The content of the invention
The brief overview of one or more aspects given below is to provide to the basic comprehension in terms of these.This general introduction is notThe extensive overview of all aspects contemplated, and it is also non-to be both not intended to identify the key or decisive key element of all aspectsAttempt to define the scope in terms of any or all.Its unique purpose is to provide the one of one or more aspects in simplified formA little concepts think the sequence of more detailed description given later.
According to an aspect of the present invention there is provided a kind of method for creating shielded digital document, including：To the numberWord document is parsed；The digital document is changed into tiff image file from unprocessed form；The of the tiff image fileFirst customized label defined in one image file directory IFD；Unprocessed form digital document is stored in the first self-defined markIn label；And the embedded watermark in the view data of the tiff image file.
In one example, the unprocessed form of the digital document is Word, Excel, PowerPoint, html web page, textOne of file format.
In one example, the digital document is stored in into first customized label includes：To unprocessed form numeralDocument performs compression；Unprocessed form digital document after compression is encrypted；And the unprocessed form numeral after encryption is literaryShelves are stored in first customized label.
In one example, this method also includes：Second is self-defined defined in the first IFD in the tiff image fileLabel；And the classification information of the digital document is stored in second customized label.
In one example, the embedded watermark includes in the view data of the tiff image file：The watermark is performedEncryption and disorder processing；Dct transform is performed to the view data；According to watermark embedding strategy in the frequency domain of the view data it is embeddingEnter encrypted and scramble watermark；And idct transform is performed to the view data after embedded watermark.
There is provided a kind of method for browsing shielded digital document, the numeral according to another aspect of the present inventionDocument is included in tiff image file, and this method includes：Recover watermark from the view data of the tiff image file；TestThe recovered watermark of card；If being proved to be successful, the image of the tiff image file is played；And if authentication failed, from thisUnprocessed form digital document is read in the first customized label in first image file directory IFD of tiff image file.
In one example, the unprocessed form digital document bag is extracted from the first customized label of the tiff image fileInclude：The unprocessed form digital document is decrypted；And the unprocessed form digital document after decryption is performed decompression to obtainObtain original digital document.
In one example, recovering the watermark from the view data of the tiff image file includes：To the view dataPerform dct transform；The watermark is extracted from the frequency domain of the view data according to watermark extracting strategy；And the water to being extractedPrint performs decryption and anti-disorder processing to recover watermark.
In one example, verify that recovered watermark includes：The watermark recovered and original watermark are compared；IfBoth are consistent, then are proved to be successful, otherwise authentication failed.
In one example, this method also includes：The second customized label from the first IFD of the tiff image fileThe middle classification information for reading the digital document.
According to another aspect of the invention there is provided a kind of service end for being used to create shielded digital document, including：Document resolver, to be parsed to the digital document；Format converter, the digital document to be converted from unprocessed formInto tiff image file；Customized label write device, to fixed in the first image file directory IFD of the tiff image fileAdopted first customized label, and the digital document is stored in first customized label；And water mark embedding device, toEmbedded watermark in the view data of the tiff image file.
In one example, the unprocessed form of the digital document is Word, Excel, PowerPoint, html web page, textOne of file format.
In one example, the service end also includes compression and encryption equipment, to perform compression and to pressure to the digital documentDigital document after contracting is encrypted, and wherein the digital document is stored in the first self-defined mark by the customized label write deviceLabel include the digital document after encryption being stored in first customized label.
In one example, customized label write device also defined in the first IFD of the tiff image file second fromLabel is defined, and the classification information of the digital document is stored in second customized label.
In one example, water mark embedding device insertion watermark includes：Encryption and disorder processing are performed to the watermark；To the figureAs data perform dct transform；According to the watermark of watermark embedding strategy embedded encrypted and scramble in the frequency domain of the view data；And idct transform is performed to the view data after embedded watermark.
There is provided a kind of client for being used to browse shielded digital document, the number in accordance with a further aspect of the present inventionWord document is included in tiff image file, and the client includes：Watermark detector, to the figure from the tiff image fileAs recovering watermark in data, and verify recovered watermark；And image viewer, should to be played in watermark verification successThe image of tiff image file；And customized label reader, to the first image file mesh from the tiff image fileRecord and unprocessed form digital document is read in the first customized label in IFD.
