TC: Small: Exploring Privacy Breaches in Encrypted VoIP Communications

在过去的几年里，IP语音（VoIP）的普及程度显著提高，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拥有数百万用户。与此同时，通过互联网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。在大多数情况下，目前对VoIP安全的关注集中在强化信令协议上。最近，围绕VoIP通信的窃听和呼叫劫持威胁的关注度越来越高，这使得在通过互联网传输VoIP数据之前需要对其进行加密。 不幸的是，目前加密VoIP流量的建议是为了效率而不是隐私。在这个项目中，我们探讨了在VoIP中使用可变比特率编码器（以节省带宽）和流密码（保密）的常见做法下出现的风险。 我们的最终目标是更好地了解VoIP使用的各种隐私威胁，并探索阻止这些违规行为的对策。 我们还探讨了与平衡隐私和效率的更好方法相关的权衡，着眼于最大限度地减少对VoIP呼叫感知质量的影响。这项工作更广泛的意义是提供合理的设计，有利于更大的网络社区正在进行的努力，以确保VoIP。

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.