Cryptography question:

8. Alice wants to send a message to Bob. But Eve can intercept and read the messages. Whereas, Mallory can modify or forge the messages. Moreover, once Bob sends a message to Alice, he can sometimes deny it. Therefore, what security measures should Alice take for the following:

To ensure message confidentiality.

To ensure non-repudiation.

To ensure message integrity.

How can the secret key be securely shared between Alice and Bob?