In one example, the client also includes decompression and decipher, to be carried out to the unprocessed form digital documentDecryption, and the unprocessed form digital document after decryption is performed decompression to obtain original digital document.
In one example, the watermark detector, which recovers watermark, includes：Dct transform is performed to the view data；According to watermarkExtract strategy and the watermark is extracted from the frequency domain of the view data；And decryption is performed to the watermark extracted and random place is invertedManage to recover watermark.
In one example, the watermark detector verifies that recovered watermark includes：By the watermark recovered and initial conditionPrint is compared；If both are consistent, it is proved to be successful, otherwise authentication failed.
In one example, the customized label reader also from second in the first IFD of the tiff image file fromDefine the classification information that the digital document is read in label.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.Note, it is below in conjunction with accompanying drawing and specifically realIt is only exemplary to apply the aspects of example description, and is understood not to carry out any limitation to protection scope of the present invention.
TIFF（TIF）It is the file format based on mark, being widely used in will to picture qualityAsk the storage and conversion of higher image.GIFf image file format designs to store scanner image earliest, canTo handle black and white, gray scale and coloured image, when storing true color image as BMP forms, RGB is directly stored trichromaticColor value and without using palette.Because its flexible structure and pardon is big, it has turned into a kind of mark of image file formatStandard, most picture systems all support this form.The image file of tiff format is conveniently to check first, is supported" photo viewer " that windows operating systems are carried checks picture material.The maximum color depth of the image file of tiff format is32, very fine and smooth image color can be showed.The image file of tiff format also has two important features, and one is to support multipageImage, two be that the maximum feature of tiff image form is favorable expandability, and file structure is supported the self-defined of label field and read.JustIt is the two features based on tiff image form, the present invention proposes a kind of general, flexible digital document protection scheme.
Fig. 1 shows the schematic diagram of the file structure of tiff format image file.GIFf format image file is generally comprisedThree key elements, i.e. image file head（IFH）, image file directory（IFD）And directory entry（DE）And view data, such as figure instituteShow.Each tiff image file is started with the IFH of 8 bytes, and IFH is first data structure in tiff file, in imageFile architecture it is top.This structure is only in a tiff file, there is fixed position.IFH is containedNecessary information needed for the correct other parts for explaining tiff file, such as IFH has the pointer for pointing to first IFD, such as schemesIt is shown.IFD contains the various information of image, while also including the pointer of a sensing actual image data.As illustrated, everyIndividual IFD includes multiple DE, and one label of each DE correspondences, these DE identify size, resolution ratio, color depth of tiff image etc.Each attribute.Similarly, each DE can have a pointer（For example, offset）To point to associated data field opening hereofBeginning position, and provide data type and length, as shown in the figure.This file structure allows data field to be positioned at appointing for fileIt is where square, and can be random length, therefore file format is very flexible.The standard mark defined except tiff image filespecSign outside attribute, customized label can also be used to identify special image attributes as needed.Because an IFD only identifies oneThere can be multiple images in all tag attributes of image, a tiff file, so, there are several pages of figures in a tiff filePicture, will be to that should have several IFD.
In view of the These characteristics of tiff format image file, according to an aspect of the present invention, can be by electronic document filesEvery page be recorded as a width tiff image, correspond to an IFD.Shown because the content of electronic document is converted into image,So as to effectively prevent the duplication to editable document content and reuse.Furthermore it is possible in an IFD（Such as the first IFD）In it is fixedAdopted first customized label, and original electronic document is compressed and encrypted, it is then store in first customized labelIn.Thus, when the need for the user having permission is present to the access of original document or editor, original document can be extracted.RootAccording to another aspect of the present invention, the second customized label defined in the IFD, and by the electronic document contentClassification information is stored in second customized label.It is well known that the retrieval and abnormal classification for picture material are difficult, becauseThis electronic document is after tiff image file is converted into, and direct retrieval and classification for the document become hardly may be usedOK.In the present invention, by the way that the classification information of document is stored in customized label, user can read in search fileThe classification information stored in the customized label, so as to easily realize the retrieval and classification to document.
