What is Universal Circuit $U_{e}$ I was reading research Paper. In which writer talks about universal circuit. I want to know how is universal circuit $U_{e}$ different from simple circuit. What properties they have. Is they hide structure of simple circuit
A universal circuit is one that can compute any circuit. Specifically, it receives as input the description of another circuit and an input, and it outputs the computation of the given circuit on the given input. In cases where you want to hide the structure of the circuit being computed, a universal circuit can achieve this for you.