This study presents a steganographic optical image encryption system based on reversible data hiding and double random phase encoding (DRPE) techniques. Conventional optical image encryption systems can securely transmit valuable images using an encryption method for possible application in optical transmission systems. The steganographic optical image encryption system based on the DRPE technique has been investigated to hide secret data in encrypted images. However, the DRPE techniques vulnerable to attacks and many of the data hiding methods in the DRPE system can distort the decrypted images. The proposed system, based on reversible data hiding, uses a JBIG2 compression scheme to achieve lossless decrypted image quality and perform a prior encryption process. Thus, the DRPE technique enables a more secured optical encryption process. The proposed method extracts and compresses the bit planes of the original image using the lossless JBIG2 technique. The secret data are embedded in the remaining storage space. The RSA algorithm can cipher the compressed binary bits and secret data for advanced security. Experimental results show that the proposed system achieves a high data embedding capacity and lossless reconstruction of the original images.
This paper presents a public-key-based optical image cryptosystem with adaptive steganography for practical secure communications. The optical image cryptosystem employs a hybrid architecture for ciphering and deciphering in which double random-phase encoding and asymmetric encryption algorithms are utilized for images and session keys, respectively. The session key is safely protected and transmitted by using an asymmetric encryption algorithm and an adaptive steganographic scheme, respectively. To perform the adaptive steganographic scheme, a sorting technique is used to find the suitable embedding position in the embedding domain, a least-significant-bit truncation algorithm is presented to find the invariant hiding order, and a quantization-based data-embedding algorithm is utilized to hide message bits. Experimental results show that the proposed scheme is superior to that of a previous one due to Lin et al., no matter what embedding domain, quantization level, and message size are used. Especially, compared with the latter scheme a large improvement (22.56 dB) of image quality is achieved by using the proposed adaptive steganographic scheme.