Abstract
This paper investigates and presents a block-based opto-color cipher using double random phase encoding (DRPE) with different block sizes. The color plainimage is divided into equal-sized blocks and then converted to an optical signal by an optical emitter. The obtained optical signal is encrypted by employing the DRPE technique, which applies two types of phase modulation, time, and Fourier domains. Finally, the optical color cipherimage is, upon detection, converted to digital format by a charge-coupled device digital camera. Experiments and security analysis show that the proposed block-based optical color image cipher using DRPE with increased block size is secure, effective, and including a good immunity to channel noise.