Security-enhanced optical cryptosystem using nonergodic scrambling phase mask.

Abstract

Cryptanalysis revealed a security flaw in the double random phase encoding (DRPE) system, and the original image was recovered via a ciphertext-only attack. In this paper, a nonergodic scrambling phase mask (NESPM) is designed, and a security-enhanced cryptosystem is established by replacing the bonded random phase mask (RPM) in the DRPE system with the designed NESPM. The original image in the security-enhanced cryptosystem is optically scrambled at "macropixel" level by the bonded NESPM, instead of being diffused by the RPM, as in the DRPE system. Due to such a scrambling operation, the ergodic property of the Fourier-plane speckle pattern in the designed cryptosystem is removed, and the original image cannot be recovered via the attack. Experimental results demonstrate that the designed cryptosystem is resistant to the attack. Security enhancement is achieved.