Whisper: a unilateral defense against VoIP traffic re-identification attacks
Whisper: a unilateral defense against VoIP traffic re-identification attacks
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DOI：
10.1145/3359789.3359807
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发表时间：
2019-12
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影响因子：
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通讯作者：
Tavish Vaidya;T. Walsh;M. Sherr
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文献类型：
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作者：
Tavish Vaidya;T. Walsh;M. Sherr
加密的IP语音（VoIP）通信通常使用可变比特率（VBR）编解码器来实现良好的音频质量，同时最小化带宽成本。先前的工作已经表明，加密的基于VBR的VoIP流容易受到重新识别攻击，其中攻击者可以推断属性（例如，所讲的语言、说话者的身份和关键短语）。现有的防御需要发送方和接收方的参与，以保护他们的VoIP通信。本文介绍了Whisper，第一个单方面防御加密VoIP流上的重新识别攻击。Whisper的工作原理是在VBR编解码器对音频信号进行编码之前对其进行修改，添加福尔斯不在人类听觉固定范围内或在人类听觉范围内但由于其低振幅而几乎无法感知的听不见的音频。通过小心地插入这样的噪声，Whisper修改了音频流的数据包大小分布，显著降低了重新识别攻击的准确性。它的使用是不可察觉的（人类）接收器。Whisper可以作为音频驱动程序进行仪表化，并且不需要对现有（可能是闭源）VoIP软件进行更改。由于它是一种单方面的防御，它可以由用户随意应用，以增强其语音通信的隐私。我们证明了Whisper显著降低了重新识别攻击的准确性，并且只会导致音频质量的小幅下降。
Encrypted voice-over-IP (VoIP) communication often uses variable bit rate (VBR) codecs to achieve good audio quality while minimizing bandwidth costs. Prior work has shown that encrypted VBR-based VoIP streams are vulnerable to re-identification attacks in which an attacker can infer attributes (e.g., the language being spoken, the identities of the speakers, and key phrases) about the underlying audio by analyzing the distribution of packet sizes. Existing defenses require the participation of both the sender and receiver to secure their VoIP communications. This paper presents Whisper, the first unilateral defense against re-identification attacks on encrypted VoIP streams. Whisper works by modifying the audio signal before it is encoded by the VBR codec, adding inaudible audio that either falls outside the fixed range of human hearing or is within the human audible range but is nearly imperceptible due to its low amplitude. By carefully inserting such noise, Whisper modifies the audio stream's distribution of packet sizes, significantly decreasing the accuracy of re-identification attacks. Its use is imperceptible by the (human) receiver. Whisper can be instrumented as an audio driver and requires no changes to existing (potentially closed-source) VoIP software. Since it is a unilateral defense, it can be applied at will by a user to enhance the privacy of its voice communications. We demonstrate that Whisper significantly reduces the accuracy of re-identification attacks and incurs only a small degradation in audio quality.