A ( k , n ) Threshold Partial Reversible AMBTC-based Visual Cryptography Using One Reference Image
A (k ، n) رمزنگاری تصویری مبتنی بر AMBTC قابل برگشت جزئی با استفاده از یک تصویر مرجع-2019
Recently, Yang et al. introduced a ðk; nÞ approach called Reversible Absolute moment block truncation coding Visual Cryptography Scheme (RAVCS) (Yang et al., 2017) to conceal a secret image into n AMBTC shares. However, a large number of reference images is used in their method. To reduce the number of reference images, a ðk; nÞ PRAVCS using one AMBTC reference image is introduced. In encoding phase, a binary secret image is shared into n AMBTC shadow images according to the base matrices generated by two proposed constructions. In decoding phase, the secret image is recovered by stacking sufficient bitmaps, and the AMBTC reference image is partially recovered as well. When n AMBTC shares are used, losslessly reconstruction for the reference image is obtained. Theoretical analysis and experiments by the proposed method are demonstrated to show the effectiveness. Moreover, Construction 1 has larger contrast, while Construction 2 achieves higher reversibility for more thresholds.
Keywords: Visual cryptography | Block truncation coding | Partial reversible | Meaningful share | Contrast | Reference image
Efficient constructions for progressive visual cryptography with meaningful shares
سازه های کارآمد برای رمزنگاری بصری مترقی با سهام معنی دار-2019
In a progressive visual cryptography scheme (PVCS), the clarity of recovered images can be enhanced by increasing the number of stacking shares. Noise-like shares are hard to identify, therefore, user-friendly progressive visual cryptography schemes (FPVCSs) generate meaningful shares. This paper proposes two encryption approaches to construct FPVCSs. One is a general OR-based FPVCS called (2, n )-FPVCS, and the other is an XOR-based FPVCS called (2, n )-XFPVCS. The common issues of the two models include: (1) systematic approaches, (2) avoiding the pixel-expansion, (3) providing adjustable visual quality of meaningful shares, and (4) eliminating residual traces of cover images. Moreover, the paper theoretically analyzes and carries out experiments to verify the visual qualities of the proposed two models. The experiment results indicate that the proposed approaches can accomplish these objectives simultaneously. In addition, (2, n )-FPVCS can adjust the threshold of trace-elimination by setting a parameter, which improves the flexibility of the proposed approach. As well as (2, n )-XFPVCS obtains a fully decrypted final recovered image.
Keywords: Visual cryptography | Visual secret sharing scheme | User-friendly progressive visual | cryptography