《计算机专业英语》课件第24章

UnderstandingEncryption

Securityexpertsagreethatcircumspectuseofstrongencryptionisthebestwaytokeepconfidentialdatasecretfrominterloperswhomaystealcomputers,intercepte-mail,orslipthroughcracksinfirewalls.Encryptionisthereal-worldworkhorseofthescienceofcryptography.Itistheprocessofconvertingdataintoaformthatisunintelligiblewithoutthesecretdecryptionkey.

First,let’sgetafewtermsoutoftheway.1Incryptography,afileofanytypethatisn’tencryptediscalledplaintext;encrypteddataiscalledciphertext.Anencryptionalgorithmorcipher,suchasaweakonecalledCaesarCipher,mightreplaceeachcharacterofplaintextbyskippingtwoletterssothatAbecomesD,PbecomesS,ZbecomesC,andsoonthroughoutthealphabet.Thus,plaintextisnowgarbledciphertext.

Ofcourse,thesecurityrenderedbysuchanantiquatedalgorithmisnil.2Modernencryptionalgorithmsarenecessarilymoresophisticatedbecausetheciphertextmayoftenbeprotectinginformationworththousandsormillionsofdollars.3Today’sstrongalgorithms,whichneednotremainsecret,poseamathematicalproblemthatishardtosolvewithoutthecorrectkey.Tocryptographers,“hard”meanscomputingwiththousandsofsystemsandgettingananswerinmonths,years,orsometimesaftertheendoftheuniverse.

Encryptionalgorithmcangenerallybedividedintotwotypes:conventionalalgorithmsandpublic-keyalgorithms.(Thereareothersthathavespecializedfunctions,forinstance,digitalsignatureandkeyagreementalgorithms.)Conventionalalgorithmsaresymmetricalandrelyonthesamekeyforencryptionanddecryption.Theyarebestusedtoencryptfilesonaharddisk.

4Public-keyalgorithms,ontheotherhand,areasymmetrical,usingdifferentkeys,apublickey,andasecretkey,forencryptionanddecryption.Public-keyalgorithmsletyousharefiles,particularlye-mailcorrespondence,withotherusers.Inapublic-keysystem,forinstance,ifZooeywantstosendFrannyanencryptionmessage,FannywouldfirstsendZooeyherpublicKey.ZooeythenusesFranny’spublic-keytoencryptamessagetoher.WhenFrannyreceivesthemessagefromZooey,shecandecryptthemessagewithhersecretkey.

Public-keyencryptionsolvestheproblemofmanagingseveralkeys,butencryptionisslowcomparedtoconventionalencryption.Keymanagementinconventionalencryption,however,isaproblembecauseseveralfilesmaybeencryptedwithdifferentkeys.

Althoughgoodconventionalandpublic-keyalgorithmsarebothconsideredstrong,theirrespectivekeylengthsforsecurityvary.Awhileago,anadhocgroupofcomputerscientistsandcryptographerscontributedtoapaperthatrecommendedakeyofatleast90bitsforsymmetricalgorithmsusedincommercialsecurity.Manydomesticproductsalreadyexceedthatrecommendationandallow128bitkeys,Akeysizeof128bitsmeansthatthereare2128possiblekeys,enoughtofoilabruteforceattack(tryingeverypossiblekey).5Symmetricalgorithmswhosekeysizeis40bitscanbeandhavebeencrackedbyhackers.

Publickeys,however,mustbelarger,becausethemathematicsinanasymmetricalgorithmaredifferent.KeysizesforgoodsecurityusingtheRSApublic-keyalgorithmrangefrom768bitsto2,048bits.6CrackingRSAmeansconfrontingwhatmathematiciansbelievetobethehardproblemoffactoringlargenumbers.NewWordsencryptionn.加密securityn.安全expertn.专家circumspectadj.周到的,周密的confidentialadj.保密的,机密的interceptv.窃听crackv.破译firewalln.防火墙workhorsen.骨干cryptographyn.密码unintelligibleadj.难解的decryptionn.解码encryptv.将……译成密码plaintextn.明文(未加密的电文),明码文本ciphertextn.加密文本algorithmn.算法cipherv.加密skipv.跳过garblev.混淆renderv.交付antiquatev.废弃necessarilyadv.必要地posev.提出cryptographern.破解密码者digitaladj.数字的symmetricaladj.对称的asymmetricaladj.不对称的correspondencen.一致性,通信decryptv.解密respectiveadj.分别的varyv.使多样化contributev.贡献recommendv.推荐exceedv.超过recommendationn.推荐confrontv.面临PhrasesandExpressions

sothat以便divideinto把……分开forinstance例如ontheotherhand另一方面compareto与……比较TheExplanationofDifficultStatements

1.Incryptograghy,afileofanytypethatisn’tencryptediscalledplaintext.

分析:“thatisn’tencrypted”作定语,此处“that”为关系代词,故不可以省略。

句意:在密码学中,没有加密的任何形式的文件都叫做普通文本(也可译为“明文”)。

2.Modernencryptionalgorithmsarenecessarilymoresophisticatedbecausetheciphertextmayoftenbeprotectinginformationworththousandsormillionsofdollars.

