應用數位訊號處理器於影像加密解碼之研究

研 究 生：劉楷哲
指導教授：楊世銘

摘 要

數位影像是非常普遍的影像儲存型態，由於資訊科技的發展，航太系統之數位通訊已漸成主流，而數位影像通訊更為下世代CNS/ATM等導航系統之發展重點。本文提出數位影像加密解碼架構，整合 (1) 離散餘弦轉換， (2) 可調整式量化表， (3) 中頻係數選取於數位訊號處理器，加快處理離散餘弦轉換與量化的動作，實現數位影像之即時加密與解碼，以期此架構可快速導入航空電子系統之數位通訊。此架構並成功地推展至彩色影像的加密解碼，相信在未來的應用將更廣也更有效率。

DEVELOPMENT OF IMAGE ENCYPTION AND DECODING
BY USING DIGITAL SIGNAL PROCESSOR

Student: Kai-Che Liu
Advisor: Shih-Ming Yang

Abstract

The advent of digital communication in aerospace is driving the safety issues of transmitting digital images. The thesis proposes an algorithm of digital image encryption/decoding by using discrete cosine transform. The algorithm integrates the discrete cosine transform, the selection of middle-frequency ranges and the adjustment of quantization table such that a digital watermark can be efficiently and effectively embedded to satisfy all the requirements of digital image encryption/decoding. The table can increase the quality of encrypted image and decrease the memory size of a gray-level watermark. Experimental verification on data transmission loss, image sabotage and compression/decompression are also presented to evaluate the robustness of the algorithm. The algorithm of digital image encryption/decoding is also successfully implemented in digital signal processor. Experiments show that encryption/decoding can be completed within 1 second and the quality of image remains distinct. In addition, the algorithm is extended from gray-level image to true color image for engineering applications.

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