Digital watermarking is in digital media information（Such as image, sound, video）The middle some digital informations of addition, to protectProtect the copyright of Digital Media, it was demonstrated that the real reliability of product, tracking is pirate or provides the additional information of product.Watermark informationIt is embedded in bearer documents, the sense organ and integrality of original document is not influenceed.According to resistivity of the digital watermarking to attack, numberWord watermark can be divided into：Multipurpose watermarking, fragility watermark, half fragility watermark.Multipurpose watermarking is mainly used in digital pictureIntellectual property protection, prevent from illegally obtaining image file, to modification have stronger robustness；Fragility watermark then mainly shouldUsed in the integrality and Trusting eBusiness of picture material, there is stronger sensitiveness to modification；Half fragility watermark Ze Keyi areasPoint accidentally modification and malice is distorted, and only distorts more sensitive to malice.
According to another aspect of the present invention, water can be embedded in the view data for the tiff image file being converted toPrint, such as fragility watermark.Thus, if the image in tiff image file is changed, what is be embedded by detecting is brittleProperty watermark, the integrality of picture material and credibility can be verified.When detecting the image quilt in tiff image fileWhen distorting, possess the user of due authority and can obtain and consulted and editing and processing by the original document file of protection document.
Fig. 2 shows the schematic diagram of digital watermarking system according to an aspect of the present invention.As shown in Fig. 2 watermaking systemIncluding water mark embedding device 210 and watermark detector 220.In one embodiment, water mark embedding device 210 can be included in for creatingIn the service end of shielded electronic document, and watermark detector 220 can be included in for browsing shielded electronic documentClient in.Water mark embedding device 210 may include pretreatment module 212.Pretreatment module 212 can use Arnold disorder processingsWith Logistic chaos encryption Processing Algorithms, watermarking images to be embedded are encrypted and disorder processing, to strengthen watermark figureThe security of picture.Embedded module 214 is input into by the watermark encrypted with scramble.Embedded module 214 also receives host image,Such as view data of tiff image file, and dct transform processing can be carried out to view data, view data is become from spatial domainChange to frequency domain.Then, encrypted and scramble can be embedded according to watermark embedding strategy in the frequency domain of view data by being embedded in module 214Watermark, and idct transform is performed to the view data after embedded watermark, thus obtains the image containing watermark.
Image containing watermark may be by various attacks, and such as image is distorted.Therefore, recipient user can be by rightThe detection of watermark is verified come integrality and feasibility to picture material.Extraction module 224 in watermark detector 220 canDct transform is performed to view data first, then can be according to watermark extracting strategy by view data from spatial transform to frequency domainWatermark is extracted from the frequency domain of view data.The watermark extracted can be input into anti-pretreatment module 222, the anti-pretreatmentModule 222 can be carried out using the anti-disorder processings of Arnold and the ignorant encryption algorithm of Logistic back mixing to the watermark signal of extractionDecryption and anti-disorder processing, to recover watermark.Although being not shown, watermark detector 220, which may also include, to be recoveredThe module that watermark is compared with original watermark, to be verified to the watermark recovered.If both are consistent, verify intoWork(, represents that view data is not tampered with, otherwise authentication failed, and view data may be tampered.
Fig. 3 shows the flow of the method performed by the service end of file protection system according to an aspect of the present inventionFigure.In step 302, digital document is parsed.Pending file is fed as input to the service of file protection systemEnd, service end recognizes the file type of digital document according to the suffix name of input file, and calls corresponding analyzing component documentData, are that work is ready in follow-up form conversion.Can be by the text of multiple format according to the file protection system of the present inventionFiles are converted into multipage tiff image file, mainly including common Word, Excel, PowerPoint and html web page andDigital document of text formatting etc..Corresponding processing assembly can be added for the processing for increasing document format newly, to cause documentProtection system possesses good autgmentability in terms of accessible document format.
In step 304, the digital document is changed into tiff image file from unprocessed form.Thus, original figure documentEditable sensitive information as on each page image of tiff image file picture material be shown.Before conversionDocument format, because image file is not easy to enter edlin to sensitive information, can prevent in document sensitive information it is directDistort and reuse.In some instances, form conversion, which may also include, first shows the data after parsing according to set formShow to come, the display content of each page is corresponding to one page image in tiff image file.Thus, user can pass through formSet to adjust the page display content of document, so as to for example, when user browses shown document, by grabbing can shield currentlyThe page and current page display content is converted into one page image in tiff image file, also can be by the way that document file page be enteredRow batch grab screen and by the Content Transformation of whole document into the multi-page pictures in tiff image file.In this way, after conversionEvery page of image of tiff image file may correspond to the respective page display content of the document shown according to set form.This hairBright form conversion includes but is not limited to above-mentioned form conversion regime, and those skilled in the art will appreciate that, can using it is anyDocument data after parsing is converted into tiff image file format by the document format conversion regime known.
