Service discovery is a fundamental process in wireless networks, enabling devices to find and communicate with services dynamically, and is critical for the seamless operation of modern systems like 5G and IoT. This paper introduces PriSrv+, an advanced privacy and usability-enhanced service discovery protocol for modern wireless networks and resource-constrained environments. PriSrv+ builds upon PriSrv (NDSS'24), by addressing critical limitations in expressiveness, privacy, scalability, and efficiency, while maintaining compatibility with widely-used wireless protocols such as mDNS, BLE, and Wi-Fi. A key innovation in PriSrv+ is the development of Fast and Expressive Matchmaking Encryption (FEME), the first matchmaking encryption scheme capable of supporting expressive access control policies with an unbounded attribute universe, allowing any arbitrary string to be used as an attribute. FEME significantly enhances the flexibility of service discovery while ensuring robust message and attribute privacy. Compared to PriSrv, PriSrv+ optimizes cryptographic operations, achieving 7.62* faster for encryption and 6.23* faster for decryption, and dramatically reduces ciphertext sizes by 87.33%. In addition, PriSrv+ reduces communication costs by 87.33% for service broadcast and 86.64% for anonymous mutual authentication compared with PriSrv. Formal security proofs confirm the security of FEME and PriSrv+. Extensive evaluations on multiple platforms demonstrate that PriSrv+ achieves superior performance, scalability, and efficiency compared to existing state-of-the-art protocols.

翻译：服务发现是无线网络中的基础流程，使设备能够动态发现并通信服务，对5G和物联网等现代系统的无缝运行至关重要。本文提出PriSrv+，一种面向现代无线网络及资源受限环境的增强型隐私与可用性服务发现协议。PriSrv+在PriSrv（NDSS'24）基础上，通过解决表达性、隐私性、可扩展性和效率方面的关键限制，同时保持对mDNS、BLE和Wi-Fi等广泛使用的无线协议的兼容性。PriSrv+的核心创新在于开发了快速与表达性匹配加密（FEME），这是首个能够支持无界属性宇宙中表达性访问控制策略的匹配加密方案，允许任意字符串作为属性使用。FEME在确保强健消息与属性隐私的同时，显著提升了服务发现的灵活性。与PriSrv相比，PriSrv+优化了密码学操作：加密速度提升7.62倍，解密速度提升6.23倍，密文体积减小87.33%。此外，PriSrv+的服务广播通信成本较PriSrv降低87.33%，匿名相互认证通信成本降低86.64%。形式化安全证明验证了FEME及PriSrv+的安全性。多平台上的广泛评估表明，相较于现有最优协议，PriSrv+实现了更卓越的性能、可扩展性与效率。