Secure computation system, secure computation device, secure computation method, and program

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+dN. A reference frequency computation part computes a secure text ([a], [b], [c], [d]) of a combination of reference frequencies (a, b, c, d) which are integers satisfying a+b=a+b, c+d=c+d, a+c=a+c, and b+d=b+d. A number-of-patterns determination part determines integers hand hsatisfying h≤h. A pattern computation part computes [ai]=[a]+i, [b]=[b]−i, [c]=[c]−i and [d]=[d]+i for i=h, . . . , h, and obtains a set S={([a], [b], [c], [d])}of secure texts of combinations of frequencies (a, b, c, d).