Powerful quantum computers in the future may be able to break the security used for communication between vehicles and other devices (Vehicle-to-Everything, or V2X). New security methods called post-quantum cryptography can help protect these systems, but they often require more computing power and can slow down communication, posing a challenge for fast 6G vehicle networks. In this paper, we propose an adaptive post-quantum cryptography (PQC) framework that predicts short-term mobility and channel variations and dynamically selects suitable lattice-, code-, or hash-based PQC configurations using a predictive multi-objective evolutionary algorithm (APMOEA) to meet vehicular latency and security constraints.However, frequent cryptographic reconfiguration in dynamic vehicular environments introduces new attack surfaces during algorithm transitions. A secure monotonic-upgrade protocol prevents downgrade, replay, and desynchronization attacks during transitions. Theoretical results show decision stability under bounded prediction error, latency boundedness under mobility drift, and correctness under small forecast noise. These results demonstrate a practical path toward quantum-safe cryptography in future 6G vehicular networks. Through extensive experiments based on realistic mobility (LuST), weather (ERA5), and NR-V2X channel traces, we show that the proposed framework reduces end-to-end latency by up to 27\%, lowers communication overhead by up to 65\%, and effectively stabilizes cryptographic switching behavior using reinforcement learning. Moreover, under the evaluated adversarial scenarios, the monotonic-upgrade protocol successfully prevents downgrade, replay, and desynchronization attacks.

翻译：未来强大的量子计算机可能破解车辆与其他设备（车联万物，V2X）间通信所采用的安全机制。后量子密码学这一新型安全方法能够保护此类系统，但其通常需要更强的计算能力并可能降低通信速度，这对高速6G车联网构成挑战。本文提出一种自适应后量子密码框架，该框架通过预测短期移动性与信道变化，并利用预测性多目标进化算法动态选择基于格、编码或哈希的合适PQC配置，以满足车联网时延与安全约束。然而，动态车联环境中频繁的密码重配置会在算法切换期间引入新的攻击面。一种安全单调升级协议可防止切换过程中的降级、重放与去同步攻击。理论结果表明：在有限预测误差下决策具有稳定性，在移动漂移下时延有界，在微小预测噪声下系统保持正确性。这些结果为未来6G车联网实现抗量子密码提供了可行路径。基于真实移动性（LuST）、气象（ERA5）与NR-V2X信道轨迹的广泛实验表明：所提框架将端到端时延降低达27%，通信开销减少达65%，并通过强化学习有效稳定了密码切换行为。此外，在评估的对抗场景下，单调升级协议成功防御了降级、重放与去同步攻击。