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Unformatted text preview: ge consisting of an index number, her name, Bob’s name, and a random number, all encrypted in the key she shares with Trent. She sends this message to Bob along with the index number, her name, and his name: I,A,B,EA(RA,I,A,B) (2) Bob generates a message consisting of a new random number, the index number, Alice’s name, and Bob’s name, all encrypted in the key he shares with Trent. He sends it to Trent, along with Alice’s encrypted message, the index number, her name, and his name: I,A,B,EA(RA,I,A,B),EB(RB,I,A,B) (3) Trent generates a random session key. Then he creates two messages. One is Alice’s random number and the session key, encrypted in the key he shares with Alice. The other is Bob’s random number and the session key, encrypted in the key he shares with Bob. He sends these two messages, along with the index number, to Bob: I,EA(RA,K),EB(RB,K) (4) Bob sends Alice the message encrypted in her key, along with the index number: I,EA(RA,K) (5) Alice decrypts the message to recover her key and random number. She then confirms that both have not changed in the protocol. Assuming that all the random numbers match, and the index number hasn’t changed along the way, Alice and Bob are now convinced of each other’s identity, and they have a secret key with which to communicate. Kerberos
Kerberos is a variant of NeedhamSchroeder and is discussed in detail in Section 24.5. In the basic Kerberos Version 5 protocol, Alice and Bob each share keys with Trent. Alice wants to generate a session key for a conversation with Bob. (1) Alice sends a message to Trent with her identity and Bob’s identity. A,B (2) Trent generates a message with a timestamp, a lifetime, L, a random session key, and Alice’s identity. He encrypts this in the key he shares with Bob. Then he takes the timestamp, the lifetime, the session key, and Bob’s identity, and encrypts these in the key he shares with Alice. He sends both encrypted messages to Alice. EA(T,L,K,B),EB(T,L,K,A) (3) Alice generates...
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 Fall '10
 ALIULGER
 Cryptography

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