Alice will send a short message to Bob over an insecure channel. The message would be sent to Bob along with an encrypted message digest. Bob is required to authenticate and verify the integrity of the message sent.

Explain the mechanisms by which Bob can verify the integrity of the message and the authenticity of the sender.

Discuss how effective these mechanisms are in stopping an attacker from performing the following attacks: eavesdropping, modifying messages and impersonation. Use scenarios and diagrams to support your answer explaining how the attack would succeed or how the protocol will prevent it.