Can any one explain why circuit privacy is needed on homomorphic encryption?
When we say circuit privacy, we actually mean that the distribution over the result of the computation is the same (statistically close) to the distribution over an encryption of the result. This is needed because typically the party computing the circuit has its own private input and we need to protect this. However, if you are using FHE to just offload computation to a cloud in a private manner, then you not need circuit privacy. Rather, circuit privacy is needed when multiple parties with private inputs collaborate to compute an output.