Eicon Networks S92 Manuel d'utilisateur télécharger pdf (Page 125)

YuChakTinMichael‘sGIACGCFWProjectAssignment

Page 125

PPTP iseasyandinexpensivetoimplement.”

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PPTPisconsideredasreasonablysecure.AccordingtoChapter14,Lesson2ofthe

MicrosoftPressMCSETrainingKitWindows2000NetworkInfrastructure

Administration,

“ForVPNconnections,Windows2000usesMPPEwiththePPTP,andIPSec

encryptionwiththeL2TP.…MPPEusestheRivest_Shamir_Adleman(RSA)Rivest's

Cipher4(RC4)streamcipherandisonlyusedwheneithertheEAPTransportLayer

Security(TLS)orMSCHAP(version1orversion2)authenticationmethodsareused.

MPPEcanuse40bit,56bit,or128bitencryptionkeys.…Bydefault,thehighestkey

strengthsupportedbythecallingrouterandansweringrouterisnegotiatedduringthe

connectionestablishmentprocess. Iftheansweringrouterrequiresahigherkey

strengththanissupportedbythecallingrouter,theconnectionattempt isrejected.”

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RegardingauthenticationandencryptionunderPPTP,refertothedescriptionsfrom

Microsoft:

“TheuserattemptingthePPTPconnectionisauthenticatedusingPPPbaseduser

authenticationprotocolssuchasEAP,MSCHAP,CHAP,SPAP,andPAP.ForPPTP

connections,EA PTLSusingsmartcardsorMSCHAPversion2ishighly

recommendedastheyprovidemutualauthenticationandarethemostsecuremethods

ofexchangingcredentials.…MPPEcanuse40bit,56bit,or128bitencryptionkeys.

The40bitkeyprovidesbackwardcompatibilitywi thnonWindows2000clients.By

default,thehighestkeystrengthsupportedbytheVPNclientandVPNse rveris

negotiatedduringtheconnection establishmentprocess.IftheVPNserverrequiresa

higherkeystrengththanissupportedbytheVPNclient, theconnectionattemptis

rejected.…MPPEforVPNconnectionschangestheencryptionkeyforeachpacket.

Thedecryptionofeachpacketisindependentofthepreviouspacket.MPPEincludes

asequencenumberintheMPPEheader.Ifpacketsarelostorarriveoutoforder,the

encryptionkeysarechangedrelativetothesequencenumber.”

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http://www.microsoft.com/ntserver/ProductInfo/faqs/PPTPfaq.asp

http://www.amazon.com/exec/obidos/ASIN/0735613885/qid=1018719524/sr=11/ref=sr_1_1/104955

75700347903

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http://www.microsoft.com/WINDOWS2000/techinfo/reskit/samplechapters/inbe/inbe_vpn_hueq.asp

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Eicon Networks S92 Manuel d'utilisateur Page 125