在本論文中，我們改進了一種基於位元運算的影像加密演算法，並以Altera FPGA DE2-115實現完整的加密與傳輸系統，並透過FPGA的流水線特性對其進行計算上的優化。
我們使用了三維渾沌系統來產生加密過程中所需要的金鑰，在我們的加密演算法中，一共有兩個特色。第一，我們透過自己設計的演算法來對現有的像素打散演算法進行優化，使其具有更好的通用性；第二，我們針對一般加密演算法常使用的互斥或方法進行優化，並利用FPGA設計對應的電路，透過FPGA高度平行化與流水線的特性，可以將演算法的效能提高非常多。在加密安全性分析中，我們除了常用的直方圖分析、相關性係數分析、熵值分析和差異性分析以外，還引入了區域性熵值分析，透過自己設計的實現方法進一步驗證我們加密的效果。從以上分析可以知道，我們所設計的影像加密演算法除了有高通用性，並同時具有高效能的優點，十分適合應用於現有系統中。

In this thesis, we improved a bitwise-based image encryption algorithm and implemented a encryption and transmission system with Altera FPGA DE2-115, and optimized it through FPGA's pipeline feature.

We use a three-dimension chaotic system to generate the keys needed for the encryption process. There are two features in our encryption algorithm. First, we proposed an algorithm to improve the existing permutation algorithm to make it more in common use. Second, we optimize the XOR methods used in ordinary encryption algorithms. Use FPGA to design the corresponding circuit, through the highly parallelized and pipelined feature of FPGA, It can improve the efficiency of the algorithm a lot. In the analysis of cryptographic security. We used histogram analysis, correlation coefficient analysis, entropy analysis, and variance analysis, Besides, we also introduced local entropy analysis to verify the effectiveness of our encryption algorithm. Through we proposed an implementation method of the local entropy algorithm. From the above analysis, we can know that the image encryption algorithm we designed is not only highly versatile, but also has the advantages of high performance, and is very suitable for application in realistic systems.

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