分析:“worththousandsormillionsofdollars”为形容词短语作定语,句型“beworthdoingsth./sb.”意为“值得做某事”。句意:现代加密算法必须更为复杂,因为密码文本常为用户保护价值数十万或数百万美元的信息。

3.Today’sstrongalgorithms,whichneednotremainsecret,poseamathematicalproblemthatishardtosolvewithoutthecorrectkey.

分析:“whichneednotremainsecret”和“thatishardtosolvewithoutthecorrectkey”同为定语从句,翻译时可采用“分译法”。句意:今天,强有力的算法无须保密,因为它提出的数学问题在没有正确的密钥情况下是难以解开的。

4.Public-keyalgorithms,ontheotherhand,areasymmetrical,usingdifferentkeys,publickey,andasecretkey,forencryptionanddecryption.

分析:“usingdifferentkeys,publickey,andasecretkey,forencryptionanddecryption”为现在分词作伴随情况的状语。句意:公开密钥算法法则是不对称的,采用不同的密钥,一个公开的密钥和一个秘密的密钥,用来加密和解密。

5.Symmetricalgorithmswhosekeysizeis40bitscanbeandhavebeencrackedbyhackers.

分析:“whosekeysizeis40bits”为定语从句,whose在从句中作定语。

句意:密钥长度为40位的对称算法可能并且已经被黑客破译了。

6.CrackingRSAmeansconfrontingwhatmathematiciansbelievetobethehardproblemoffactoringlargenumbers.

分析:“meandoingsth.”的意思是“意味着”、“有……的意思”,“meantodosth.”的意思是“打算做某事”

句意:破译RSA意味着面临数学家们所认为的问题——分解大量数字因子的难题。GrammarTranslationSkills被动语态的翻译方法

英语中被动语态使用广泛,尤其是科技作品使用更多,而汉语使用面较窄,因此在翻译科技作品时,英语被动语态一般翻译成主动语态。具体有如下翻译方法。

1.把被动句译成主动句

当英语被动句的主语是无生命名词时,常常直译成汉语的主动形式。例如:

Thequalityofthenewproductshasbeengreatlyimproved.这种新产品的质量有了很大的提高。

Thisformulahasalreadybeenmentionedabove.这个公式上面已经提到过。

2.用“将”、“把”、“使”等词译成无主语主动句例如:

ThisisdonebyassignaportnumbertoeveryTCPconnection.这是通过为每个TCP连接分配一个端口号实现的。

Temperatureischangedquicklyfromroomtemperatureto125℃andisheldthereforatleast15minutes.使温度很快从室温升高到125度,并至少保持15分钟。

3.特别突出被动者的译法要特别突出被动者时,把英语的被动句译成汉语的主动句,常用“经过”、“由”、“被”、“受”、“让”、“给”、“靠着”、“遭”、“加以”、“为……所”、“是……的”等词表示。例如:

Waterisusuallyconsideredasbeingacompoundoftwoelements.水通常被认为是由两种元素构成的化合物。

Thequestionwillbeansweredfirst.这个问题总是被首先予以回答。

4.加主动者的译法根据句意加上“人们”、“我们”、“大家”、“有人”等词译成主动句。例如:

Hewasseenbuyinganewwashingmachineinthesupermarket.有人看见他在超级市场买了一台新洗衣机。

Thematterwasveryoftentalkedabout.我们曾多次谈到这件事。

5.把英语的被动句译成汉语因果句例如:

Thethroatisaffectedbyacold.喉咙因患风寒而痛。

Thecropswerebadlydamagedbyaflood.农作物因水灾而毁坏。

6.主语变宾语的翻译将原文中的主语在译文中变为宾语,译为汉语主动语态。例如:

Thistaskmustbefulfilledbyusintime.我们必须及时完成这个任务。

7.常见句型的翻译有些常用句型的翻译方法需要注意，例如：

Itissaidthat据说

Itisknownthat众所周知

Itisbelievedthat大家相信

Itisgenerallyagreedthat人们通常认为

Itisconsideredthat据估计,人们认为

Itisclaimedthat据称,有人宣称

Itisassumedthat假设,假定

Ithasbeenprovedthat已经证明

Itmustbeadmittedthat老实说,必须承认例如:

