Secure selective recovery protocol for multiple optically encrypted data

Abstract

In this work we present a secure selective recovery protocol for multiple optically encrypted data based on sampling with orthogonal random binary masks. In this protocol, every single object is encrypted using a single arm free-space cryptosystem, filtered and multiplied by an orthogonal random binary mask, then all the encrypted, filtered and sampled objects are multiplexed. Under this protocol, an authorized user can access a single object from the multiplexed data using both the encryption key and the corresponding orthogonal random binary mask. Without knowledge of the orthogonal binary masks used in the process, neither authorized users nor attackers can recognize the amount of multiplexed data. As a demonstration of the usefulness of our proposal, we implement an optically encrypted keyboard in which each letter is recovered individually without crosstalk. We can securely deliver messages of arbitrary length by sending the encrypted keyboard, the encryption key, and the corresponding set of binary masks. We perform tests showing the resistance of the processed data to occlusion and random noise. Additionally, we discuss the potential resistance of our proposal to Dirac delta and chosen plaintext attacks. Finally, a holographic projection setup is implemented to perform a selective experimental reconstruction of the original objects. The experimental results demonstrate the viability and validity of our proposal.