Sahoo Sujit Kumar, Tang Dongliang, Dang Cuong
Centre for OptoElectronics and Biophotonics (OPTIMUS), School of Electrical and Electronic Engineering, The Photonics Institute (TPI), Nanyang Technological University Singapore, 50 Nanyang Avenue, Singapore, 639798, Singapore.
Department of Statistics and Applied Probability, National University of Singapore, Singapore, 117546, Singapore.
Sci Rep. 2017 Dec 20;7(1):17895. doi: 10.1038/s41598-017-17916-8.
A position-multiplexing technique with ultra-broadband illumination is proposed to enhance the information security of an incoherent optical cryptosystem. This simplified optical encryption system only contains one diffuser acting as the random phase mask (RPM). Incoherent light coming from a plaintext passes through this nature RPM and generates the corresponding ciphertext on a camera. The proposed system effectively reduces problems of critical alignment sensitivity and coherent noise that are found in the coherent illumination. Here, the use of ultra-broadband illumination has the advantage of reducing the speckle contrast that makes the ciphertext more complex. Reduction of the ciphertext size further increases the strength of the ciphering. Using the spatial decorrelation of the speckle pattern we have demonstrated a position multiplexed based cryptosystem, where the ciphertext is the superposition of uniquely encrypted texts from various spatial positions. These unique spatial keys are utilized to decrypt the plaintext located at different spatial positions, and a complete decrypted text can be concatenated with high fidelity. Benefiting from position-multiplexing, the information of interest is scrambled together by a truly random method in a smaller ciphertext. A high performance security for an optical cryptosystem has been achieved in a simple setup with a ground glass diffuser as a nature RPM, the broadband incoherent illumination and small position-multiplexed ciphertext.
提出了一种具有超宽带照明的位置复用技术，以增强非相干光学密码系统的信息安全性。这种简化的光学加密系统仅包含一个用作随机相位掩模（RPM）的漫射器。来自明文的非相干光穿过这个天然的RPM，并在相机上生成相应的密文。所提出的系统有效减少了相干照明中存在的临界对准灵敏度和相干噪声问题。在这里，使用超宽带照明具有降低散斑对比度的优点，这使得密文更加复杂。减小密文大小进一步增强了加密强度。利用散斑图案的空间去相关性，我们展示了一种基于位置复用的密码系统，其中密文是来自不同空间位置的唯一加密文本的叠加。这些唯一的空间密钥用于解密位于不同空间位置的明文，并且可以高保真地拼接出完整的解密文本。受益于位置复用，感兴趣的信息通过一种真正随机的方法在更小的密文中被打乱。通过使用毛玻璃漫射器作为天然RPM、宽带非相干照明和小尺寸位置复用密文的简单设置，实现了光学密码系统的高性能安全性。
