# Simulation-based proof in the semi-honest model when a party is corrupted

Would you mind telling me based on the attached file, why in case 3(corrupted client B), the authors did not use the real input which is $$S_B$$ and instead they have generated $$S'_B$$? In this case, I think the reason why authors have generated $$S'_A$$ is that party B has no access to $$S_A$$(belongs to party A), but why did they generate $$S'_B$$, considering that party B has access to $$S_B$$(the real input)? So, based on this security proof, the input $$S_B$$ has no role in the process of the simulation by the simulator!

It would be highly appreciated if you could help me with this.