Zero-Knowledge Proof of Distinct Identity: a Standard-compatible Sybil-resistant Pseudonym Extension for C-ITS

TL;DR

The paper tackles Sybil attacks in C-ITS by proposing zk-PoDI, a locality-focused, non-intrusive pseudonym extension that proves distinct identity without revealing actual identities. It combines a Diophantine equation-based distinct identity criterion with zk-SNARKs to yield a zero-knowledge proof that two pseudonyms originate from different vehicles. The approach is non-interactive, scalable, and compatible with existing pseudonym frameworks, claiming low latency and minimal communication overhead. The authors present performance benchmarks using Groth16, discuss security considerations, and outline plans for city-scale validation in simulation environments.

Abstract

Pseudonyms are widely used in Cooperative Intelligent Transport Systems (C-ITS) to protect the location privacy of vehicles. However, the unlinkability nature of pseudonyms also enables Sybil attacks, where a malicious vehicle can pretend to be multiple vehicles at the same time. In this paper, we propose a novel protocol called zero-knowledge Proof of Distinct Identity (zk-PoDI,) which allows a vehicle to prove that it is not the owner of another pseudonym in the local area, without revealing its actual identity. Zk-PoDI is based on the Diophantine equation and zk-SNARK, and does not rely on any specific pseudonym design or infrastructure assistance. We show that zk-PoDI satisfies all the requirements for a practical Sybil-resistance pseudonym system, and it has low latency, adjustable difficulty, moderate computation overhead, and negligible communication cost. We also discuss the future work of implementing and evaluating zk-PoDI in a realistic city-scale simulation environment.

Figures (3)

• Figure 1: Arithmetic circuit overview
• Figure 2: Protocol overview
• Figure 3: Proof and verification time of zk-PoDI