In step 306, with write-in customized label defined in obtained tiff image file.In one embodiment, may be usedWith the first customized label defined in the specific IFD in the tiff image file, and can be by the digital document of unprocessed formIt is stored in first customized label.Specifically, a tag number example defined in the first IFD of tiff image fileSuch as be 42222 and storage class be byte arrays customized label.For the ease of safely and effectively backing up store document fileOriginal copy, more preferably, can also storage unprocessed form digital document before, digital document is compressed to reduce tiff imageThe size of backup file is stored in customized label, for example, the efficient lossless being combined with Huffman encoding can be encoded using LZWCompression algorithm is compressed to document files.Then, the document after compression can be encrypted, for example, to the document after compressionIt is encrypted using 3DES symmetric encipherment algorithms.Finally, the digital document of the unprocessed form after encryption is stored in above-mentionedIn customized label.In another embodiment, the second self-defined mark defined in the specific IFD of the tiff image fileLabel, and the classification information of the digital document can be stored in second customized label.Specifically, can be in tiff imageA tag number is, for example, 42220 defined in first IFD of file and storage class is the customized label of text type, by thisClassification information is stored in the customized label.
In step 308, the embedded watermark in the view data of the tiff image file.For example, the watermark can be brittleProperty watermark.Fragility watermark to picture material modification have stronger sensitiveness, can be used for picture material integrality andCredible checking.Specifically, encryption and disorder processing can be performed to watermark first, then DCT is performed to the view data and is becomeChange to be transformed to frequency domain, then according to the water of watermark embedding strategy embedded encrypted and scramble in the frequency domain of view dataPrint, finally performs idct transform to be switched back to spatial domain to the view data that embedded in watermark again.
Thus, shielded digital document is created, in the shielded digital document, the sensitivity of original document fileInformation is visible by user of picture material, while having the effect spread information content, because picture material is not easy to editor, preventsDirectly distorting and reuse to sensitive information., can be by the detection of watermark in addition, in the case where view data is tamperedIt was found that view data is distorted, the user having permission still can by reading to customized label in tiff image file comeObtain original document file.
Fig. 4 shows the flow of the method performed by the client of file protection system according to an aspect of the present inventionFigure.In step 402, watermark is recovered from the view data of tiff image file.Specifically, the view data can be held firstRow dct transform is so that it from spatial transform to frequency domain, then to be extracted according to watermark extracting strategy from the frequency domain of the view dataWatermark, then the watermark extracted is performed decryption and anti-disorder processing to recover watermark., can be to being recovered in step 404Watermark is verified.Specifically, the watermark recovered and original watermark can be compared, if both are consistent, verified intoWork(, otherwise authentication failed.
If being proved to be successful, method advances to step 406, wherein can play the image of the tiff image file.As above instituteState, fragility watermark has stronger sensitiveness for distorting, therefore, can be with the case where fragility watermark is not destroyedThink that the picture material in tiff image file is genuine and believable, thus the image of the tiff image file can be played for userBrowse.If authentication failed, method marches to step 408.The authentication failed of fragility watermark shows that picture material is tampered, byThe present image of this tiff image file is insincere.In one example, the prompting that image may be tampered can also be provided.CauseThis, the user having permission can read original figure document from the customized label in the specific IFD of tiff image file.ToolBody, original lattice can be read from the first customized label in the first image file directory IFD of the tiff image fileFormula digital document.Byte array types for example can be read in 42222 customized label from the tag number in the first IFDUnprocessed form digital document.The judgement of authority can be realized by requiring user's offer password.More preferably, the unprocessed form numberWord document is compressed and encrypted.In this case, the unprocessed form digital document of extraction can be decrypted, then to decryptionDocument afterwards performs decompression to obtain original digital document.In another embodiment, can also be from the tiff image fileThe first image file directory IFD in the second customized label in read the classification information of the digital document.Due to original textShelves are after tiff image file is converted into, and retrieval of the user to tiff image content is more inconvenient, therefore the user having permissionThe retrieval of document content can be realized by the classification information extracted in customized label.
