Spot me if you can: Uncovering spoken phrases in encrypted VoIP conversations
Charles V. Wright, Lucas Ballard, Scott E. Coull, =46abian Monrose, Gerald M. Masson
May 2008
Abstract
Despite the rapid adoption of Voice over IP (VoIP), its security implications are not yet fully understood. Since VoIP calls may traverse untrusted networks, packets should be encrypted to ensure confidentiality. However, we show that when the audio is encoded using variable bit rate codecs, the lengths of encrypted VoIP packets can be used to identify the phrases spoken within a call. Our results indicate that a passive observer can identify phrases from a standard speech corpus within encrypted calls with an average accuracy of 50%, and with accuracy greater than 90% for some phrases. Clearly, such an attack calls into question the efficacy of current VoIP encryption standards. In addition, we examine the impact of various features of the underlying audio on our performance and discuss methods for mitigation.
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Yes We Can: Uncovering Spoken Phrases in Encrypted VoIP Conversations
Goran Doychev, Dominik Feld, Jonas Eckhardt, Stephan Neumann May 28, 2009
Abstract
The growing importance of VoIP telephony over untrusted networks raises the requirements to encrypt VoIP calls. To achieve a good trade-off between audio quality and network traf=DEc, Variable Bit Rate (VBR) codecs are widely employed. VBR codecs encode speech data at different bit rates depending on the complexity of the input signal. We implemented a practical side channel attack on VoIP applications using VBR codecs associated with length preserving encryption.
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Uncovering Spoken Phrases in Encrypted VOIP Conversations
Trent Kalisch-Smith, Charles V. Wright, Lucas Ballard Scott E. Coull, Fabian Monrose, Gerald M. Masson