基于增强型视觉密码的光学信息隐藏系统

Enhanced-visual-cryptography-based optical information hiding system

提出了一种基于增强型视觉密码的光学信息隐藏系统.该系统可将秘密图像分解为多幅有实际意义的分享图像,然后将这些分享图像隐藏在相位密钥中,相位密钥可以制成衍射光学元件,以实体的形式保存和传输,扩展了视觉密码的应用范围.在提取过程中,只需要使用激光照射衍射光学元件,再现分享图像,然后只需要将一定数量的分享图像进行非相干叠加即可提取秘密图像,不需要额外掌握光学和密码学的知识,其简单性让任何人都可以使用.仿真实验和光学实验结果表明,该系统可应用于实际,并且具有良好的安全性.

Recent years,with the rapid development of information technology,the information security has received more and more attention.A variety of encryption methods to protect the information have been reported.Visual cryptography is one of the encryption methods,which has highly security because of its threshold feature.And the cryptographic information can be explained by a naked eye in the decryption process.In the application of visual cryptography,however,each shared image is limited to transparency films and overlapping on computer.In our previous work,we proposed the scheme of invisible visual cryptography and developed the visual-cryptography-based optical hiding system(VCOH),which transformed the conventional visual cryptography shares into diffraction optical elements(DOEs).It not only increases the application range of visual cryptography,but also enhances security.In this paper,we propose an optical information hiding system based on the extended visual cryptography,which inherits the concept of invisible visual cryptography.In contrast to our previous work,the method proposed in this work can hide a meaningful image instead of text messages.Meanwhile,the capacity and imperceptibility of the method are greatly increased.The hiding process of the system contains two steps.Firstly,the secret image is converted into meaningful shares through the extended visual cryptography algorithm.Secondly,the meaningful shares are able to hide in phase-keys through an iterative phase retrieval algorithm,such as Gerchberg-Saxton algorithm and Yang-Gu iterative algorithm.Then the phase-keys can be made into diffraction optical elements(DOEs)to store and transport in a physical way.In the decryption process,DOEs are illuminated with the laser beam to reconstruct the meaningful shares.The secret image can be explained by the direct overlapping of the reconstructed shares without any optical or cryptographic knowledge.The simulation and optical experimental results show that the proposed method has good performance of security and validate the feasibility of the proposed method.Besides,in this paper the robustness and security issues are also analyzed.This system has a high security because of its indistinguishability under adaptive chosen ciphertext attack(IND-CCA2)security.Additionally,this system is relatively less robust than the VCOH because it shares meaningful images with highly complex and detailed structures.