Spot Me if You Can: Uncovering Spoken Phrases in Encrypted VoIP Conversations
- 1 May 2008
- conference paper
- conference paper
- Published by Institute of Electrical and Electronics Engineers (IEEE) in 2008 IEEE Symposium on Security and Privacy (SP 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.Keywords
This publication has 22 references indexed in Scilit:
- Multi-band speech recognition in noisy environmentsPublished by Institute of Electrical and Electronics Engineers (IEEE) ,2002
- Recognizing voice over IP: a robust front-end for speech recognition on the world wide webIEEE Transactions on Multimedia, 2001
- HMM-based word alignment in statistical translationPublished by Association for Computational Linguistics (ACL) ,1996
- A robust algorithm for word boundary detection in the presence of noiseIEEE Transactions on Speech and Audio Processing, 1994
- Hidden Markov Models in Computational Biology: Applications to Protein ModelingJournal of Molecular Biology, 1994
- QCELP: A Variable Rate Speech Coder for CDMA Digital CellularPublished by Springer Science and Business Media LLC ,1993
- Automatic recognition of keywords in unconstrained speech using hidden Markov modelsIEEE Transactions on Acoustics, Speech, and Signal Processing, 1990
- A tutorial on hidden Markov models and selected applications in speech recognitionProceedings of the IEEE, 1989
- Optimization by Simulated AnnealingScience, 1983
- A Maximization Technique Occurring in the Statistical Analysis of Probabilistic Functions of Markov ChainsThe Annals of Mathematical Statistics, 1970