Analysis And Design Of Security Mechanisms Of Wireless Communications In Random Channels

With the extensive application of wireless communications, security issues in theopen wireless channel have been paid more and more attention. By using the methodsin both physical layer security and modern cryptography, we understood deeply securityissues in wireless communications, to analyze and design block ciphers, stream ciphersand authentication mechanisms in this thesis.First, for the absence of in-depth understanding about the security issues in wirelesscommunications from a systematic perspective, we proposed a framework to quantita-tively evaluate the system security of a class of wireless transmission mechanisms. Byusing linear cryptanalysis, which is one of the classical cryptanalysis methods in moderncryptography, the system security is described as the difculty of eavesdropping underthe influence of channel coding and channel randomness. The framework can reveal therelevance and diference between the system security of wireless communications and thesecurity of cryptographic algorithms.Second, by analyzing the impact of channel randomness, we quantitatively charac-terized the tradeof between security enhancement and information transfer rate degra-dation. To understand the impact of the wireless channel on the system security andinformation transfer rate, we used a class of model which consists of a systematic linearblock code and encrypted nonlinear mappings. Our model has wider applicability thanthe existing model, which consists of an RS code and Sboxes of AES.Third, with a detailed consideration of channel randomness, we proposed a new ap-proach to design physical layer block encryption mechanisms for wireless transmission.It is diferent from the traditional method, in which the channel coding provides an idealequivalent channel to the block cipher. This new approach puts the block cipher in thephysical layer, and makes use of the efects of channel coding and channel randomness.Our analysis shows that the system security could be improved with high level channelrandomness.Fourth, while understanding about the error propagation in stream ciphers, we quan-titatively characterized the law of error propagation in an OCOML stream cipher, anddesigned a double-coupled drivers system. While the previous studies emphasized theenhancement of system security, our work considered the impact of channel randomness on error propagation. Numerical analysis shows that the proposed system can efectivelyimprove the information transfer rate.Fifth, we investigated the number of ordinal patterns in both piecewise monotonemappings and a kind of OCOML models, and the robustness of ordinal pattern probabilitycharacteristics against observation noise. While explorating the channel characteristicsunder the influence of noise, we proposed a preliminary method to improve the temporalchannel impulse response by making use of ordinal patterns. Numerical analysis showsthat the authentication accuracy might be improved at the low SNR.Generally, our work may contribute to deepen the understanding of security issuesin wireless communications, and may promote the theoretical study and practical appli-cation of security mechanisms under the influence of the open wireless channel.