A stealthy covert storage channel for asymmetric surveillance VoLTE endpoints

The widely adaptation of shared or public cloud computing raises an amount of concerns about privacy and information security. Establishing a covert channel is a feasible solution to the problem by hiding privacy data into the overt packets, so that network information eavesdropping will not detect the existence of user's privacy data transmission. Enormous amount of VoLTE traffic makes it potentially available for stealthy message transfer. A novel covert storage channel based on RTCP (Realtime Transport Control Protocol) is proposed. Based on the analysis of the protocol and real VoLTE traffic data, the secret data is modulated by setting the jitter, or EHSNR(Extended Highest Sequence Number Received) and BLP (Bitmask of following Lost Packets) fields of the RTCP protocol, according to that the sender's network packets are captured by the ward or not. The undetectability of the proposed covert channel is verified by the K-S test (Kolmogorov–Smirnov test) under adversary transmission model.