【摘要】：圖像是互聯(lián)網(wǎng)上最主要的一種多媒體元素,政治、經(jīng)濟(jì)、國(guó)防、軍事等方面均在廣泛應(yīng)用圖像信息。在傳輸和使用圖像過(guò)程中,國(guó)防、軍事等應(yīng)用領(lǐng)域均對(duì)圖像內(nèi)容的安全性有一定要求,迫切需要可靠安全技術(shù)以保證傳輸圖像安全。針對(duì)這一方面的需求,研究人員提出了多種技術(shù)手段,其中圖像加密便是一種行之有效的方案。圖像加密又稱圖像置亂,是將一幅有意義的圖像轉(zhuǎn)換成一幅雜亂無(wú)章的圖像,由于攻擊者無(wú)法從雜亂無(wú)章的圖像中獲取有意義信息,從而保證圖像信息的安全。 本文以隨機(jī)分塊策略和混沌技術(shù)為主要切入點(diǎn),研究新型圖像加密算法,設(shè)計(jì)出三種有效的加密算法,取得了有意義的研究結(jié)果。論文先回顧了圖像加密的發(fā)展現(xiàn)狀,在此基礎(chǔ)上,提出聯(lián)合交換技術(shù)和隨機(jī)分塊的快速圖像加密算法、基于塊置亂和混沌映射的圖像加密算法和基于混沌的多圖像加密算法,具體研究結(jié)果如下。 1.提出聯(lián)合交換技術(shù)和隨機(jī)分塊的快速圖像加密算法 該算法先用隨機(jī)分塊技術(shù)將圖像分為四個(gè)重疊的圖像塊,再用密鑰確定圖像塊的加密次序,最后依次運(yùn)用像素交換技術(shù)對(duì)每個(gè)圖像塊加密并將計(jì)算結(jié)果寫(xiě)回圖像。理論分析和實(shí)驗(yàn)結(jié)果表明,該算法可對(duì)任意大小圖像實(shí)行有效加密,具有較好的安全性和魯棒性。與經(jīng)典Arnold變換相比,該算法的運(yùn)行速度更快,安全性更高,應(yīng)用范圍更廣。 2.提出基于圖像塊置亂和混沌映射的圖像加密算法 該算法先將輸入圖像隨機(jī)分割成相互重疊的圖像塊,通過(guò)隨機(jī)置亂圖像塊的位置達(dá)到對(duì)圖像的初始加密,接著利用混沌映射和Arnold變換生成一系列安全的秘密矩陣,最后隨機(jī)選擇秘密矩陣與圖像塊進(jìn)行異或操作,實(shí)現(xiàn)最終加密目的。實(shí)驗(yàn)結(jié)果表明,該算法運(yùn)行速度快,安全性高,性能優(yōu)于三種文獻(xiàn)算法。 3.建立基于混沌映射的多圖像加密算法 針對(duì)多圖像加密問(wèn)題,研究了一次操作完成三幅圖像加密的安全技術(shù)。該算法將三幅同尺寸的灰度圖像看作一幅彩色圖像的三個(gè)顏色分量,先用混沌技術(shù)生成安全的安全數(shù)據(jù)序列,接著與灰度圖像進(jìn)行異或計(jì)算,完成單幅圖像的初始加密,然后將三幅初始加密圖像拼接成一幅大圖像,用交換技術(shù)打亂大圖像中的像素位置,從而將三幅灰度圖像的像素隨機(jī)分布到彩色圖像的三個(gè)分量中,最后將三幅加密圖像組合成彩色圖像即可完成加密目的。實(shí)驗(yàn)結(jié)果表明,該算法可將尺寸相同的三幅灰度圖像轉(zhuǎn)換成一幅安全的彩色秘密圖像,加密后的圖像文件大小比加密前的圖像文件總?cè)萘恳?性能優(yōu)于傳統(tǒng)Arnold變換方法。
[Abstract]:Image is one of the most important multimedia elements on the Internet. Image information is widely used in politics, economy, national defense, military and so on. In the process of image transmission and use, the security of image content is required in the fields of national defense, military and other applications. Therefore, reliable security technology is urgently needed to ensure the security of image transmission. In response to this need, researchers put forward a variety of technical means, of which image encryption is an effective scheme. Image encryption, also known as image scrambling, is to convert a meaningful image into a chaotic image. Because the attacker cannot obtain meaningful information from the chaotic image, the security of the image information can be ensured. Taking random block strategy and chaos technology as the main starting point, this paper studies the new image encryption algorithm, designs three effective encryption algorithms, and obtains meaningful research results. Firstly, this paper reviews the development of image encryption, and then puts forward the joint exchange technology and random block fast image encryption algorithm, the image encryption algorithm based on block scrambling and chaotic mapping, and the multi-image encryption algorithm based on chaos. The specific results are as follows. 1. In this paper, a joint exchange technique and a fast image encryption algorithm based on random block are proposed. Firstly, the image is divided into four overlapping image blocks by random block technique, and then the encryption order of the image blocks is determined by the key. Finally, each image block is encrypted by pixel exchange technique, and the calculated results are written back to the image. Theoretical analysis and experimental results show that the proposed algorithm can encrypt images of any size effectively and has good security and robustness. Compared with the classical Arnold transform, the algorithm runs faster, safer and more widely used. 2. An image encryption algorithm based on image block scrambling and chaotic mapping is proposed. Firstly, the input image is randomly segmented into overlapping image blocks, and the initial image encryption is achieved by randomly scrambling the position of the image blocks. Then chaotic mapping and Arnold transform are used to generate a series of secure secret matrices. Finally the secret matrix and image blocks are randomly selected for XOR operation to achieve the final encryption purpose. The experimental results show that the proposed algorithm has the advantages of fast running speed, high security and better performance than the three literature algorithms. 3. In order to solve the problem of multi-image encryption, a multi-image encryption algorithm based on chaotic mapping is established, and the security technology of completing three images encryption at one time is studied. The algorithm regards three gray-scale images of the same size as three color components of a color image. Firstly, chaos technology is used to generate secure data sequences, then XOR calculation is carried out with gray-scale images to complete the initial encryption of a single image. Then the three initial encrypted images are spliced together into a large image, and the pixel positions in the large image are scrambled by the exchange technique, so that the pixels of the three gray-scale images are randomly distributed into the three components of the color image. Finally, three encrypted images can be combined into color images to achieve the purpose of encryption. The experimental results show that the algorithm can convert three gray-scale images of the same size into a secure color secret image. The size of the encrypted image file is smaller than the total capacity of the encrypted image file, and the performance of the algorithm is superior to the traditional Arnold transform method.
【學(xué)位授予單位】：廣西師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TP309.7;O415.5

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