TC: Small: Exploring Privacy Breaches in Encrypted VoIP Communications

在过去的几年中，IP语音(VoIP)得到了显著的普及，特别是作为国际电话的传统电话的替代品。事实上，几家大型网络提供商已经号称拥有数百万用户。与此同时，在互联网上进行日常语音通信的安全和隐私影响尚未得到很好的理解。在很大程度上，目前对VoIP安全的关注集中在加强信令协议上。最近，对VoIP通信的窃听和呼叫劫持威胁的关注增加了在通过互联网传输VoIP数据之前对其进行加密的需求。遗憾的是，当前的VoIP流量加密建议都是针对效率而非隐私进行调整的。在本项目中，我们将探讨在使用可变比特率编码器(以节省带宽)和流密码(出于保密性)的常见实践下，VoIP中出现的风险。我们的最终目标是更好地了解VoIP使用面临的广泛隐私威胁，并探索阻止这些违规行为的对策。我们还探讨了与更好地平衡隐私和效率的方法相关的权衡，着眼于将对VoIP呼叫的感知质量的影响降至最低。这项工作的更广泛的意义是提供有利于更大网络社区保护VoIP的持续努力的合理设计。

Over the last several years, Voice over IP (VoIP) has enjoyed a marked increase in popularity, particularly as a replacement of traditional telephony for international calls. Indeed, several large network providers already boast millions of subscribers. At the same time, the security and privacy implications of conducting everyday voice communications over the Internet are not yet well understood. For the most part, the current focus on VoIP security has centered around hardening the signaling protocol. Of late, the increased attention surrounding eavesdropping and call hijacking threats to VoIP communications has heightened the need for encrypting VoIP data before transmitting it over the Internet. Unfortunately, the current recommendations for encrypting VoIP traffic are tuned for efficiency rather than privacy.In this project, we explore the risks that arise in VoIP under the common practice of using variable bit rate encoders (to save bandwidth) and stream ciphers (for confidentiality). Our ultimate goals are to better understand a wide spectrum of privacy threats to VoIP usage, and to explore countermeasures to hinder these breaches. We also explore the trade-offs associated with better ways of balancing privacy and efficiency, with an eye towards minimizing the impact on the perceptual quality of VoIP calls. The broader significance of the work is to provide sound designs that benefit ongoing efforts in the greater networking community to secure VoIP.