A joint trajectory obfuscation and pseudonym swapping mechanism avoiding extra privacy cost

Author Identifier (ORCID)

Wei Ni: https://orcid.org/0000-0002-4933-594X

Abstract

Vehicular networks generate rich spatio-temporal data that could expose drivers to trajectory inference, identity linkage, and long-term tracking. Differential Privacy (DP) and pseudonym swapping are widely used mechanisms for protecting location privacy and identity–location unlinkability, respectively. Existing attempts to combine the two treat them as independent procedures and fail to recognize that both mechanisms rely on noise injection, causing their noises to accumulate and leading to unnecessary privacy-budget consumption, as well as degraded communication reliability and downstream location-based service quality. This paper presents a new perspective for jointly integrating the two mechanisms by formulating the pseudonym-swapping candidate identity pool as a DP-equivalent process. We firstly introduce Trajectory-Indistinguishability (T-I), a unified metric that evaluates indistinguishability across both identity and trajectory dimensions. Building on T-I, we present JTOPS, a Joint Trajectory Obfuscation and Pseudonym-Swapping mechanism that performs both operations under a single DP-based framework. JTOPS obfuscates each vehicle’s spatio-temporal trajectory locally and then computes pseudonym-swapping probabilities using these obfuscated trajectories, ensuring that both operations share a unified DP formulation rather than consuming privacy budget separately. JTOPS eliminates unnecessary privacy loss, preserves trajectory fidelity, and sustains privacy even when adversaries compromise the coordinator. We mathematically prove that JTOPS satisfies T-I and remains robust under long-term observation. Experiments on real road-network trajectories show that JTOPS reduces attack success rates by over 80% while maintaining more than 95% trajectory utility, outperforming representative state-of-the-art methods.

Keywords

Location privacy, pseudonym, road network-indistinguishability, trajectory obfuscation

Document Type

Journal Article

Date of Publication

1-1-2026

Publication Title

IEEE Transactions on Intelligent Transportation Systems

Publisher

IEEE

School

School of Engineering

Comments

Ma, B., Wang, X., Yu, G., Jiang, Y., Zhu, S., Liu, B., He, Y., Ni, W., & Liu, R. P. (2026). A joint trajectory obfuscation and pseudonym swapping mechanism avoiding extra privacy cost. IEEE Transactions on Intelligent Transportation Systems. Advance online publication. https://doi.org/10.1109/TITS.2026.3669530

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Link to publisher version (DOI)

10.1109/TITS.2026.3669530