Double random phase encoding schemes with perfect forward secrecy for robust image cryptography

Digital cryptosystems can provide perfect forward secrecy (PFS) for key exchange protocols based on the Diffie–Hellman (DH) scheme. However, key exchange algorithms are optimally designed only to encode small datasets, such as text and voice sets, which makes rapidly processing large-scale datasets difficult. In this paper, we propose new schemes that can efficiently and securely provide PFS in double random phase encoding (DRPE) schemes for robust image cryptography. We demonstrate that the proposed complex sinusoidal waveform versions of the DH algorithm with fusion of a random phase mask (RPM) and ephemeral secret exponents can guarantee PFS. Different experimental results reveal that the proposed schemes can enhance the security of DRPE-based image cryptosystems using a one-time RPM and PFS. We also propose a ring-type PFS scheme in which an unlimited number of users can securely share a temporary session key, which is an extension of PFS for only two users. We provide formal proof for the schemes and prove feasibility through numerical simulations.