entrust technologies europe

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1、SeparabilityandEÆ ien yforGeneri GroupSignatureS hemes(ExtendedAbstra t)?anCamenis harkusi hels??EntrustTe hnologiesEuropeBR
CSr3se urityengineeringagDepartmentofComputerS ien eGlattTower,6th oorUniversityofAarhusCH{8301Glattzentrum,yunkegadeSwitzer

2、landD{8000ArhusC,Denmarkarkus.i helsentrust. om amenis hieee.orgAbstra t.A ryptographi proto olpossessesseparabilityifthepar-ti ipants anhoosetheirkeysindependentlyofea hother.Thisisad-vantageousfromakey-managementaswellasfromase uritypointofview.Thi

3、spaperfo usesonseparabilityingroupsignatures hemes.Su hs hemesallowagroupmembertosignmessagesanonymouslyonthegroup'sbehalf.However,in aseofthisanonymity'smisuse,atrustee anrevealtheoriginatorofasignature.Weprovideageneri fullysepara-blegroupsignatures hem

4、eandpresentaneÆ ientinstantiationthereof.Thes hemeissuitedforlargegroups;thesizeofthegroup'spubli keyandthelengthofsignaturesdonotdependonthenumberofgroupmember.
tseÆ ien yis omparabletothemosteÆ ients hemesthatdonotoerseparabilityandisanorderofmagnitude

5、moreeÆ ientthanapreviouss hemethatprovidespartialseparability.Asasideresult,weprovideeÆ ientproofsoftheequalityoftwodis retelogarithmsfromdierentgroupsand,moregeneral,ofthevalidityofpolynomialrelationsinZamongdis retelogarithmsfromdierentgroups.1
ntrodu

6、 tionultiparty ryptographi proto olsaretypi allypre ededbyasetupphaseinwhi htheinvolvedentitieshoosetheirpubli andse retkeysbesidesothersystem-parameters.ftentheirhoi esdependontheotherentities'hoi es.otonlyfor esthistheentitiestohoosenewkey-pairsforea

7、 h(kindof)proto oltheyparti ipateinbutalsotore- hoosetheirkeysifotherentitiesrenewtheirsorifthesystem-parametersarehanged.Apartfromsu hkey-managementprob-lems,adependen ybetweendierentkeys an ausese urityproblemsaswell.Forinstan e,ifsomeentityhooseweakpa

8、rametersordis loseshis/herse retkeys,otherentities'se urity anbeweakenedaswell.?Currentaddress:
BZuri h,Saumerstrasse4,CH-8803Rus hlikon.??Basi Resear hinComputerS ien e,CenteroftheDanishationalResear hFoun-dation