Ithasbeenprovedthatenergycannotbedestroyed;itcanonlybechangedintootherforms.已经证明,能量是不可能消灭的,只能转换成其它形式。Itisgenerallyrecognizedthatlighthasavastcapacityfortransmittinginformation.一般认为,光传播信息的容量极大。ExercisesⅠ.Fillintheblanksaccordingtothetext:(1)Securityexpertsagreethatcircumspectuseof___________isthebestwaytokeepconfidentialdatasecretfrominterlopers.(2)Incryptography,afileofanytypethatisn’tencryptediscalle______________;encrypteddataiscalled______________.(3)Today’sstrongalgorithms,whichneednotremainsecret,posea__________thatishardtosolvewithoutthecorrectkey.(4)Encryptionalgorithmcangenerallybedividedintotwotypes:______________andpubic-keyalgorithms.(5)______________algorithmsletyousharefiles,particularlye-mailcorrespondence,withotherusers.Ⅱ.Decidewhethereachofthefollowingstatementsistrueorfalseaccordingtothetext:(1)Encryptionistheprocessofconvertingdataintoaformthatisunintelligiblewithoutthesecretdecryptionkey.(2)Modernencryptionalgorithmsarenecessarilymoresophisticatedbecausetheciphertextmayoftenbeprotectinginformationworththousandsormillionsofdollars.(3)Conventionalalgorithmsaresymmetricalandrelyonthedifferentkeyforencryptionanddecryption.(4)Public-keyencryptionsolvestheproblemofmanagingseveralkeys,butencryptionisfastcomparedtoconventionalencryption.(5)Akeysizeof128bitsmeansthatthereare2128possiblekeys,enoughtofoilabrute-forceattack(tryingeverypossiblekey).Ⅲ.TranslatethefollowingsentencesintoChinese:(1)Candidatesarerequiredtopresentthemselves15minutesbeforetheexamination.(2)Attentionshouldbepaidthestudyofminoritynationalities’culture.(3)Itisconsideredofnouselearningatheorywithoutpractice.(4)Althoughgoodconventionalandpublic-keyalgorithmsarebothconsideredstrong,theirrespectivekeylengthsforsecurityvary.(5)WebswitchingisdesignedtoaddresstherequirementsofWebtraffic.Ⅳ.TranslatethefollowingparagraphintoChinese:

Thenumberofbusinesscrimesofalltypesisprobablydecreasingasadirectresultofincreasingautomation.Whenabusinessactivityiscarriedoutwithcomputerandcommunicationssystems,dataarebetterprotectedagainstmodification,destruction,disclosure,misappropriation,misrepresentation,andcontamination.Computersimposeadisciplineoninformationworkersandfacilitateuseofalmostperfectautomatedcontrolsthatwereneverpossiblewhenthesehadtobeappliedbytheworkersthemselvesundermanagementedict.Forexample,acontrolinacomputertodetectalltransactionaboveacertainamountandflagthemforlaterauditworksperfectlyeverytime.Computerhardwareandsoftwaremanufacturesarealsodesigningcomputersystemsandprogramsthataremoreresistanttotampering.ReadingMaterialsComputerCrime(VarietyandExtent)

Computerhavebeenusedformostkindsofcrime,includingfraud,theft,embezzlement,burglary,sabotage,espionage,murder,andforgery,sincethefirstcaseswerereportedin1958.Onestudyof1,500computercrimesestablishedthatmostofthemwerecommittedbytrustedcomputeruserswithinbusinesses—personswiththerequisiteskills,knowledge,access,andresources.Muchofknowncomputercrimehasconsistedofenteringfalsedataintocomputers,whichissimplerandsaferthanthecomplexprocessofwritingaprogramtochangedataalreadyinthecomputer.Withtheadventofpersonalcomputertomanipulateinformationandaccesscomputersbytelephone,increasingnumbersofcrimes—mostlysimplebutcostlyelectronictrespassing,copyrighted-informationpiracy,andvandalism—havebeenperpetratedbycomputerhobbyists,knownas“hackers,”whodisplayahighleveloftechnicalexpertise.Organizedprofessionalcriminalhavebeenattackingandusingcomputersystemsadstheyfindtheiroldactivitiesandenvironmentsbeingautomated.

Therearenovalidstatisticsabouttheextentofcomputercrime.Victimsoftenresistreportingsuspectedcases,becausetheycanlosemorefromembarrassment,lostreputation,litigation,andotherconsequentiallossesthanfromtheactsthemselves.Limitedevidenceindicatesthatthenumberofcomputersinbusinessapplicationswherecrimehastraditionallyoccurred.Thelargestrecordcrimesinvolvinginsurance,banking,productinventories,andsecuritieshaveresultedinlossesoftensofmillionstobillionsofdollars—allfacilitatedbycomputers.NewWordsandExpressions

fraudn.欺骗,欺诈行为embezzlementn.贪污,盗用theftn.偷窃burglaryn.夜盗行为,盗窃sabotagen.(对财产等)故意破坏,破坏活动espionagen.谍报,间谍活动forgeryn.(签字,文件等)伪造,赝品requisitea.必要的,必不可少的adventn.出现,到来trespassvi.非法入侵piracyn.侵犯版权,海盗行为vandalismn.破坏文化行为,破坏(他人或公共)财产hobbyistn.有业余癖好的人Questions(1)WhichkindsofcrimehaveComputerbeenusedfor?(2)Wherehascrimetraditionallyoccurred?ComputerCrime(RemediesandLawEnforcement)

Thenumberofbusinesscrimesofalltypesisprobablydecreasingasadirectresultofincreasingautomation.Whenabusinessactivit