Research On Key Technologies Of Covert Communication Based On Audio In Air-Gapped Environment

While smart devices bring convenience to people,they also bring a lot of security problems.The traditional view is that systems in an air-gapped environment are relatively safe,but with the development of technology,this protection is also facing new threats.As an important part of information hiding technology,audio steganography has developed rapidly in recent years.At the same time,acoustic covert channels are an important way to break through air-gapped.Therefore,it is of great significance to study the audio-based covert communication methods in air-gapped environment.In this paper,based on the air-gapped environment,audio steganography is the main research object.From the practical application point of covert communication,three kinds of audio steganography technologies with real-time,strong robustness and large capacity compression domain are proposed..Meanwhile,an audio steganography program based on inaudible frequency is designed and implemented.The main work of the paper is as follows:(1)The basic theories such as audio steganography general model,human auditory system,digital features of audio signals and steganographic evaluation indicators are in-troduced.The existing audio steganography algorithms are sorted and summarized,and the advantages and disadvantages of the methods are analyzed.(2)Using the characteristics of frequency shift keying easy to implement,the audio time domain and transform domain characteristics are analyzed,and the signal is modu-lated in the frequency band of 8k Hz-20k Hz,realizing the audio steganography algorithm with real-time codec.(3)Based on the stability of centroid,a robust adaptive audio steganography based on wavelet domain centroid is proposed.(4)Using the choice of Huffman table in MP3 compression process,a compressed domain MP3 reversible audio steganography based on Huffman coding is proposed.(5)Based on the characteristics of 18 k Hz-20k Hz frequency range,the human ear is inaudible but the speaker and microphone can support.A real-time covert communication program based on inaudible frequency is designed and implemented.