Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronics Engineering, Shenzhen University, Shenzhen 518060, China.
Sci Rep. 2017 Jan 31;7:41789. doi: 10.1038/srep41789.
Security analysis is important and necessary for a new cryptosystem. In this paper, we evaluate the security risk of the optical cryptosystem with spatially incoherent illumination from the view of imaging through scattering medium and then demonstrate that it is vulnerable to ciphertext-only attack. The proposed ciphertext-only attack method relies on the optical memory effect for speckle correlations, which reveals a fact that the ciphertext's autocorrelation is essentially identical to the plaintext's own autocorrelation. Furthermore, by employing of an improved dynamic hybrid input-output phase-retrieval algorithm, we show that a plaintext image can be directly reconstructed from the autocorrelation of its corresponding ciphertext without any prior knowledge about the plaintext or the phase keys. Meanwhile, the theory analysis and experiment results will also be provided to verify the validity and feasibility of our proposed ciphertext-only attack method. To the best of our knowledge, this is the first time to report optical cryptanalysis from the point of view of imaging through scattering medium and we believe this contribution will open up an avenue to deepen the investigation of optical cryptosystems.
安全性分析对于新的密码系统是重要且必要的。在本文中，我们从通过散射介质成像的角度评估了非相干照明的光学密码系统的安全风险，然后证明它容易受到仅密文攻击。所提出的仅密文攻击方法依赖于散斑相关性的光学记忆效应，这揭示了一个事实，即密文的自相关实质上与明文的自相关相同。此外，通过采用改进的动态混合输入-输出相位恢复算法，我们表明可以从相应密文的自相关直接重建明文图像，而无需关于明文或相位密钥的任何先验知识。同时，还将提供理论分析和实验结果来验证我们提出的仅密文攻击方法的有效性和可行性。据我们所知，这是第一次从通过散射介质成像的角度报告光学密码分析，我们相信这一贡献将开辟深化光学密码系统研究的途径。
