Visually meaningful encryption for color images by using Qi hyper-chaotic system and singular value decomposition in YCbCr color space

In traditional image encryption algorithms, the plain-text image is encrypted into a noise-like image, which exhibits an existence of the encryption to an attacker. To solve the problem, the concept of visually meaningful image encryption (VMIE) is introduced, which can avoid human eyes' detection and improve the security of encryption. In this paper, we propose an improved VMIE scheme for color images. In the present scheme, the original image in RGB color space is transformed into YCbCr color space. Discrete wavelet transform (DWT) and discrete cosine transform (DCT) are used in Cb and Cr regions. Singular value decomposition (SVD) is performed on each DCT block and the singular value is embedded into the cover image. Qi hyper-chaotic mapping is used in the pre-encryption to enhance the security. Experimental results show that the proposed scheme has better security and performance than existing VMIE schemes and can also effectively resist common attacks.