JoWUA

Abstract

Fountain codes are used to provide reliable communication over a lossy network with low overhead and without acknowledgment. We present a method for network steganography within a fountain code as carrier, which uses most carrier packets to transmit parts of the secret message, and tries to maximize bandwidth. As also parts of the secret message get lost when a carrier packet is lost, reliable transmission of the secret message is provided by using a second fountain code. Thus, our proposal opens the possibility for a multilevel steganographic method. We provide a detailed analysis on the possible bandwidth in multiple levels and a complete implementation for Luby Transform (LT) codes which we evaluate with a focus on detectability, i.e., if random values in a carrier packet can be distinguished from secret message parts. We also discuss countermeasures that limit the possibilities for covert channels in fountain codes.