture and Phases
  6. Complexity (Unbalanced Setting)
  7. Evaluation

Figures (2)

  • Figure 1: Identifier-verification protocol overview.
  • Figure 2: Cumulative success probability for a uniformly guessed value in a space of size $t_{\mathrm{eff}} = 516{,}095$ over $x$ attempts (logarithmic scale). The expected number of attempts until the first success is $1/p = t_{\mathrm{eff}}$.