下面是一个包含单一根元素的文档.ppt

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1、Watermarking semi-Structure data黄华军What is the semi-structure data?Semi-structures are characterized by value lying both in the structure itself and in the individual nodes.Examples:XML documents Complex Web Content Relational DBMS Data etc.Problems&ChallengesIn most media watermarking,the noise-ban

2、d is usually the main recipient;Problems:Lack of bandwidth;Trade-offsChallenges:Discovering appropriate bandwidth channels;Using them in a most efficient and resilient way;The ModelStructure watermarkingUnderstand the applicationUnderstand the essence of the cover textXMLXML(Extensible Markup Langua

3、ge)is a simple,very flexible text format derived from SGML.Originally designed to meet the challenges of large-scale electronic publishing,XML is also playing an increasingly important role in the exchange of a wide variety of data on the Web and elsewhere Mrs.Mrs.Mary Mary McGoonMcGoon 1401 Main St

4、reet 1401 Main Street AnytownAnytown 34829 34829 Tags,elements,and attributes A tag is the text between the left angle bracket()and A tag is the text between the left angle bracket().There are starting tags(such the right angle bracket().There are starting tags(such as)and ending tags(such as)as)and

5、 ending tags(such as)An element is the starting tag,the ending tag,and An element is the starting tag,the ending tag,and everything in between.In the sample above,the everything in between.In the sample above,the element contains three child elements:,element contains three child elements:,and.,and.

6、An attribute is a name-value pair inside the starting tag An attribute is a name-value pair inside the starting tag of an element.In this example,state is an attribute of of an element.In this example,state is an attribute of the element;in earlier examples,was an the element;in earlier examples,was

7、 an element element Invalid,valid,and well-formed XNL documentsInvalid documents dont follow the syntax rules Invalid documents dont follow the syntax rules defined by the XML specification.If a developer defined by the XML specification.If a developer has defined rules for what the document can has

8、 defined rules for what the document can contain in a DTD or schema,and the document contain in a DTD or schema,and the document doesnt follow those rules,that document is doesnt follow those rules,that document is invalid as well.invalid as well.Valid documents follow both the XML syntax Valid docu

9、ments follow both the XML syntax rules and the rules defined in their DTD or rules and the rules defined in their DTD or schema.schema.Well-formed documents follow the XML syntax Well-formed documents follow the XML syntax rules but dont have a DTD or schema.rules but dont have a DTD or schema.well-

10、formed XML documents1、The root element 2、Elements cant overlap 3、End tags are required4、Elements are case sensitive5、Attributes must have quoted values 下面是一个包含单一根元素的文档：Hello,World!下面是一个不包含单一根元素的文档：Hello,World!Hola,el Mundo!I really love XML.I really love XML.YadaYada yadayada yadayada.YadaYada yaday

11、ada yadayada./In HTML,and are the same;in XML,theyre not.If you try to end an element with a tag,youll get an error.Elements are case sensitive Elements are case sensitive There are two rules for attributes in XML documents:Attributes must have values Those values must be enclosed within quotation m

12、arks,can use either single or double quotes,just as long as youre consistent.Document Type Definition(DTD)A DTD defines the elements that can appear in an XML document,the order in which they can appear,how they can be nested inside each other,and other basic details of XML document structure.DTDs a

13、re part of the original XML specification and are very similar to SGML DTDs.!-!ELEMENT address(name,street,city,state,postal-code)/XML schema Schemas define elements that can appear in a document Schemas define elements that can appear in a document Schemas define attributes that can appear in a Sch

14、emas define attributes that can appear in a document document Schemas define which elements are child elements Schemas define which elements are child elements Schemas define the order of child elements Schemas define the order of child elements Schemas define the number of child elements Schemas de

15、fine the number of child elements Schemas define whether an element is empty or can Schemas define whether an element is empty or can include text include text Schemas define data types for elements and attributes Schemas define data types for elements and attributes Schemas define default and fixed

16、 values for elements Schemas define default and fixed values for elements and attributes and attributes name=state value=2/name=postal-code value=0-95(-0-94)?/Document Object Model(DOM)The Document Object Model,commonly called The Document Object Model,commonly called the DOM,defines a set of interf

17、aces to the the DOM,defines a set of interfaces to the parsed version of an XML document.The parser parsed version of an XML document.The parser reads in the entire document and builds an in-reads in the entire document and builds an in-memory tree,so your code can then use the memory tree,so your c

18、ode can then use the DOM interfaces to manipulate the tree.You can DOM interfaces to manipulate the tree.You can move through the tree to see what the original move through the tree to see what the original document contained,you can delete sections of document contained,you can delete sections of t

19、he tree,you can rearrange the tree,add new the tree,you can rearrange the tree,add new branches,and so on branches,and so on Model of information hiding using XMLTechnology of bandwidth Representation of empty elementsWhite spaces in tagsAppearing order of the elements Appearing order of the attribu

