基于多模光纤散斑的压缩感知在光学图像加密中的应用

为了安全高效地对图像信息进行传输,提出了一种新颖的基于多模光纤散斑的压缩感知结合双随机相位编码的光学图像加密方法.多模光纤产生的光斑作为压缩感知的测量矩阵,完成对图像的第一次压缩和加密,并且充当第一级密钥;再利用双随机相位编码技术进行第二次加密,实现对图像的完整加密过程,随机相位掩模板充当第二级密钥,解密过程与此相反.通过将光斑测量矩阵与用于压缩感知的常用随机测量矩阵进行对比研究后发现,使用光斑测量矩阵解密后的图像质量更好,而且相比于其他随机测量矩阵在硬件实现上的复杂性与高成本,光斑矩阵可以很容易地通过简单的光学器件来获得,且可以利用工作波长的改变来进行变换,也即第一级密钥非常容易变换.同时经研究表明,本文方法可以有效抵抗统计分析、噪声干扰和剪切等攻击,且对密钥敏感性高,具有良好的鲁棒性和安全性.因此,本文提出的这种基于光斑矩阵的压缩感知与双随机相位编码结合起来的加密方法,可以获得良好的加密效果与极大的密钥空间,并且易于在光学领域整合.

Application of compressive sensing based on multimode fiber specklegram in optical image encryption

In order to ensure the secure and effective transmission of image information,a new method of optical image encryption using the multimode fiber(MMF)specklegram based compressive sensing combined with the double random phase encoding(DRPE)is proposed in this paper.The specklegrams obtained from the facet of the multimode fiber are used as the measurement matrix of compressive sensing(CS),and the compression and the first-stage encryption of the image are completed by compressive sensing,in which the specklegram also functions as the first secret key.Then,the second-stage encryption is implemented by using the double random phase encoding technology,in which the random phase mask acts as the second secret key.All of the specklegrams used in this paper are obtained from the facet of a 5 m-long and 105-m-diameter-MMF and offset launching technique.Then the fiber specklegrams are proposed in several steps to provide the measurement matrix in CS.By performing an encryption and decryption test on a standard Lena image of 256×256 size,it is found that the decrypted image and the original image are visually consistent,and the encryption is also realized in the process of compression,which indicates the method proposed in this paper is feasible.Furthermore,the comparison studies of the performances of specklegram based measurement matrix and some classic measurement matrices show that the decrypted image quality using the specklegram matrix is better.And at the same time,comparing with the high hardware implementation complexity and high cost of other measurement matrices,specklegram based matrix can be easily realized by simple optical device,and the corresponding secret key can be easily changed by the working wavelength,which is helpful for enlarging the secret key space.It is further proved that the encryption method be able to effectively resist the statistical analysis attacks,cropping attacks and noise interference,and also have high sensitivity to the secret key,which shows good robustness and high security.Therefore,the image encryption method combined with the specklegram matrix based compression sensing with the optical DRPE can obtain good encryption effect and has a great secret key space,which may provide a good candidate scheme for the pure optical realization of image encryption.