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A novel quantum steganography scheme is investigated based on efficient embedding algorithm of modified exploiting modification direction in this paper, which embeds two 2 n × 2 n binary images (secret information) into a 2 n × 2 n color image (carrier image). To improve the security of the secret information and enhance the robustness of the proposed scheme, a 2 n × 2 n binary image (secret key) is generated according to the exclusive or operation of two secret images. The secret key acts as the control key of choosing two channels from the carrier image's three channels of R, G and B (i.e., R, G or R, B channels chose as the pixel-group) to hide the secret information. In addition, the effective quantum circuits for investigated quantum steganography scheme are illustrated to better understanding the procedure of embedding algorithm. The experiment results simulated on the classical computer with MATLAB environment, and the numerical analyses demonstrate that the presented algorithm has good performance on imperceptibility and security. [ABSTRACT FROM AUTHOR]

Based on the modified flexible representation of quantum images, a novel quantum image encryption algorithm was proposed in this paper. The encryption process performs Arnold scrambling operation to disturb the quantum image information in spatial domain first. Then, quantum wavelet transforms are employed to decompose the scrambled quantum image into multiscale resolution (i.e., a sequence of subimages) in the frequency domain, which are mainly divided into two parts: the low-frequency component (i.e., the approximation) and high-frequency detail information (i.e., the horizontal details, vertical details and diagonal details in each decomposition level). Following that, Arnold scrambling operations are implemented to encrypt the wavelet coefficients within each subimage in the frequency domain once again. Finally, based on inverse quantum wavelet transforms, the encrypted wavelet coefficients can affect the pixel values of the entire reconstructed quantum images. Due to the fact that all the quantum operations are invertible, the decryption process of the encrypted image is performed in a straightforward manner by reversing all of the quantum operations within quantum image encryption process. The proposed encryption algorithm is simulated on a classical computer with MATLAB environments. Experimental results and numerical analysis indicate that the presented algorithm has a good encrypted effect and high security. [ABSTRACT FROM AUTHOR]