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《基于dct和混沌擴頻數(shù)字水印算法的研究》由會員上傳分享，免費在線閱讀，更多相關(guān)內(nèi)容在學(xué)術(shù)論文-天天文庫。
1、摘要數(shù)字圖象加密源于早期的經(jīng)典加密理論，其目的是將一幅給定的圖象按一定的變換規(guī)則在空域或頻域?qū)⑵渥儞Q為一幅雜亂無章的圖象，從而隱藏其圖象本身的真實信息。數(shù)字水印技術(shù)作為版權(quán)保護(hù)的重要手段，得到廣泛的研究和應(yīng)用。它通過在原始數(shù)據(jù)中嵌入秘密信息—水印(watermark)來證實該數(shù)據(jù)的所有權(quán)或完整性，以此來抵制對數(shù)字作品的盜版或篡改等。本論文的主要研究內(nèi)容如下:(1)從數(shù)字水印的概念、分類、基本框架、常用的水印算法、研究現(xiàn)狀及其主要應(yīng)用領(lǐng)域等方面對數(shù)字水印技術(shù)作了概括性介紹。(2)實現(xiàn)了基于混沌的DCT(DiscreteCosineTra
2、nsform)域數(shù)字圖象水印算法。為了提高水印的加密性和提取出的水印的視覺效果，我們對二值水印信號進(jìn)行了一些預(yù)處理。在DCT水印算法中，利用混沌的特性將混沌序列應(yīng)用到水印的嵌入過程中，提高水印的安全性，同時水印信號嵌入后對圖象影響較小，有利于保證水印的不可見性。(3)為了評估水印算法的性能，對嵌入水印后的圖象進(jìn)行常用的信號處理攻擊，包括有加性噪聲、抗剪切、抗Jpeg壓縮等等。關(guān)鍵詞:數(shù)字水印;離散余弦變換;混沌序列;圖象置亂;人類視覺系統(tǒng)IAbstractTheencryptionofdigitalimagewasderivedfro
3、mtheearlyclassicalencryptiontheories.Thepurposeofitwastochangeagivenimageintoanout-of-orderimageinspacedomainorinfrequencydomainbyarulesothattherealinformationoftheimageitselfwashidden.Digitalwatermarkingtechnologyasaneffectivemeansofknowledgecopyrightprotectioniswidely
4、studiedandused.Itembedssomesecretmessages----watermarksintothemediatoprotectthepropertyorintegralityoftheworkingsothatdigitalproducescanresistbeingcopied,tamperedandsoon.Inthepaper,thetechnologyandapplicationofthedigitalimagewatermarkingaredeeplyanalyzedandstudied,thema
5、inworkisasfollows:(1)Wemakearecapitulativesummarizeandanalysisforthebasicknowledgeofdigitalwatermarkingtechnologyfromitsorigin,basiccharacter,sort,commonmodel,mainapplicationfieldandsoon.(2)Inthepaper,basedondiscretecosinetransformondigitalwatermarkingarefinished.Inorde
6、rtoenhancethewatermarkingencryptionandvisioneffectoftheextractedwatermarking,firstlyatwo-valuewatermarkingsignalshouldbedealtwithbyshuffle,thetimesmaybeasapartofthekey,andthenismodulatedbychaoticsequence.Inthefirstone,watermarkingisembeddedintothechosesub-imagefromorigi
7、nalimage.WatermarkisembeddedintothelowfrequencycoefficientsofDCT,becausethelowfrequencypartoftheimagecollectsamajorityofenergyoftheoriginalimageandhasabiggishvalue.Attackerwillinevitablyaffectthequalityoftheimagewhenhedestroyswatermarks.Wecangainenoughrobustnessandimper
8、ceptibilitybythisway.Inthisway,werealizeblindextractingalgorithm.II(3)Inordertofurtherevaluateperformanceofthe
