Covert Channels in SIP for VoIP signalling

TL;DR

This paper evaluates and introduces steganographic techniques for SIP in VoIP, analyzing their capacity for covert data transfer during call signaling, with new insights into method effectiveness and data capacity.

Contribution

It characterizes existing SIP steganography methods, introduces new techniques, and estimates their data transfer capacity during VoIP call signaling.

Findings

Existing methods vary in data hiding capacity.

New techniques improve covert channel robustness.

Estimated data transfer per signaling message is quantified.

Abstract

In this paper, we evaluate available steganographic techniques for SIP (Session Initiation Protocol) that can be used for creating covert channels during signaling phase of VoIP (Voice over IP) call. Apart from characterizing existing steganographic methods we provide new insights by introducing new techniques. We also estimate amount of data that can be transferred in signalling messages for typical IP telephony call.