| Summary: | 碩士 === 國立成功大學 === 電腦與通信工程研究所 === 106 === In communication networks, security is traditionally divided into three categories: integrity, confidentiality and availability. Potentially, optical code-division multiple-access (OCDMA) system may provide both confidentiality and availability protection. Therefore, OCDMA has been seen as a superior candidate to offer confidentiality. However, OCDMA techniques still suffer from inherent security disadvantages, such as eavesdropping by an attacker with specific device to intercept and recover the transmitted signals that has been encoded.
In this thesis, a scheme of signature code reconfiguration over OCDMA network is proposed to enhance multiple-users data transmission security. The security scheme is devised on the basis of two mechanisms: (1). Eavesdropping detection based on power comparison in local node; (2). Signature codes reconfiguration in each node on command of central control station. On eavesdropping detection, we sense significant power change while communicating nodes pair is suffering malicious attack. On signature reconfiguration, central station sends commands to the communicating transceiver nodes to change their signature keys.
We illustrate with maximal-length sequence (M-sequence) codes as signature keys to the network nodes. These signatures are structured over arrayed-waveguide gratings (AWGs) devices. Simulation result shows that the spectral amplitude drops obviously after eavesdropping and the threshold value can be determined in order to detect the eavesdropping effectively. Also, the result of the analysis on eavesdropping probability shows that the confidentiality performance is significantly enhanced when considering the proposed eavesdropping detection on signature reconfiguration.
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