Please answer the below questions.

4.1 List ways in which secret keys can be distributed to two communicating parties.

4.2 What is the difference between a session key and a master key?

4.3 What is a key distribution center?

4.4 What entities constitute a full-service Kerberos environment?

4.5 In the context of Kerberos, what is a realm?

4.6 What are the principal differences between version 4 and version 5 of Kerberos?

4.7 What is nonce?

4.8 What are two different uses of public-key cryptography related to key distribution?

4.9 What are the essential ingredients of a public-key directory?

4.10 What is a public-key certificate?

4.11 What are the requirements for the use of a public-key certificate scheme?

4.12 What is the purpose of the X.509 standard?

4.13 What is a chain of certificates? 4.14 How is an X.509 certificate revoked?