Suppose that Alice, Bob and Charlie want to compute some functions without revealing each input to the function one another. We can construct the protocols using garbled circuits by multiple communications among the three parties.
Assuming all the parties are semi-honest, which party do we need to let be online in the following setting?
The function $f$ is evaluated by taking the input values from Alice and Bob. After the communication between Alice and Bob, we get some result $a$ in Bob's hand (but Bob does not know exact value of $a$).
The function $g$ is evaluated by taking the input values from Bob and Charlie. Bob takes as input $a$ to $g$.
Cleary, during the evaluation of $f$, Alice and Bob must be online. Must Alice be online during the evaluation of $g$?