No abstract

Voice over Long-Term Evolution enables reliable transmission among enormous Internet of Things devices, by providing end-to-end quality of service for Internet protocol-based services such as audio, video, and multimedia messaging. The research of covert timing channels aims at transmitting covert message stealthily to the receiver using variations of timing behavior. Existing approaches mainly modulate the covert message into inter-packet delays of overt traffic, which are not suitable for Voice over Long-Term Evolution, since most of the inter-packet delays of Voice over Long-Term Evolution traffic are of regular distribution, and any modification on inter-packet delays is easy to be detected. To address the issue, in this work, we propose a novel covert timing channel for the video stream in Voice over Long-Term Evolution, which modulates the covert message by deliberately dropping out video packets. Based on the twodimensional mapping matrix, the blocks of covert message are mapped into dropout-packet sequence numbers. To recover the covert message, the receiver retrieves the sequence numbers of lost packets and identifies them to be translated into blocks of the covert message. To evaluate our scheme, the simulations with different packet loss rates are conducted to validate the undetectability, throughput, and robustness, finally, the results show that this scheme is effective and reliable.

Covert communication in this regard has been widely used for protecting the secrecy of communication.Voice over Long Term Evolution (VoLTE) is a packetswitched core network solution for high-speed and high-quality end-to-end services which usually applied to the communication between intelligent systems. However, covert channels using inter-packet delays and packet order in VoLTE services are limited by specific rules. Since minor modifications to overt traffic can be detected, existing covert channel solutions cannot be directly applied to VoLTE. Therefore, this study presents a robust packet loss covert timing channel by cascade hash coding with intelligent system. To ensure robustness and undetectability, we design hash-based inter-codeword verification, codeword self-verification based on cyclic redundancy check, and adaptive mapping matrix. The sender modulates the covert messages according to the sequence number of the actively dropped packets, and the receiver can retrieve the covert messages using a specialized verification method. To evaluate undetectability, robustness, throughput, and construction costs, a large number of experiments in mobile intelligent terminals have been conducted. The experimental results prove that the proposed scheme is feasible for VoLTE communication, as the covert message is