3AAuthenticationAuthorization(Accounting

http://www.qksrv.net/interactive?nvc_cj=1&pid=1300521&aid=10292438&url=http://www.clipart.com/en/search/split&q=animated+devil

Eavesdropping

Masquerading

Message tampering

DOS

-Replaying

Infiltration

Traffic analysis

data, control messages

Alice Bob

Trudy

AliceTrudy

BobTrudy

data, control messages

Alice Bob

Trudy

data, control messages

Alice Bob

Trudy

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•HMACS

•MD5SHAMAC

•Identiy Based Access ControlRule Based Access Control(Security label)

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Authentication

Non-Repudiation

Authentication

Authorization

AccountingA Access control

Authentication

AuthorizationAccounting

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Message Digest5(MD5)

Secure Hash Standard

SHA-1

SHA-512

SHA-384

SHA-256

Message Authentication Codes(MACS)

Hash Function

Hash Code

H1H2H3H4H5..

Hj

P1P2P3P4P5.....pii=2n

n>>m

j=2m

MacHash

Mac

Pdf