Optical encryption using uncorrelated characteristics of dynamic scattering media and spatially random sampling of a plaintext.

Scattering media are generally regarded as an obstacle in optical imaging. However, the scattering of a diffuser can be exactly taken as an advantage to act as random phase masks in the field of optical encryption to enhance information security. Here, we propose and demonstrate a dynamic diffuser based optical encryption method, which increases the ciphering strength by exploiting the uncorrelated characteristics of the dynamic diffuser as well as randomly sampling the plaintext multiple times. The light emitted from a randomly sampled plaintext passing through the dynamic diffuser generates noise-like speckles, and then SNR of the recorded speckles is further reduced for obtaining the ciphertexts, which makes COA using PRA almost impossible. The specific uncorrelated characteristics of the dynamic diffuser make the ciphertexts and the PSF keys of the optical encryption unique. Therefore, only authorized users who mastered the keys can decrypt the plaintext. The proposed method is very simple and flexible since it can also achieve the encryption offline by performing convolutions on partial-plaintexts with pre-recorded uncorrelated PSFs to generate speckle patterns and then reducing their SNR to obtain the ciphertexts. This type of encryption technique has a promising prospect in applications involving images and/or videos information encryption owing to its simplicity and flexibility.