Introducing Small Cell Networks (SCN) has significantly improved wireless link quality, spectrum efficiency and network capacity, which has been viewed as one of the key technologies in the fifth-generation (5G) mobile network. However, this technology increases the frequency of handover (HO) procedures caused by the dense deployment of cells in the network with reduced cell coverage, bringing new security and privacy issues. The current 5G-AKA and HO protocols are vulnerable to security weaknesses, such as the lack of forward secrecy and identity confusion attacks. The high HO frequency of HOs might magnify these security and privacy concerns in the 5G mobile network. This work addresses these issues by proposing a secure privacy-preserving universal HO scheme ($\UniHand$) for SCNs in 5G mobile communication. $\UniHand$ can achieve mutual authentication, strong anonymity, perfect forward secrecy, key-escrow-free and key compromise impersonation (KCI) resilience. To the best of our knowledge, this is the \textit{first} scheme to achieve secure, privacy-preserving universal HO with \textit{KCI} resilience for roaming users in 5G environment. We demonstrate that our proposed scheme is resilient against all the essential security threats by performing a comprehensive formal security analysis and conducting relevant experiments to show the cost-effectiveness of the proposed scheme.

翻译：摘要：引入小小区网络（SCN）显著提升了无线链路质量、频谱效率和网络容量，这已被视为第五代（5G）移动网络的关键技术之一。然而，该技术因小区密集部署导致覆盖范围缩小，增加了切换（HO）过程的频率，从而引发新的安全与隐私问题。当前的5G-AKA及HO协议存在安全漏洞，如缺乏前向安全性和身份混淆攻击。HO的高频次会放大5G移动网络中的这些安全与隐私风险。本研究提出一种面向5G移动通信中SCN的安全隐私保护通用HO方案（$\UniHand$），解决了上述问题。该方案可实现双向认证、强匿名性、完美前向保密性、免密钥托管及密钥泄露模拟（KCI）鲁棒性。据我们所知，这是5G环境下首个为漫游用户实现安全隐私保护通用HO且具备KCI鲁棒性的方案。通过全面的形式化安全分析与相关实验验证，我们证明所提方案能抵御所有关键安全威胁，并展示了其成本效益。