结合四维超混沌系统和位分解的图像加密算法研究

该文针对数字图像传输的安全性问题，基于四维超混沌系统，提出一种新的位级图像加密算法.首先对四维超混沌系统生成的混沌序列进行分类处理，得到具有良好性能的伪随机二进制序列。接着对明文图像进行位分解，得到8个位面，分别对高3位和低5位对应的位面进行行列循环移位置乱，并将置乱后的位面嵌入由伪随机二进制序列得到的4个载体矩阵，对4个载体矩阵执行按位异或运算后得到初步密文。最后，再利用伪随机二进制序列产生的扩散矩阵，对初步密文像素执行线性双向扩散，得到最终的加密图像。数值实验和结果分析显示，算法密钥空间大，可以有效抵御暴力穷举、统计分析和差分分析等恶意攻击，具有较高的安全性。同时，算法也具有较好的执行效率。

Image Encryption Algorithm Research by Combining Four Dimensional Hyper-Chaotic System and Bit Decomposition

For the transmission security of digital image, a novel bit-level image encryption algorithm is proposed by using a four dimensional (4D) hyper-chaotic system. Firstly, a pseudo-random binary sequence with good performance is obtained by classifying the chaotic sequences generated from the hyper-chaotic system. Then, the plain-image is decomposed into 8 bit-planes, the higher 3 and lower 5 bit-planes are shuffled separately by using circular shift of their rows and columns, and the resulting bit-planes are further embedded into four carrier matrices generated from the pseudo-random sequences. The preliminary cipher-image is obtained by performing exclusive-OR operation on the four carrier matrices. Finally, a linear pixel diffusion in two directions is performed on the preliminary cipher-image by using the diffusion matrix also generated from the binary sequence, after which the final encrypted image is obtained. Experiments and result analysis demonstrate that the algorithm has a high security with large key space and can resist common attacks including brute-force, statistical and differential analysis, etc. Furthermore, it also has a good efficiency.