Research On Key Technologies Of Physical Layer Security Based On Fountain Code

With the rapid development of wireless communication technology,mobile smart terminals have exploded in recent years while wireless channels are vulnerable to illegal party attacks due to their natural openness.Traditional high-level security methods rely on upper-level authentication and encryption technologies to achieve this,and traditional security mechanisms are facing challenges in the face of super-strong quantum computing capabilities and diverse business scenarios.The independent fading characteristics of wireless channels make user channels irreproducible to illegal parties,and Physical Layer Security（PLS）technology cleverly exploits the endogenous security properties of wireless channels to provide a new vision for solving the openness problem of wireless communication.In this thesis,physical layer security transmission techniques are studied for the characteristics of wireless channels,which can be used as a complementary means to the high-level security methods,and the main work is as follows.The thesis investigates the basic principle of Maximum Distance Separable（MDS）codes,followed by the confidential transmission technique using MDS codes without feedback.The theoretical analysis and numerical simulation prove that the decoding success probability of both the receiver and the eavesdropper decreases due to the increase of packet length and the increase of packet loss,so joint success probability can be maximized by optimizing the encoding package length.The thesis analyzes the confidential transmission technique using MDS codes with feedback.The numerical simulation results verify that the feedback information can stop the packet transmission in time when the receiver succeeds in decoding and reduce the additional information leakage,so it improves the confidential transmission performance compared with the nofeedback scheme.The thesis investigates the degree distribution function of fountain codes and the principle of encoding and decoding.The thesis studies the confidential transmission technique based on fountain codes under single-channel transmission conditions.The fountain code is a rateless code,which also increases the risk of information leakage while ensuring reliable transmission from the receiver.The thesis further investigates the confidential transmission technique under multi-channel transmission conditions,which can better reduce the interception probability of the eavesdropping party because the multi-channel speeds up the packet reception rate of the receiver.The thesis establishes an optimization model around resource allocation for the multi-channel confidential transmission scheme.Under the condition that the eavesdropping party randomly listens to some channels with a certain probability,the thesis obtains the maximization of the overall energy efficiency of the system by optimizing the transmission block number and power allocation of each channel with the premise of service delay demand and confidentiality performance.The thesis investigates the fountain code technique based on symmetric encryption,where the sender uses a random key to protect the source file.Due to the independence of channel fading,there is a difference in channel quality between the receiver and the eavesdropper,and thus a difference in the correctness of the received data.The encrypted random key can be transmitted between the sender and the receiver based on the handshake of the correctly received data,then the receiver can correctly recover the source file.The thesis further investigates the fountain code technique based on interlocking encryption,where the sender encrypts the encoding rules of the fountain code generation matrix based on the correct received packet sequence number information fed back to it by the receiver.This scheme introduces a key encryption feedback link based on channel characteristics,so that the receiver can reconstruct the encoding matrix and decode the fountain successfully,while the interception probability of the eavesdropping party will be effectively suppressed.The numerical simulation results show that the interlocking encryption technique achieves the implicit transmission of the coding matrix and better confidential transmission than the symmetric encryption technique.