基于L-L级联混沌与矢量分解的无损压缩光学图像加密

为克服双随机相位编码的光学图像加密中,密钥、密文体积大、抗选择明密文能力弱的问题,提出了一种Logistic-Logistic级联混沌与矢量分解的无损压缩光学图像加密方法 .先隔空取样置乱将明文分成两块,再用干涉合成一块,最后放入双随机相位编码系统得到密文.置乱能够克服干涉后看到明文信息的缺点,增加了加密系统的安全性.干涉使得密文体积变为原来的一半,便于密文传输.单位等模矢量分解的解密方式避免了现有压缩方式存在的解密图像分辨率降低的问题.Logistic-Logistic级联混沌极大缩小了双随机相位编码的密钥体积,同时还解决了Logistic序列分布不均匀问题,提高了序列随机性,保留了Logistic混沌的快速性.将明文的HASH值SHA256与密钥进行强关联,使整个系统达到一图一密的加密效果,提高了明密文间的雪崩效应,增强了算法抗选择明密文攻击的能力.

Lossless Compression Optical Image Encryption Based on L-L Cascade Chaos and Vector Decomposition

In order to avoid the characters of current double-random phase-encoded optical image encryption,whose key and ciphertext are large in size,and has weak ability to resist the attack of selecting plaintext and ciphertext,a lossless compression optical image encryption method was proposed based on Logistic-Logistic cascade chaos and vector decomposition. Firstly,the plaintext is divided into two images by space sampling and scrambling. Then the images are synthesized together by the interference. At last,the ciphertext can be gotten by putting the image into a double random phase encoding system. The scrambling improves the security of the encryption system,because it can avoid plaintext information to be seen after interference. The interference reduces the volume of the ciphertext to about the half in size,which is convenient for ciphertext transmission. The decryption method based on unit-mode vector decomposition could avoid the problem of low resolution of the decrypted image caused by the existing compression method. Logistic-Logistic cascade chaos can reduce the volume of double random phase encoding,improve the randomness of the sequence and keep the fastness of the Logistic chaos. It can also solve the problems of uneven distribution of the Logistic sequence. The HASH value SHA256 of plaintext is associated with the secret key strongly,which makes the whole system achieve the encryption effect of one image with one key. This also improves the avalanche effect between plaintext and ciphertext,and enhances the capability of resisting the attack of selecting plaintext and selecting ciphertext.