本文選題：混沌系統(tǒng) + 自適應(yīng)��； 參考：《安徽大學(xué)》2017年碩士論文

【摘要】：由于Internet的蓬勃發(fā)展,多種多樣的圖形和圖像等多媒體信息在互聯(lián)網(wǎng)絡(luò)上傳播。然而,據(jù)報道世界上每20秒就有一例黑客入侵事件發(fā)生,許多重要的數(shù)據(jù)在信息傳送過程中破損或被竊取。怎樣準(zhǔn)確完整地傳送所有信息是目前網(wǎng)絡(luò)信息中一個急需解決的難題。數(shù)字圖像在多媒體信息中占據(jù)著重要的位置,對圖像進行加密是目前可靠傳輸?shù)闹饕绞�。由于混沌系統(tǒng)的內(nèi)在隨機性和初值敏感性與已有的古典密碼體制的擴散性質(zhì)相契合,因此被廣泛應(yīng)用到圖像加密中。Logistic混沌映射具有復(fù)雜的動力學(xué)行為,其所產(chǎn)生的混沌密鑰序列具有良好的隨機性,可以改變圖像的灰度值,而自適應(yīng)加密算法是以圖像自身的像素對圖像進行排列置亂的加密算法,具有運行速度快、置亂效果好的優(yōu)點,因此較多應(yīng)用于圖像加密中去。本文在深入研究基于混沌理論的圖像加密的基礎(chǔ)上,結(jié)合自適應(yīng)技術(shù),對混沌映射的圖像加密進行了改進。本文的主要工作為以下幾個方面。1.采用了一種兩段式Logistic混沌映射對圖像進行加密。本文在研究多種一維和高維的混沌系統(tǒng)的基礎(chǔ)上,選擇一種對一維Logistic映射進行改進的兩段式Logistic混沌映射,并應(yīng)用在圖像加密中。該兩段式不僅比原有Logistic混沌映射更早進入混沌狀態(tài),而且在很大參數(shù)范圍內(nèi)都達(dá)到滿映射狀態(tài),增大了密鑰空間,增強了一維Logistic混沌映射的抗攻擊性能力。并通過統(tǒng)計分析、相鄰像素的相關(guān)性分析等驗證了該改進加密算法的安全性。2.設(shè)計了一種基于兩段式Logistic混沌映射的自適應(yīng)圖像加密算法。自適應(yīng)算法自提出以來就受到廣大學(xué)者的關(guān)注,它改進了一般排列加密與密鑰無關(guān)的缺點,但是排列加密只改變圖像像素的位置,像素之間的相關(guān)性沒有改變。本文把自適應(yīng)加密算法的排列加密與像素替代相結(jié)合,設(shè)計了一種基于兩段式Logistic映射的自適應(yīng)圖像加密算法,在對圖像分塊后,按照圖像加密順序,用第一個子塊圖像的像素異或值對下面子塊圖像進行加密。在分段Logistic混沌映射的基礎(chǔ)上,通過Logistic映射產(chǎn)生隨機序列并轉(zhuǎn)換成二進制密鑰流,采用主密鑰流對圖像隨機選擇加密順序,子密鑰流選擇對子塊的像素排列與像素替代的混合加密模式。通過實驗仿真和差分性分析、直方圖分析、相關(guān)性分析驗證了算法的安全性。
[Abstract]:With the rapid development of Internet, a variety of multimedia information, such as graphics and images, is spread over the Internet. However, it is reported that there is a hacking incident every 20 seconds in the world, and many important data are broken or stolen in the process of information transmission. How to transmit all information accurately and completely is an urgent problem in network information. Digital image plays an important role in multimedia information. Encryption of image is the main way of reliable transmission. Because the inherent randomness and initial value sensitivity of chaotic systems coincide with the diffusion properties of the existing classical cryptosystems, it is widely used in image encryption. Logistic chaotic mapping has complex dynamic behavior. The chaotic key sequence produced by the algorithm has good randomness and can change the gray value of the image. The adaptive encryption algorithm is an encryption algorithm that arranges and scrambles the image with its own pixels. The effect of scrambling is good, so it is more used in image encryption. Based on the research of image encryption based on chaos theory and adaptive technology, this paper improves the image encryption of chaotic map. The main work of this paper is as follows. A two-segment Logistic chaotic map is used to encrypt the image. In this paper, based on the study of many kinds of chaotic systems of one dimension and high dimension, we choose a two-segment Logistic chaotic map, which can improve the one-dimensional Logistic map, and apply it to image encryption. The two segments not only entered the chaotic state earlier than the original Logistic chaotic map, but also reached the full mapping state in a wide range of parameters, which increased the key space and enhanced the anti-attack ability of the one-dimensional Logistic chaotic map. The security of the improved encryption algorithm is verified by statistical analysis, correlation analysis of adjacent pixels and so on. An adaptive image encryption algorithm based on two-segment Logistic chaotic mapping is designed. The adaptive algorithm has been concerned by many scholars since it was put forward. It improves the shortcomings of general permutation encryption which is independent of the key, but the permutation encryption only changes the location of image pixels, and the correlation between pixels is not changed. This paper combines the arrangement encryption of adaptive encryption algorithm with pixel substitution, and designs an adaptive image encryption algorithm based on two-segment Logistic mapping. Encrypt the subblock image below with the pixel XOR value of the first subblock image. On the basis of piecewise Logistic chaotic mapping, random sequence is generated by Logistic mapping and converted into binary key stream. The subkey stream selects the pixel arrangement of the sub-block and the mixed encryption mode instead of the pixel. The security of the algorithm is verified by experimental simulation, differential analysis, histogram analysis and correlation analysis.
【學(xué)位授予單位】：安徽大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TP309.7;TP391.41

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