Research On Key Technologies Of Information Steganography And Transmission Based On Fixed Codebook In Mobile Voice Channel

With the rapid development of mobile communication networks and the popularity of smart phones,the scale of users of voice channels is also rapidly expanding,which brings many conveniences and is accompanied by huge information security issues.How to ensure the safe transmission of information in voice channels has become a hot issue for scholars at home and abroad.As an interdisciplinary subject of data transmission and information security,information steganography can use audio,video or images as carriers to transmit secret information and avoid third-party attention or theft,which has very important research significance.Firstly,this thesis introduces the system models of ideal voice channel and actual voice channel,and analyzes in detail the possible technical difficulties in actual transmission and three evaluation indicators used to evaluate the performance of the algorithm.Secondly,according to the actual situation,this thesis designs a highly robust and imperceptible information steganographic algorithm,a fast synchronization algorithm based on the steganography algorithm,and an extraction algorithm that can be applied to actual transmission.The main innovations and research results of this thesis are as follows:1.In the past,all of the information steganography algorithm based on AMR-WB vocoder fixed codebook is designed for the scene of simulation or ideal channel.The steganography algorithm proposed in this thesis is aimed at the actual transmission scene that needs to be coded and decoded many times and faces many kinds of interference.With this algorithm,In the process of fixed codebook standard search,multiple pulses can be modified without damaging the basic structure of the voice,and the modified pulses can be set to the aggregated distribution to enhance robustness.The simulation results show that under the condition of ensuring the steganography capacity,this algorithm can not only resist various interferences in the channel and accurately transmit secret information,but also pass the test of voice detection and noise suppression modules and maintain good sound quality.2.After a detailed study of the out-of-step characteristics of fixed codebooks at various levels under simulation scenario,this thesis designs a fast synchronization algorithm based on the proposed steganography algorithm to find synchronization sequences.The experimental results show that it can significantly reduce the number of encoding times while ensuring accuracy to meet real-time requirements.On the other hand,in response to the problem of out of step in actual transmission,this thesis proposes an improved information extraction algorithm that can effectively find the steganographic position to overcome the impact of synchronization drift.The actual test results show that the combination of the two algorithms can accurately decode the secret information,and achieve high robustness and high imperceptibility of transmission.