Date Added: Mar 2010
In this work the authors propose a Voice over IP (VoIP) call tracking scheme based on robust hashing of VoIP flows. In the proposed scheme the audio content of a possibly encrypted VoIP flow is identified by a short binary string, called the robust hash, using variations on the flow's bitrate over time. These robust hashes are then used to detect pairs of parties communicating with each other. In summary, if two parties are communication with each other then they have a pair of VoIP flows having similar robust hashes with high probability.