20、tesElements containing other elementChange structure of the XMLRepresentation of empty elementsWhite spaces in tagsAppearing order of the elementsAppearing order of the attributesElements containing other elementChange structure of the XMLA watermark can be embedded into a XML document by means of c

21、hanging the array of elements and attributes,changing the code of characters,or inserting some tiny spaces.This paper proposes that a XML document is considered as tree model,and a watermark can be embedded into a XML document by changing the treelike structure of the XML document.The Principle如果在XM

22、L文档中的某些特定叶子节点变成父节点的属性值，可以给这个变化定义为水印信息位1，如果没有发生变化，可以定义为水印信息位0。通过这一规则，我们可以进行嵌入和提取水印。/payment John Smith John Smith 5,000 5,000 USDUSD 4019 0122 3434 4019 0122 3434 Visa Visa 04/12/31 04/12/31 /John Smith 4019 0122 3434 Visa 04/12/31Embedded Algorithm 输入：输入：XMLXML文档，水印信息文档，水印信息 ，密钥。，密钥。输出：带有水印的输出：带有水印的

23、XMLXML文档。文档。1 1）初始化）初始化XMLXML文档，计算出叶子节点数：文档，计算出叶子节点数：。用表示第个叶子节。用表示第个叶子节 点。其中（）点。其中（）;2)2)将水印信息加密将水印信息加密,得到水印序列：得到水印序列：,.,.,。用表示第。用表示第 位水印。位水印。()()；3 3）If(If(水印信息大于叶子节点数水印信息大于叶子节点数)退出，提示水印嵌入失败；退出，提示水印嵌入失败；4 4）While(While(水印信息完全被嵌入水印信息完全被嵌入)If(If(第位的水印为第位的水印为1)1)将处的叶子节点变换为父节点的属性将处的叶子节点变换为父节点的属性;Else E

24、lse 处的叶子节点保持不变；处的叶子节点保持不变；5)5)形成带有水印信息的形成带有水印信息的XMLXML文档文档 Extracted Algorithm输入：含水印信息的输入：含水印信息的XMLXML文档，密钥文档，密钥 。输出：水印信息输出：水印信息 。If(XMLIf(XML文档不合法）文档不合法）退出，提示退出，提示XMLXML文档不合法，提取失败；文档不合法，提取失败；While(While(遍历完遍历完XMLXML文档所有节点文档所有节点)If(If(父节点处有属性描述父节点处有属性描述)此处的水印信息位此处的水印信息位1;1;3)3)得到一串数字水印序列得到一串数字水印序列,.

25、,.,；4 4）解密，形成水印信息）解密，形成水印信息;Watermarking BitHASH()a one-way hash function H operates on an input message M of arbitrary length and retruns a fixed length hash value h.ie.h=H(M).Example:SHA1()MD5()SHA1（）函数Watermarking string:湖南大学Watermarking bit:1111001010101100000010101001110000110010100010100100101

26、0001001101110101010000110000111000111011011110110001101100001111000011110101101101010101000011010010001100001001001011010111101000101011011001100110011101100111010111100MD5()函数Watermarking string:湖南大学Watermarking bit:01101100101010100001110000110010110101000100111001010110010100100001011001101100001

27、0011000100010101001100110110000101010000101101000011000011010111011101100011011101110100000101011110010111100Problems1.Watermarking bit position2.Detection&Extraction3.AttacksWatermarking bit position1 must be a leaf;2 can be moved to the fathers attribute;3 random choice;Detection&ExtractionIn wate

28、rmarking the emphasis is on“detection”In watermarking the emphasis is on“detection”rather than“extraction”.Extraction of a watermarkingrather than“extraction”.Extraction of a watermarking(or bits of it)is usually a part of the detection(or bits of it)is usually a part of the detection process but ju

29、st complements the process up to process but just complements the process up to the extent of increasing the ability to convince in the extent of increasing the ability to convince in court.If recovering the watermark data in itself court.If recovering the watermark data in itself becomes more impor

30、tant than detecting the becomes more important than detecting the actual existence of it(actual existence of it(ie ie.yes/no answer).yes/no answer)then this is a drift toward covert communication then this is a drift toward covert communication and pure and pure steganographysteganographyCumulative

31、Binomial probabilityLet b(k;n,p)be the probability that n Bernoulli trials with probabilities p for success and q=1-p for failure result in k successes and n-k failures.Then AttacksA1:elimination of some nodes;A2:addition some nodes;A3:modification of attributesContent WatermarkingThe fact that node

32、s in semi-structures are value-The fact that nodes in semi-structures are value-carrying,means that a watermarking algorithm carrying,means that a watermarking algorithm could make use of their encoding capacity by could make use of their encoding capacity by using traditional watermarking on the in

33、dividual using traditional watermarking on the individual nodes:If a node contains an image then an nodes:If a node contains an image then an image watermarking algorithm could be used for image watermarking algorithm could be used for that node to encode parts of the global that node to encode parts of the global watermarking,similarly if it contains sound,or watermarking,similarly if it contains sound,or video,or text,etc.video,or text,etc.Thank you