條件提交樣例其它英文翻譯

CHAPTER396unlimitedaccessincludestheabilitytochangethe ’spasswordsaccessOpeningthe withthecorrectuserpassword(oropeningadocu-mentthatdoesnothaveauserpassword)allowsadditionaloperationstoperformedaccordingtotheuseraccesspermissionsspecifiedinthedocu-ment’sencryptiondictionary.Accesspermissionsarespecifiedintheformofflagscorrespondingtotheoperations,andthesetofoperationstowhichtheycorresponddependsinonthesecurityhandler’srevisionnumber(alsostoredintheencryptionary).Iftherevisionnumberis2orgreater,theoperationstowhichusercanbecontrolledareasModifyingthe’sCopyingorotherwiseextractingtextandgraphicsfromtheingextractionforaccessibilitypurposes(thatis,tomakethecontentsoftheaccessiblethroughassistivesuchasscreenBrailleoutputdevices;seeSection10.8,“AccessibilityAddingormodifyingtextannotations(see“TextAnnotations”onpage574)andinctiveformfields(Section8.6,“InctiveForms”)PrintingtheIfthesecurityhandler’srevisionnumberis3orgreater,useraccesstothefollow-ingoperationscanbecontrolledmoreFillinginforms(thatis,fillinginexistingin ctiveformfields)andsigning (whichamountstofillinginexistingsignaturefields,atype ctiveformAssemblingthe :inserting,rotating,ordeletingpagesandnavigationelementssuchasbookmarksorthumbnailimages(seeSection“-LevelPrintingtoarepresentationfromwhichafaithfuldigitalcopyofthePDFcon-tentcouldbegenerated.Disallowingsuchprintingmayresultindegradationoutputquality(afeatureimplementedas“PrintAsImage”inInaddition,revision3enablestheextractionoftextandgraphics(insupportofaccessibilitytodisabledusersorforotherpurposes)tobecontrolledseparay.SECTION3.597Beginningwithrevision4,thestandardsecurityhandlersupportscryptcryptfil-ter(seeTable3.23)andcryptfiltersnamedStdCFwhosedictionariescontainaCFMvalueofV2andanAuthEventvalueofNote:Oncethehasbeenopenedanddecryptedsuccessfully,theapplicationhasaccesstotheentirecontentsofthe.Thereisnothinginher-entinPDFencryptionthatensthepermissionsspecifiedthecryptiondictionary.ItisuptotheimplementorsofPDFviewerapplicationsrespecttheintentofthe creatorbyrestrictinguseraccesstoanencryptedPDFfileaccordingtothepermissionscontainedintheNote:PDF1.5introducesanewsetofaccesspermissionsthatdonotrequiretobeencrypted;seeSectionStandardEncryptionTable3.19showstheencryptiondictionaryentriesforthestandardsecurityhandler(inadditiontothoseinTable3.18onpage92).TABLE3.19AdditionalencryptiondictionaryentriesforthestandardsecurityhandlerKEYTYPERnumber(Required)Anumberspecifyingwhichrevisionofthestandardsecurityhandlershouldbeusedtointerpretthisdictionary.TherevisionnumbershouldiftheisencryptedwithaVvaluelessthan2(seeTable3.18)anddoesnothaveanyoftheaccesspermissionsset(viathePentry,below)thataresion3”inTableif isencryptedwithaVvalueof2or3,orhas“Revision3”accesspermissionsset.iftheisencryptedwithaVvalueofOstring(Required)A32-bytestring,basedonboththeowneranduserpasswords,thatisusedincomputingtheencryptionkeyandindeterminingwhetheravalidownerpasswordwasentered.Formoreinformation,see“EncryptionKeyAlgorithm”onpageandwordAlgorithms”onpageUstring(Required)A32-bytestring,basedontheuserpassword,thatisusedindeterminingwhethertoprompttheuserforapasswordand,ifso,whetheravaliduserorownerpass-wordwasentered.Formoreinformation,see“PasswordAlgorithms”onpageCHAPTER398ThevaluesoftheOandUentriesinthisdictionaryareusedtodetermineerapasswordenteredwhenthe isopenedisthecorrectownerword,userpassword,orThevalueofthePentryisanunsigned32-bitintegercontainingasetofspecifyingwhichaccesspermissionsshouldbegrantedwhentheisopenedwithuseraccess.Table3.20showsthemeaningsoftheseflags.Bittionswithintheflagwordarenumberedfrom1(low-order)to32(high-order);a1bitinanypositionenablesthecorrespondingaccesspermission.Whichbitsaremeaningful,andinsomecaseshowtheyareinterpreted,dependsonthehandler’srevisionnumber(specifiedintheencryptiondictionary’sRNote:PDFintegerobjectsinfactarerepresentedinternallyin-plementform.Sinceallthehigh-orderflagbitsinthedictionary’sPvaluearerequiredtobe1,thevaluemustbespecifiedasanegativeinteger.Forexample,assumingrevision2ofthesecurityhandler,thevalue-44al-lowsprintingandcopyingbutdisallowsmodifyingthecontentsTABLE3.20UseraccessPinteger(Required)Asetofflagsspecifyingwhichoperationsarepermittedwhenthe