Fig. 5 shows the service end of file protection system according to an aspect of the present invention and the block diagram of client.As schemedShown, file protection system 500 includes service end 510 and client 520.Service end 510 can perform the stream described in Fig. 3Journey, and client 520 can perform the flow described in Fig. 4.Service end 510 may include document resolver 511, for holdingThe parsing of row digital document.The document resolver 511 can be using modularity design, easily to extend the file for needing to supportForm.Document data after parsing can be converted into tiff image file format by format converter 512.In some instances, latticeFormula converter 512 can also show the data after parsing according to set form, then by grabbing screen current pageAnd current page display content is converted into one page image in tiff image file, also can be by the way that document file page be criticizedAmount grab screen and by the Content Transformation of whole document into the multi-page pictures in tiff image file.Format converter 512, which can be used, appointsDocument data after parsing is converted into tiff image file format by what known document format conversion regime.Customized label is writeEnter device 514 can defined in tiff image file and write-in customized label.For example, customized label write device 514 can beA tag number is, for example, 42222 defined in first IFD of tiff image file and storage class is the self-defined of byte arraysThe digital document of unprocessed form, is then written in the customized label by label.Server 510 may also include compression and encryptDevice 513, compresses and encrypts for being performed to unprocessed form digital document, for example can be using LZW codings and Huffman encoding phaseWith reference to efficient lossless compression algorithm document files is compressed, and to the document after compression use 3DES symmetric encipherment algorithmsIt is encrypted.In this case, customized label write device can write compressed and encryption in above-mentioned customized labelUnprocessed form digital document.Service end 510 may also include water mark embedding device 515.Water mark embedding device 515 can be in tiff image textEmbedded watermark, for example, be embedded in fragility watermark in the view data of part.Specifically, water mark embedding device 515 can be held to watermark firstRow encryption and disorder processing, then dct transform is performed to be transformed to frequency domain to the view data, plan is then embedded according to watermarkThe watermark of embedded encrypted and scramble slightly in the frequency domain of view data, is finally performed to the view data that embedded in watermark againIdct transform is to be switched back to spatial domain.The concrete composition of water mark embedding device 515 is carrying out retouching in detail above in association with Fig. 2State.
Client 520 may include watermark detector 521, for recovering water outlet from the view data of tiff image filePrint and it is verified.Specifically, watermark detector 521 can first to the view data perform dct transform with by its fromThen spatial transform extracts watermark according to watermark extracting strategy to frequency domain from the frequency domain of the view data, then to being extractedWatermark perform decryption and anti-disorder processing to recover watermark.Watermark detector 521 can also by the watermark recovered with it is originalWatermark is compared, if both are consistent, is proved to be successful, otherwise authentication failed.The concrete composition of watermark detector 521 is upperText is described in detail with reference to Fig. 2.
Client 520 may also include image viewer 522 to play the image of tiff image file.For example, picture browsingDevice 522 can play the image of tiff image file in the case of watermark verification is successful.User can be by browsing tiff imageTo consult the content of digital document, the image viewer 522 supports the played in order of tiff image sequence and random selection to play,Support the zoom and moving operation to image views.Client may also include customized label reader 523 for readingTake customized label.For example, when user inputs password by Authority Verification, customized label reader 523 can scheme from TIFFUnprocessed form digital document is read in the first customized label in first IFD of picture file.The unprocessed form digital document canIt can be compressed and encrypted, decompression and decipher 524 can be decrypted and decompress to the unprocessed form digital document, withObtain original document files.Customized label reader 523 can also be made by oneself from second in the first IFD of tiff image fileThe classification information of the digital document is read in adopted label, in order to be retrieved to document content.
Although for make explanation simplify the above method is illustrated and is described as a series of actions, it should be understood that and understand,The order that these methods are not acted is limited, because according to one or more embodiments, some actions can occur in different orderAnd/or with from it is depicted and described herein or herein it is not shown and describe but it will be appreciated by those skilled in the art that otherAction concomitantly occurs.
It is for so that any person skilled in the art all can make or use this public affairs to provide of this disclosure be previously describedOpen.Various modifications of this disclosure all will be apparent for a person skilled in the art, and as defined herein generalSuitable principle can be applied to spirit or scope of other variants without departing from the disclosure.Thus, the disclosure is not intended to be limitedDue to example described herein and design, but it should be awarded and principle disclosed herein and novel features phase oneThe widest scope of cause.