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Abstract

Fisher's exact test is efficiently computed through secure computation. It is assumed that a, b, c and d are frequencies of a 2×2 contingency table, [a], [b], [c] and [d] are secure texts of the respective frequencies a, b, c and d, and N is an upper bound satisfying a+b+c+d≤N. A reference frequency computation part 12 computes a secure text ([a₀], [b₀], [c₀], [d₀]) of a combination of reference frequencies (a₀, b₀, c₀, d₀) which are integers satisfying a₀+b₀=a+b, c₀+d₀=c+d, a₀+c₀=a+c, and b₀+d₀=b+d. A number-of-patterns determination part 13 determines integers h₀ and h₁ satisfying h₀≤h₁. A pattern computation part 14 computes [ai]=[a₀]+i, [b_i]=[b₀]−i, [c_i]=[c₀]−i and [d_i]=[d₀]+i for i=h₀, . . . , h₁, and obtains a set S={([a_i], [b_i], [c_i], [d_i])}_i of secure texts of combinations of frequencies (a_i, b_i, c_i, d_i).

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First Claim