openedwithuseraccess(seeTableBITPOSITION1–2;mustbe3(Revision2)Print (Revision3)Printthe (possiblynotatthehighestqualitylevel,dependingonwhetherbit12isalsoset).4Modifythecontentsofthe byoperationsotherthanthosecontrolledbybits6,9,and11.5(Revision2)Copyorotherwiseextracttextandgraphicsfromthe,includingextractingtextandgraphics(insupportofac-cessibilitytodisabledusersorforotherpurposes).(Revision3)Copyorotherwiseextracttextandgraphicsfromthebyoperationsotherthanthatcontrolledbybit10.KEYTYPESECTION3.599EncryptionKeyAsnotedearlier,onefunctionofasecurityhandleristogenerateankeyforuseinencryptinganddecryptingthecontentsofa.Givenpasswordstring,thestandardsecurityhandlercomputesanencryptionkeyshowninAlgorithmAlgorithm3.2ComputinganencryptionPadortruncatethepasswordstringtoexactly32bytes.Ifthepasswordstringismorethan32byteslong,useonlyitsfirst32bytes;ifitisless32bytespaditbyappendingtherequirednumberofadditionalbytesfromtheofthefollowingpadding<28BF4E5E4E758A4164004E56FFFA012E2E00B6D0683E802F0CA9FE6453697AThatis,ifthepasswordstringisnbyteslong,appendthefirst32nbytesofthepaddingstringtotheendofthepasswordstring.Ifthepasswordstringisempty6Addormodifytextannotations,fillinin ctiveformfields,and,ifbit4isalsoset,createormodifyin ctiveformfields(includingsignaturefields).7–8;mustbe9(Revision3only)Fillinexistingin ctiveformfields(includingsignaturefields),evenifbit6isclear.10(Revision3only)Extracttextandgraphics(insupportofaccessibil-itytodisabledusersorforotherpurposes).11(Revision3only)Assemblethe(insert,rotate,ordeletepagesandcreatebookmarksorthumbnailimages),evenifbit4is12(Revision3only)Printthe toarepresentationfromwhichafaithfuldigitalcopyofthePDFcontentcouldbegenerated.Whenthisbitisclear(andbit3isset),printingislimitedtoalow-levelrepresentationoftheappearance,possiblyofdegradedquality.(Seeimplementationnote20inAppendixH.)13–32(Revision3only);mustbe1.BITPOSITIONMEANINGCHAPTER3100(zero-length),meaningthereisnouserpassword,substitutetheentirestringinitsInitializetheMD5hashfunctionandpasstheresultofstep1asinputtothisfunc-Passthevalueoftheencryptiondictionary’sOentrytotheMD5hash(Algorithm3.3showshowtheOvalueisTreatthevalueofthePentryasanunsigned4-byteintegerandpassthesebytestotheMD5hashfunction,low-orderbytePassthefirstelementofthefile’sfileidentifierarray(thevalueoftheIDentryinthe’strailerdictionary;seeTable3.13onpage73)totheMD5(Revision3only)Ifmetadataisnotbeingencrypted,pass4byteswiththevalue0xFFFFFFFFtotheMD5hashFinishthe(Revision3only)Dothefollowing50times:TaketheoutputfromtheMD5hashandpassitasinputintoanewMD5SettheencryptionkeytothefirstnbytesoftheoutputfromthefinalMD5hash,wherenisalways5forrevision2butforrevision3dependsonthevalueoftheen-cryptiondictionary’sLengthThisalgorithm,whenappliedtotheuserpasswordstring,producesthetionkeyusedtoencryptordecryptstringandstreamdataaccordingtorithm3.1onpage94.Partsofthisalgorithmarealsousedinthealgorithmsdescribedbelow.PasswordInadditiontotheencryptionkey,thestandardsecurityhandlermustprovidethecontentsoftheencryptiondictionary(Tables3.18onpage92and3.19on97).ThevaluesoftheFilter,V,Length,R,andPentriesarestraightforward,butthecomputationoftheO(ownerpassword)andU(userpassword)entriesquiresfurtherexnation.Algorithms3.3through3.5showhowthevaluestheownerpasswordanduserpasswordentriesarecomputed(withseparatesionsofthelatterforrevisions2and3ofthesecurity396無限包括改變文件口令和的能力戶口令的文件，這取決于文件包含的。對以相應的形式詳細說明并且操作配置符合依安全處理機的修訂號而定（同樣在加密技術中。如果修訂號是2或者更大下列用戶操作受從文件中或另外取出文本圖形包括取出可達目（即通過協(xié)助技術如濾網(wǎng)顯10.8（574（8.6打印文本：插入，循環(huán)交替，或刪除記錄，創(chuàng)造導航元件，如書簽或簡略見8.2節(jié)“文——平交路口，打印可能生成一種表現(xiàn)PDF內容的正確數(shù)字拷貝打印可能導致輸出設備質量的降級（在閱讀器中一種像以“打印”的工具），3.597從修訂本4開始，標準安全處理機支持隱藏過濾器（見3.5.4隱藏過濾器同一隱藏過濾器支持有限（見3.23表格）名為StdCF的隱藏過濾器詞典包括V2的DocOpen注意：一旦文件被打開和成功破譯，觀察者便可申請到完整的文件內容。在加