The Design And Application Of Acoustic Covert Communication System

With the progress of society and the development of science and technology,mobile devices such as laptops and smart terminals are becoming more and more popular,and people are paying more and more attention to information security protection.It has been traditionally thought that network connection is a necessary condition for computers or other devices to be attacked.When the network is disconnected,its data information is relatively safe.But information security protection is a game process,which will continuously meet new challenges.For example,the covert communication established by high frequency acoustic wave is an unconventional security attack technique,which can carry out covert data transmission between air-gapped devices without being detected by the device user.This research object of this thesis is a covert communication technology based on high frequency acoustic wave,which can be used in the field of information security,and can also be used as a method of short-range communication between devices.The key point of this research is to design and realize the scheme of communication between devices using the high frequency acoustic wave in a lower signal to noise ratio and the applications in the actual scenes.The main work is as follows:(1)By studying the transmission characteristics of high frequency acoustic waves in the air,the frequency response curve of the built-in audio processing equipment of normal computer and human ear curve,the necessary preparations for the design of acoustic communication were made.(2)The structure of the acoustic communication system was studied and selected.Point to point one-way communication scheme was designed and implemented by Matlab and MFC respectively,and the performance data of the scheme was given.(3)Aiming at the limitation of point-to-point communication scheme,two improved schemes(two-way communication scheme and variable bandwidth communication scheme)were proposed,and the corresponding realization or simulation was also given;(4)The applications of acoustic communication were also discussed,and the application of the key-logger transmission between the notebooks and the information transmission between the Android mobile phones were realized.Through the design and implementation of the acoustic communication scheme in this thesis,we can know that communication between air-gapped devices can be accomplished through the acoustic waves.At the same time,because of the insensitivity of the ear to the high frequency acoustic waves,if high frequency acoustic waves are used to communicate between devices,it can achieve the effect of covert information transmission,especially suitable for the application of the scene such as close meeting.In addition,the acoustic communication among the mobile devices is simple and does not require additional hardware support,which makes acoustic communication has a chance to become a short-range communication scheme and widely used.