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kerberos_version1

kerberos_version1 cryptography

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kerberos_version1

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  1. KERBEROS • PRESENTEDBY- • ARADHANA KUSHWAHA • Reg No. 2018CA37 • MCA, 4TH SEMESTER • MNNIT ALLAHABAD VERSION - 1

  2. CONTENT •WhatisKerberos? •WhyKerberos? •Kerberosdesign • Working of Kerberos •ApplicationofKerberos •AttacksonKerberos

  3. WHATISKERBEROS? •Literalmeaning:InGreekmythology,kerberosisamulti-headeddog(usuallythree)whichgaurdstheentranceofHades. •TechnicallyKerberosisanauthenticationprotocolimplementedonProjectAthenaatMIT •Athenaprovidesanopennetworkcomputingenvironment •Eachuserhascompletecontrolofitsworkstation •Buttheworkstationscannotbetrustedcompletelytoidentifyitsuserstothenetworkservices •Kerberosactsasathirdpartyauthenticator -Helpstheusertoproveitsidentitytothevariousservicesandviceversa •Usessymmetricalcryptographicalgorithms (privatekeycryptosystems) –Samekeyisusedforencryptionaswellasdecryption –UsesDES(DataEncryptionStandard)

  4. WHYKERBEROS? •Authenticationisakeyfeatureinamulti-userenvironment. •Sendingusernamesandpasswordsoverthenetworkisnotsecure. •Eachtimeapasswordissentinthenetwork,thereisachanceforinterception. Problem:Cannottrustworkstationtoidentify theiruserscorrectlyinanopendistributedenvironmentSolution: –Buildingelaborateauthenticationprotocolsateachserver –Acentralizedauthenticationserver(Kerberos)

  5. KERBEROSDESIGN •EveryUserhasapassword. •Everyservicehasapassword. •Passwordareneversentacrossthenetworkincleartext(orstoredinmemory) •Usermustidentifyhimselfonceatthebeginningofaworkstationsession(loginsession) •TheonlyentitythatknowsallthepasswordsistheAUTHENTICATIONSERVER(AS)•EveryusersharesitsprivatesecretkeywiththeAUTHENTICATIONSERVER -UserXdoesn’tknowtheprivatekeyofuserY. •KeyDistribution:WhenXwantstocommunicatewithY,theyneedtouseasecretkeybetweenthem -ASisresponsiblefordistributingthissessionkey(conversationkey)betweenX andY •EverybodyhastotrustAS

  6. WORKING OF KERBEROS •Torequestaservicefromaserver,theclientgoesthroughthreephasesofauthentication •Phase1 –TheclientrequestsaticketfromtheKerberos –Kerberosgrantsaticketandasessionkey –Theticketisusedforrequestingotherticketsforvariousservices –Ticketconveystheidentityoftheclienttotheserver–Thesessionkeyisusedforconversationbetweenthe clientandtheserver

  7. …..continue Phase2 –Theclientusestheticketofthefirstphasetorequestaticketfromtheticket grantingserver(TGS)foraspecificservice Phase3 –Theclientpresentsthekeytotheserverfortheservice

  8. APPLICATIONSOFKERBEROS •WindowsserversuseKerberosastheprimaryauthenticationprotocol. •Telnet/FTPusesKerberos. •Authenticationforwebservices. •Authenticatingemailclientandservers.

  9. ATTACKSONKERBEROS •KDCsecurity •Availability •Replayattacks •Password-guessingattacks

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