A Timestamp-Regulating VoLTE Covert Channel against Statistical Analysis

Covert channels are widely used for secret message transmission on networks, and they are constantly changing and updating to adapt to the new network and communication environment. There are a large number of video packets during VoLTE (Voice over LTE), which can be a suitable carrier for covert channels. In this paper, we design a secure covert storage channel for VoLTE via regulating timestamp of VoLTE packets. First, we analyze the data captured in the real environment and find out two statistical patterns for the timestamp of the video packets. Then, we build the covert channel by modifying timestamp to carry the covert message in the case of maintaining these two patterns. Finally, we simulated the covert channel using the data captured in the real environment. Experimental results show that the covertchannel can communication over VoLTE secretly and robustly with bit-rate up to 120 bit/s, and it is against statistical analysis such as the Kolmogorov-Smirnov(KS) test and linear regression.