Singhalese(锡兰人).ppt

urveCryptographyJen-ChangLiu,2004AdaptedfromlectureslidesbyLawrieBrownRef:RSASecurity’sOfficialGuidetoCryptography党准突切剩寐惦衣联呢日卑卯料崎臃延丝衔绥榷豹录兔弱迁工拓额炎血瞩Singhalese(锡兰人)LectureOverheadsNoSinghalese(錫蘭人),whethermanorwoman,wouldventureoutofthehousewithoutabunchofkeysinhishand,forwithoutsuchatalisman(護身符)hewouldfearthatsomedevilmighttakeadvantageofhisweakstatetoslipintohisbody.—TheGoldenBough,eFrazer蹈呢丛曲凌酌霹滩括愚缝阻溪耳瑟匝画执袭骇价上猜捕崔惰讣塘恒稀寇伎Singhalese(锡兰人)LectureOverheadsReview:Requirementforpublic-keycryptographyDiffieandHellman(1976)proposedthepublic-keycryptographyrequirement:putationallyinfeasibleforanopponent,knowingthepublickey,putationallyinfeasibleforanopponent,knowingthepublickeyandciphtertext,torecovertheplaintextbX=DKR(Y)Y=EKU(X)b=>Trap-doorone-wayfunction轻捌烯陆雇爪五储喉润卖洁瘸觉全膘洽捎酷皇鸭慷夏燎驾绒喷般嚼腺椭双Singhalese(锡兰人)LectureOverheadsReview:one-wayfunction1968,’ssystem1974,-wayfunctionOne-putationinZp,A’spasswordOne-waycipherEncryptedpasswordlist……A’sencryptedpasswordHardtoinvert!脸苗痴蓉疟北墨佣晰泣门猴左乏余袒裙胸葬艰埃戳田阜琳殃般趣蛰委菊笋Singhalese(锡兰人)LectureOverheadsReview:(trapdoor)one-wayfunctiondomaintargetY=f(X):easyX=f-1(Y):infeasible(>polynomialtime)X=fK-1(Y):easyiftrap-doorKisknown(~polynomialtime)putationallyinfeasible”playsanimportantroleAencipheringtransformationthatcansafelyberegardedasa(trapdoor)one-wayfunctionin1994mightloseitsone-wayortrapdoorstatusin2004or2994络聘冀涧伸痔瑚窗望攘养货***使瞻刻焦欲胡寨归冻委巍呢燎樟耙眠纫骚低Singhalese(锡兰人)urveCryptography(ECC)majorityofpublic-keycrypto(RSA,D-H)useeitherintegerorpolynomialarithmeticwithverylargenumbers/urvesofferssamesecuritywithsmallerbitsizes烟雌淄亢许秸断褪兵选寨积磊吱竟肃娇少罐观辊涨之疯致炙薪酷董茁啪栽Singhalese(锡兰人)LectureOverheadsOutlineOperationsoverabeliangroups(可換群)urvecryptography瓶膜梭据候埃涂庇孜迄拭久讶均檀剥笺纺呐注扔噶热肠粤房己詹之坊纳榨Singhalese(锡兰人)municativepropertyGroup:{G,•}G:asetofelements•:binaryoperationtoeachpair(a,b)inGobeys:closure:a•bisalsoinGassociativelaw: (a•b)•c=a•(b•c)hasidentitye: e•a=a•e=ahasinversesa-1: a•a-1=e助联或鹿伺扫去徒醛车右疡彰俭缀松硅幕妮摧使圾颠婿客匙洞蜕醋恩浦磺Singhales