AMMARIMohammedELAmineMEGRAHKaouther2025-11-112025MM/900https://dspace.univ-bba.dz/handle/123456789/1001In Vehicular Ad hoc Networks (VANETs), vehicles regularly broadcast critical information such as their position, speed, and direction to neighboring nodes. While essential for safety applications, this communication raises serious privacy concerns, particularly the risk of unau thorized vehicle tracking. To address this issue, various pseudonym change strategies have been proposed. In this work, we enhance an existing cooperative pseudonym change scheme, known as CPN (Cooperative Pseudonym Change based on the Number of Neighbors), by introducing new conditions and features, such as a silent period, that aim to strengthen the change pro cess and ensure it occurs only when necessary. The proposed solution is implemented within the PREXT framework and evaluated through simulation. The results demonstrate that our approach achieves a better balance between pseudonym efficiency and privacy protection, re ducing the risk of vehicle traceability while avoiding unnecessary pseudonym consumption.enVANETprivacysecuritypseudonym changesilent periodPREXTThesis