At least any one of input keys KA0, KA1, KB′0, and KB′1 is set so that the input keys KA0, KA1, KB′0, and KB′1 which satisfy KA1−KA0=KB′1−KB′0=di are obtained, and an output key Kig(I(A), I(B)) corresponding to an output value gi(I(A), I(B)) is set by using the input keys KA0, KA1, KB′0, and KB′1, where input values of a gate that performs a logical operation are I(A), I(B)∈{0, 1}, an output value of the gate is gi(I(A), I(B))∈{0, 1}, an input key corresponding to the input value I(A) is KAI(A), and an input key corresponding to the input value I(B) is KB′I(B).