PPT Slide

User Org

KDC

User

User Org

AAA Server

Application

TGT

UOST, AST

UOST, AST, Skey, AAuth

UOST, UAuth

Secure Channel

Figure 1d - Intra-Realm Pull Sequence

Application Performs Authentication

User Org Performs Authentication and Authorization

KDC: Kerberos Key Distribution Center

TGT: Ticket Granting Ticket

UOST: User Org AAA Server Service Ticket

AST: Application Service Ticket

Skey: Session key associated with UOST

AAuth: Authenticator created by User and encrypted with AST session key

UAuth: Authenticator created by Application and encrypted with Skey

AM: Message authorizing User to Application / Can be bound to:

User name or ID, User IP address, secure channel session between User and Application (if created - would need to pass the session key or identifier to the AAA server)

Encrypted Secure Channel

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Notes:

Slide Notes and Questions:

Need to use kerberos proxy tickets in this situation. This allows multiple IP addr, such as the Application’s IP addr, to be specified as

valid presenters in the ticket.

Requires the Application to have a relationship with the KDC and User Org.

What set of information does the authorization message (AM) contain?

What exactly is implied by “secure channel”?

Are there any security issues?

6. The reason why a secure channel is needed between the Application and the User Org authorization server is because the AM message is

not protected. The secure channel could be removed if AM is sent as a certificate signed with some shared secret between the Application

and the User Org authorization server. An encrypted, secure channel is needed between the User and the Application because the SKey

cannot be sent in the clear.

7. AST => {Tcs}Ks

Tcs => Application, User, IP addr of User, ts, lifetime, Kcs

Ks => Application’s shared key with the KDC

AAuth => {Ac}Kcs

Ac => name of User, IP addr of User, ts (New Ac must be generated per service request)

Kcs => Session key for User and Application

UOST => {Tcs}Ks

Tcs => User Org AAA server, User, IP addr of User, IP addr of Application, ts, lifetime, Kcs

Ks => User Org AAA server’s shared key with the KDC

UAuth => {Ac}Kcs

Ac => name of User, IP addr of User or Application, ts (New Ac must be generated per service request)

Kcs => Session key for User and User Org AAA server

* The IP addr of the Application may be used because the authenticator is created by the Application.