Analysis of the tradeoff between compression ratio and security level in real-time voice communication

Abstract

This paper presents an analysis of the tradeoff between security level and compression ratio in real-time voice communication. It is hypothesized that the combination of variable bitrate compression and same length encryption will induce vulnerability to traffic analysis. The variation of packet sizes can leak information about the conversation starting with language identification, identifying certain phrases, and reconstructing phonemes. The proposed solution to this problem is to rely on constant bitrate compression or to pad the sent frames to a multiple of 16, 32, or 64 bytes.