Ciphertext-only attack on optical scanning cryptography

Abstract The optical scanning cryptography (OSC) is one of the most utilized optical encryption systems. Our research is inspired from the observation that there is a linear system property within the ciphertext expression equation of OSC. Given the linear system property, it is feasible to recover the plaintext with cipher-only attack (COA). Our proposed COA method converts the problem of COA into a phase retrieval problem with a single intensity measurement. With the frequency domain constraint and the object domain support obtained from the ciphertext of OSC, the hybrid input-output (HIO) algorithm can be used to recover plaintext. Simulation results demonstrate the feasibility and robustness of the attack. This shows for the first time that the OSC scheme is vulnerable to COA attack.