为了实现对两个明文进行同步安全加密,提出了联合离散多参数分数阶角变换与低维映射的 双图像加密算法。基于离散余弦变换(DCT)与Zigzag扫描建立了复合系数矩阵模型,通过反离散余弦 变换(IDCT)将两个明文融合成一幅图像;通过耦合Logistic映射,利用明文像素均值与外部密钥计算 其初始条件值,并迭代该耦合映射,输出2个随机序列;分别对这2个随机序列进行排序,设计位置数 组扰乱机制对复合明文进行置乱;将置乱密文分解为2个新分量, 利用Logistic映射与初始明文分别生成混沌随机与调制相位掩码,将2个新分量融合成临时密文;基于 离散分数角变换构建了新的2D多参数分数阶角变换,设计加密模型并完成图像加密。结果表明,与已有 双图像加密机制相比所提算法的保密性更佳,有更好的抗明文攻击特性。

In order to realize the synchronous secure encryption of two plains, a double image encryption algorithm based on the combination of discrete multi-parameters fractional angle transform and low dimension mapping is proposed. The composite coefficient matrix model is constructed based on discrete cosine transform (DCT) and Zigzag scanning, and the two plains are merged into an image by using inverse discrete cosine transform (IDCT). The initial condition values are calculated by using mean value of the plain pixel and external key with the coupled Logistic mapping, and two random sequences are outputted by iterating this coupling map. The position array disrupt mechanism is constructed by sorting two random sequences for scrambling compound plain. The scrambling cipher is decomposed into two new components, and the two new components are fused into temporary cipher by combining the chaotic random phase mask generated by logistic map with modulated phase mask. A new 2D multi-parameter fractional angle transform is constructedbased on discrete fractional angle transform. The encryption model is designed and image encryption is completed. Results show that the proposed algorithm is more secure than the existing dual image encryption schemes, and has better anti-plaintext attack characteristics.