Collaborative Research: Preserving User Privacy in Server-driven Dynamic Spectrum Access System

动态频谱接入技术（Dynamic spectrum access， DSA）是指无线设备在不干扰现有用户的情况下，使用分配给授权现有用户的频谱。它已被广泛认为是缓解无线通信频谱短缺问题的关键解决方案。作为DSA的一种关键形式，监管机构提议在频谱接入系统（SAS）数据库的保护下，释放更多的联邦频谱，供商业无线用户共享，以管理u和su之间的频谱共享。然而，这种共享的成功取决于如何管理隐私问题。在目前的SAS方案中，联邦u和商用u的运行数据都需要与SAS数据库共享，由SAS数据库决定是否允许共享。然而，联邦单位的操作数据往往属于机密信息，SU的操作数据也可能属于商业机密。由于SAS不一定由受信任的第三方操作，并且可能被攻击者破坏，因此这些当前的方案威胁到u和u的隐私。为了解决这一隐私问题，本项目开发了一种保护隐私的SAS (P2-SAS)，确保SAS系统在不了解u和u的运行数据的情况下，仍能准确判断u和u之间是否允许共享频谱。该项目是第一个能够在SAS中成功实现保护隐私的频谱分配的项目。它解决了监管机构对DSA隐私问题的担忧，从而极大地帮助了整个国家宽带网络的发展。该项目为如何将隐私保护机制集成到DSA以外的许多其他通信系统中提供了蓝图。该方案利用安全同态计算实现了保护隐私的频谱分配。在P2-SAS中，IU和SU仅与SAS服务器共享其操作数据的密文，SAS服务器直接在这些密文上执行安全同态计算，因此IU/SU的操作数据不会暴露给任何侦听方，包括SAS本身。该项目旨在将复杂的频谱分配计算和认证过程转换为高效的Paillier密码系统提供的有限同态计算类型。利用频谱分配计算的独特特性，将探索各种精炼技术，以显着降低P2-SAS的计算和通信开销，并防止对系统的潜在攻击。

Dynamic spectrum access (DSA) technique enables wireless devices, called secondary users (SUs), to use spectrum that are allocated to licensed incumbent users (IUs) as long as they do not interfere with IUs' operation. It has been widely accepted as a crucial solution to mitigate the spectrum scarcity problem for wireless communications. As a key form of DSA, regulators have proposed to release more Federal spectrum for sharing with commercial wireless users, under the umbrella of a spectrum access system (SAS) database to govern the spectrum sharing between IUs and SUs. However, the success of this sharing hinges upon how privacy issues are managed. In current SAS schemes, the operation data of both federal IUs and commercial SUs need to be shared with the SAS database for it to decide if sharing is permitted. Yet, operation data of federal IUs are often classified information and SU operation data may also be commercial secret. Since SAS is not necessarily operated by a trusted third party and can potentially be breached by attackers, these current schemes threaten the privacy of both IUs and SUs. To address this privacy issue, this project develops a privacy-preserving SAS (P2-SAS), which ensures that the SAS system can still accurately decide whether spectrum sharing among IUs and SUs are permitted while it learns nothing about the operation data of IUs and SUs. This project is the first to be able to successfully realize privacy-preserving spectrum allocation in SAS. It addresses regulators' concerns with DSA's privacy issue and hence greatly help the development of the entire nation's broadband networks. The project provides a blueprint on how privacy-preserving mechanisms can be integrated in many other communication systems beyond DSA. The project realizes its privacy preserving spectrum allocation using secure homomorphic computation. In P2-SAS, IUs and SUs share only ciphertexts of their operation data with the SAS Server, which then performs secure homomorphic computation directly over these ciphertexts, so that none of the IU/SU operation data would be exposed to any snooping party, including the SAS itself. The project aims to convert complex spectrum allocation computation and certification procedures into the limited homomorphic computation types provided by efficient Paillier cryptosystems. Leveraging the unique characteristics of spectrum allocation computation, various refining techniques will be explored to significantly reduce the computation and communication overhead of P2-SAS and prevent potential attacks on the system.