I'm working with the above figure which shows a challenge-response protocol.
Kc - shared key between the host and the client B' - is a biometric captured by device BT' - biometric template computed from B' D' - device authenticator.
Match(BT', BT) returns yes if the user computed biometric matches with the template, no otherwise.
Verify(D', D) checks the validity of the authenticator. If all succeed at the host, host returns yes.
My question is, does message 3 from client > host need to be encrypted for integrity protection?
My instinct is no it doesn't, and using a keyed MAC is sufficient, because encryption does not guarantee integrity protection.