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Research On Threshold Multi-secret Visual Cryptography Schemes

Posted on:2014-08-13Degree:MasterType:Thesis
Country:ChinaCandidate:G ShenFull Text:PDF
GTID:2268330401976795Subject:Military Equipment
Abstract/Summary:PDF Full Text Request
As an important part of the multi-secret visual cryptography, threshold multi-secret visual cryptography draws researchers’ research interests due to its special access structure. This thesis expounds the multi-secret visual cryptography research background and current situation, and points out the existing problems in single threshold schemes and multi-threshold schemes. It focuses on the research of the perfect recovery of threshold multi-secret visual cryptography, and then constructs a general threshold multi-secret visual cryptography scheme.Firstly, with the idea that discarding some information of the secret image to exchange for no pixel expansion, this thesis designs a single threshold multi-secret visual cryptography scheme based on random numbers. In this scheme, the shares are generated with random numbers and the secret images are recovered by the XOR operation, and also a process of multi-secret sharing and recovering is designed based on the pixel sharing algorithm and cylinder shares rotation operation. It not only shares t secret images among multiple participants with no pixel expansion, but also increases the relative difference to1/t.Secondly, on condition of not increasing the calculation complexity of the recovery operation, this thesis gives a proof that the definition of contrast based on the Hamming weight is the sufficient condition of the perfect recovery of threshold multi-secret visual cryptography schemes. Meanwhile, with the design idea that increasing the pixel expansion to exchange for secret images’ perfect recovery, this thesis designs a multi-secret sharing and recovering algorithm based on the arithmetic sequence rotating rules under (n, n) threshold structure. The proposed scheme not only shares many secret images between multiple participants, but also realizes the secret images’perfect recovery.Furthermore, on the basis of the above design idea, this thesis designs a (k, n) multi-secret visual cryptography scheme. This scheme designs an irregular rotation algorithm based on the threshold structure and the secret number. On condition of perfect recovery, it solves the multi-secret sharing problems under single threshold structure, and extends the access structure.Finally, according to the sufficient condition of perfect recovery, this thesis gives a general definition of threshold multi-secret visual cryptography scheme, which can adapt to the various corresponding relationship between threshold value and secret number. Furthermore, it takes the single threshold multi-secret visual cryptography scheme with upper and lower thresholds as a unit, and gives a multi-threshold scheme, which accords with the above definition, by designing the rotation rule fusion algorithm and the region merging algorithm. It realizes the general correspondence between the threshold value and the secret number on the basis of perfect recovery. The contents of this thesis provide an effective way for multiple secret images sharing in visual cryptography.
Keywords/Search Tags:Visual Cryptography, Multi-secret, Single Threshold, Multi-threshold, No PixelExpansion, Perfect Recovery
PDF Full Text Request
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