SolStd31 - CHAPTER 31 Network Security Solutions to Odd-Numbered Review Questions and Exercises Review Questions 1 A nonce is a large random number

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1 CHAPTER 31 Network Security Solutions to Odd-Numbered Review Questions and Exercises Review Questions 1. A nonce is a large random number that is used only once to help distinguish a fresh authentication request from a repeated one. 3. Both the Needham-Schroeder and the Otway-Rees protocols use a KDC for user authentication. 5. The Kerberos TGS issues a ticket for the real server and provides the session key between the sender and the receiver. 7. A certification authority (CA) is a federal or state organization that binds a public key to an entity and issues a certificate. 9. A frequently-changed password is more secure than a fixed password but less secure than a one-time password. However, a one-time password needs more effort from the system and the user. The system needs to check if the password is fresh every time the user tries to use the password. The user needs to be careful not to use the pervious one. A more frequently changed password can be used as an alternative. One solution is that the system initializes the process of changing the password by sending the new password, through a secure channel, and challenging the user to be sure that the right user has received the new password. Exercises 11. a. The algorithm meets the first criteria ( one-wayness ). It is not possible to find the original numbers if the digest is given. For example, if we know the digest is 76, we cannot find the original ten numbers. They can be any set of 10 numbers. b.
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This note was uploaded on 09/16/2010 for the course SETAS ETEC301 taught by Professor Multiple during the Winter '09 term at Centennial College.

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SolStd31 - CHAPTER 31 Network Security Solutions to Odd-Numbered Review Questions and Exercises Review Questions 1 A nonce is a large random number

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