Eavesdropping on Encrypted Compressed Voice

Traffic analysis works even through the encryption:

The new compression technique, called variable bitrate compression produces different size packets of data for different sounds.

That happens because the sampling rate is kept high for long complex sounds like “ow”, but cut down for simple consonants like “c”. This variable method saves on bandwidth, while maintaining sound quality.

VoIP streams are encrypted to prevent eavesdropping. However, a team from John Hopkins University in Baltimore, Maryland, US, has shown that simply measuring the size of packets without decoding them can identify whole words and phrases with a high rate of accuracy.

The technique isn’t good enough to decode entire conversations, but it’s pretty impressive.

Written by admin

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.