Multi-class Traffic Morphing for Encrypted VoIP Communication

In a re-identification attack, an adversary analyzes the sizes of intercepted encrypted VoIP packets to infer characteristics of the underlying audio—for example, the language or individual phrases spoken on the encrypted VoIP call. Traffic morphing has been proposed as a general solution for defending against such attacks. In traffic morphing, the sender pads ciphertext to obfuscate the distribution of packet sizes, impairing the adversary’s ability to accurately identify features of the plaintext.