改进的引力模型耦合明文像素相关交叉机制的图像加密算法

目的解决当前图像加密技术严重依赖混沌系统,使其通用性较差,难以直接加密非方形图像,且因混沌系统的周期性,算法的安全性不足的问题。方法提出了改进的引力模型耦合明文像素相关交叉算子的图像加密算法。首先,利用多个一维混沌映射,定义联合混沌变换模型,输出密钥流;随后,基于明文像素位置,设计像素相关交叉机制,联合密钥流,对明文进行高效置乱;构造质量动态变化函数,用其替代传统引力模型中的恒定粒子质量,增强算法的敏感性,并用改进的引力模型对置乱图像完成扩散,彻底改变像素值;最后,构建密文增强模型,对输出密文进行二次扩散,扩大密文的NPCR(Number of pixel change rate)与UACI(Unified average changed intensity)值。结果实验结果表明:与当前图像加密机制相比,所提加密算法不但可以扩散方形图像,而且能够对非方形目标直接加密,具有更高的通用性与安全性,以及更强的抗差分攻击能力。结论所提出的算法能够加密非方形尺寸的图像,具有较强的通用性与安全性。

Image Encryption Algorithm Based on Improved Gravity Model Coupled with Plain Pixel Correlation Crossing Mechanism

In order to solve the problems such as bad versatility of image encryption and difficulty in directly encrypting non-square images which were caused by severe dependence on chaotic system, and also insufficient algorithm security because of the periodicity of the chaotic system, an improved encryption algorithm was put forward based on improved gravity model coupled with plain pixel correlation crossing mechanism. Firstly, this algorithm defined the combined chaotic transformation model by multiple 1D chaotic maps and output the key stream; and then, it designed pixel correlation crossing operator based on the location of plain pixels, and efficiently scrambled the plain image by combining the key stream; built dynamic variation function of mass to substitute the constant particle mass in the traditional gravity model and increase the sensitivity of the algorithm; and then diffused the permutation image with the improved gravity model to completely change the pixel value; finally it built an enhanced model to have secondary diffusion for the output cryptograph and increase its NPCR (number of pixels change rate) and UACI (unified averaged changed intensity). Compared with the current image encryption algorithm, the proposal could not only diffuse square images but also directly encrypt non-square objects, and it had higher versatility and security and stronger ability to resist differential attacks. The algorithm proposed can encrypt non-square images and have better versatility and security.