Scheme
Thevisualcryptographicschemeisactuallyasecretsharingscheme.Evenanattackerwithinfinitecomputingpowercan’thavelessthanonesecretsecret.Getanyinformationaboutthesecretimagewhensettingthevalue.
DevelopmentHistory
ShamirIandBlakelyrespectivelyproposedtheconceptofsecretsharingin1979.Themainideaistoshareasecretbetweennparticipants,k(orkMorethanone)participantscanrecoverthesecret,butlessthankparticipantscannotrecoverthesecret,sothesecretsharingisalsocalled(k,n)thresholdscheme.
In1994,NaorandShamirproposedthatvisualcryptographyisasecretsharingmethodthatreliesonhumaneyesfordecryption.Itisasecretsharingmethodthatreliesonhumaneyesfordecryption.AsecretimageisencryptedintonSharedimages,nsharedimagesarekeptbynindividualsseparately,whendecrypting,onlyk′(k′≥k)individualsneedtosuperimposetheirrespectivesharedimages,andthesecretimagewillbepresented,andlessthankindividualscannotobtainthesecretimage.Abitofinformation.Comparedwiththeprevioustechnology,thedifferenceofthevisualpasswordisthatthesecretandtheciphertextheldbythemembersarenotastringofvaluesbutimages,andnoadditionalequipmentandcomputingaidsareneededtorestorethesecrets,directlybythehumanvisualsystem.Todecrypt,thedecryptordoesnotneedtohavecryptography-relatedknowledgetodecrypt,whichgreatlyreducesthecostanduserthreshold.Nowadays,manyextendedformsofvisualencryptiontechnologyhavebeenproposed,suchasS-Extendedvisualcipher,visualcipherwithgeneralaccessstructure,non-extendedpixeltype,superimpositiontechnique,deceptionpreventiontype,etc.