本文中，我們提出三種方法來建構渾沌密碼系統，第一個是時空擾動法(spatial-temporal perturbation method)，
第二個是延長斜logistic映射(extend-skew logistic map)，
第三個是結合時空擾動法與延長斜logistic映射的特性及高效能輸出策略來建構的渾沌密碼流。

時空擾動法是時間擾動法(temporal perturbation method)的一種推廣。時間擾動法是利用一維渾沌映射的延遲變量所組合成的偽隨機數，
用來擾動渾沌映射本身，並改善渾沌映射在有限計算精度的數位電腦上實現所產生的動態退化的問題。
由於延遲變量是渾沌映射自身產生不需額外計算而且其偽隨機數的更新(update)，只需做位元平移運算，
因此時間擾動法只需增加一些暫存器(registers)，來儲存本身所產生的偽隨機數，雖只增加了位元平移與xor兩種運算，
但所改善的效果卻相當驚人，可使渾沌映射的週期和狀態使用率大幅增加，因此時間擾動法是個快速、成本低且有效的方法。
我們將時間擾動法運用在logistic 映射上，形成偽隨機數生成器TPLogist($m,l,q$)，其中$m$為計算精度，$l$為延遲因子長度，
而$q$為輸出的位元數，TPLogist($m,l,q$)不僅通過了美國國家標準局(NIST) SP800-22和TestU01兩種統計測試軟體，
而且也實作了硬體晶片來驗証其有相當好的效能；另外，時空擾動法是為了將多個渾沌映射結合成一個渾沌系統所產生的一種方法，
此方法是將每一個渾沌映射所產生的偽隨機數來擾動其鄰近的渾沌映射，它不僅繼承了時間擾動法的快速、成本低、高效能等特性，
還能增強渾沌映射之間的關連性並提供簡單快速的擴充性，可提供較大的參數空間來增強之後建構密碼系統的安全性。

由於目前常用於渾沌密碼的渾沌映射是帳篷映射(tent map)、分段線性渾沌映射(piecewise linear chaotic map)和logistic 映射，
而前兩者是類線性的，較容易被分析出它的參數而影響渾沌密碼的安全性，而後者雖然是非線性的，但它的分佈是非均勻的，
且參數有渾沌空窗(chaotic windows)的現象，這容易造成在應用於渾沌密碼的安全性與效能降低，
因此我們提出一個新的渾沌映射-延長斜logistic映射，不僅可提升渾沌密碼的安全性，並且有較高的效能，
因為延長斜logistic 映射有非線性、均勻分佈、兩個控制參數、高複雜性和不易被分析等特性，因此非常適合運用在渾沌密碼。

一般來說，密碼系統的安全性與效能是難以兼顧的。因為若要有較高的安全性，勢必要有更多、更複雜的計算來達成，但其效能就會下降；
相反的，如要提升效能，其安全性就會降低，或者是需要增加硬體成本。因此如何在安全性、效能與成本間取得平衡，
即為渾沌密碼系統是否能真正應用於現實社會的一個重要課題。而最後我們結合時空擾動法和延長斜logistic映射的特性，
並提出一個兼顧安全性與效能輸出策略，來建構一個速度快、安全性高且硬體、成本低的渾沌密碼，並提出一些對渾沌密碼系統的未來展望，
它能實際應用於網路通訊、無線通訊和軍事保密上。

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