User-friendly visual cryptography with complementary cover images

User-friendly visual cryptography schemes (denoted as (n, n) - FVCSs) generate meaningful shares to cope the management problem of conventional visual cryptography. However, several issues still remain in this research field, including: pixel expansion, residual traces of cover images, low visual quality of meaningful shares and recovered images, lack of systematic encryption methods, and others. To solve the abovementioned problems, this paper proposes a novel (n, n) - FVCS for sharing binary secret images. We extend the probabilistic (n, n) - VCS and embed complementary cover images in shares to construct the (n, n) - FVCS. The proposed approach provides an adjustable contrast for meaningful shares to satisfy dealers' requirements. Moreover, the experimental results indicate that the proposed (n, n) - FVCS significantly outperforms the previous methods in terms of the quality of the recovered images and meaningful shares.