3.1 List three approaches to message authentication. 3.2 What is
3.1 List three approaches to message authentication. 3.2 What is a message authentication code? 3.4 What properties must a hash function have to be useful for message authentication? 3.5 In the context of a hash function, what is a compression function? 3.6 What are the principal ingredients of a public-key cryptosystem? 3.7 List and briefly define three uses of a public-key cryptosystem. 3.8 What is the difference between a private key and a secret key? 3.9 What is a digital signature?