Consider the following authentication protocol. R is the challenge sent by Bob to Alice, and KAB is the secret Alice and Bob share. Which of the following are secure for a session key? When answering this question, for each option, think about the three aspects:

a$.$ Can Trudy impersonate Alice to Bob?

b$.$ Can this session key be securely used to encrypt messages exchanged between Alice and Bob?

c$.$ If this session key happened to be known by Trudy, can Trudy find KAB?

To get full credit, for the options that are not secure$,$ briefly explain why it is not secure$,$ you can explain by giving a case where an attacker can compromise the communication.

d$.$ KAB XOR R

e$.\{$ KAB $+$ R$\}$ KAB

f$.\{$R$\}$R$+$ KAB

g$.\{$ KAB $\}$ KAB

h$.\{$R$\}$ KAB

i$.\{$ KAB $\}$R

Please explain each of them cleary. I also think that only e and f is secured because even if Trudy doesn't know KAB, but KAB already exposed to public from authentication process. It is not secured to only use KAB for encryption like h and g$.$ For option d$,$ I think Trudy can reverse to know R because XOR is not complex method. Could you please clarify and answer the question for me clearly and in details because I am confused? I am also confused whether option i$,\{$KAB$\}$R$,$ is secured for session key or not?