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Conventional visual secret sharing schemes generate noise-like random pixels on shares to hide secret images. It suffers a management problem, because of which dealers cannot visually identify each share. This problem is solved by the extended visual cryptography scheme (EVCS), which adds a meaningful cover image in each share. However, the previous(More)
Conventional visual secret sharing (VSS) schemes hide secret images in shares that are either printed on transparencies or are encoded and stored in a digital form. The shares can appear as noise-like pixels or as meaningful images; but it will arouse suspicion and increase interception risk during transmission of the shares. Hence, VSS schemes suffer from(More)
Conventional visual cryptography (VC) suffers from a pixel-expansion problem, or an uncontrollable display quality problem for recovered images, and lacks a general approach to construct visual secret sharing schemes for general access structures. We propose a general and systematic approach to address these issues without sophisticated codebook design.(More)
Reducing the pixel expansion and improving the display quality of recovered images are still major issues in visual cryptography schemes (VCSs), particularly for large <i>k</i> and <i>n</i>. Moreover, the development of a systematic and practical approach for threshold VCSs is a challenge. In this paper, a pixel-expansion-free threshold VCSs approach based(More)
Visual cryptography schemes (VCSs) generate random and meaningless shares to share and protect secret images. Conventional VCSs suffer from a transmission risk problem because the noise-like shares will raise the suspicion of attackers and the attackers might intercept the transmission. Previous research has involved in hiding shared content in halftone(More)
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(More)
In progressive visual cryptography schemes, visual qualities of recovered images appear multi-level upgrade when the number of the stacked shares increases. For identifying noise-like shares that belong to different secret images, providing meaningful shares is necessary. Based on the XOR-ed operation, this study proposes a novel encryption approach to(More)
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