**Patent number: ** 11081024

**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 ([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 determines integers h0 and h1 satisfying h0?h1. A pattern computation part computes [ai]=[a0]+i, [bi]=[b0]?i, [ci]=[c0]?i and [di]=[d0]+i for i=h0, . . . , h1, and obtains a set S={([ai], [bi], [ci], [di])}i of secure texts of combinations of frequencies (ai, bi, ci, di).

**Type: **
Grant

**Filed: **
June 30, 2017

**Date of Patent: **
August 3, 2021

**Assignees: **
NIPPON TELEGRAPH AND TELEPHONE CORPORATION, TOHOKU UNIVERSITY

**Inventors: **
Koki Hamada, Koji Chida, Satoshi Hasegawa, Masao Nagasaki, Kazuharu Misawa