基于螺旋相位变换和广义Fibonacci混沌的光学图像加密

为了解决光学加密技术中混沌序列分布不均匀，抗选择明文攻击能力弱以及菲涅尔域双随机相位编码系统对第1个衍射距离不敏感等问题，该文基于螺旋相位变换和新型广义Fibonacci混沌系统，提出一种光学图像加密算法。在菲涅尔域的双随机相位编码中对明文图像进行相位编码和螺旋相位变换，克服系统对第1块随机模板和衍射距离不敏感的缺陷，提高光学密钥敏感性。添加安全图像与明文进行加权干涉，进一步提高光学密钥敏感性和密钥维度。构造可产生均匀混沌序列的广义Fibonacci混沌系统生成随机模板，解决密钥体积过大分发传递困难问题，克服Logistic混沌分布不均匀的缺点，提高密钥传输效率及密钥敏感性。同时用明文哈希值SHA-256生成混沌初值和螺旋相位变换参数，使得密钥流随明文自适应变化，达到“一次一密”的效果，提高算法抵抗选择明文攻击能力和明文敏感性，雪崩效应更强。实验对比表明该算法明文及密钥敏感性高，密钥空间大，鲁棒性好，能有效抵御各种攻击，是一种高安全性的光学图像加密方法。

Optical Image Encryption Based on Spiral Phase Transform and Generalized Fibonacci Chaos

In this paper, an optical image encryption algorithm based on spiral phase transform and new generalized fibonacci chaotic system is proposed to solve the problems of the Fresnel domain double random phase coding system is insensitive to the first diffraction distance, uneven distribution of chaotic sequences and weak resistance to choice plaintext attack. The plaintext image is encoded as phase information and spiral phase transformed to overcame the insensitivity of the first random phase template and diffraction distance of the Fresnel diffraction transform-double random phase encoding system. The sensitivity of the optical keys is improved. The weighted interference between secure image and plaintext image is added to further increase the sensitivity of the optical keys and dimension of key . A generalized Fibonacci chaotic system, which could generate uniform sequences, is constructed to generate phase templates to overcame uneven distribution of logistic chaos and improve the efficiency of key transmission and the sensitivity of the keys. The chaotic initial value and parameters of spiral phase transform are related to SHA-256. It makes the keys change with the plaintext and achieved the effect of “one encryption at a time”, and enhanced the sensitivity of the plaintext and the ability of the resistance to choice plaintext attack and avalanche effect.Experimental comparison shows that this method can effectively increase the plaintext sensitivity and key sensitivity. This method’ robustness and the key space are sufficiently secure. It is a high security optical image encryption method.