	US 12,081,655 B2
	Secret sigmoid function calculation system, secret logistic regression calculation system, secret sigmoid function calculation apparatus, secret logistic regression calculation apparatus, secret sigmoid function calculation method, secret logistic regression calculation method, and program
Ibuki Mishina, Musashino (JP); Dai Ikarashi, Musashino (JP); Koki Hamada, Musashino (JP); and Ryo Kikuchi, Musashino (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
Appl. No. 17/281,245
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
PCT Filed Sep. 25, 2019, PCT No. PCT/JP2019/037451 § 371(c)(1), (2) Date Mar. 30, 2021, PCT Pub. No. WO2020/071187, PCT Pub. Date Apr. 9, 2020.
Claims priority of application No. 2018-189296 (JP), filed on Oct. 4, 2018.
Prior Publication US 2022/0006614 A1, Jan. 6, 2022
Int. Cl. H04L 9/08 (2006.01); G06F 7/556 (2006.01)

CPC H04L 9/085 (2013.01) [G06F 7/556 (2013.01); H04L 2209/46 (2013.01)]

15 Claims

1. A secret sigmoid function calculation system in which t₀and t_iare assumed to be real numbers that satisfy t₀<t_iand g(x) is assumed to be a secure computable function, and the secret sigmoid function calculation system is configured with three or more secret sigmoid function calculation apparatuses and calculates, from a share [[x]] of an input value x, a share [[σ′(x)]] of a value of a sigmoid function for the input value x, wherein the share of the input value x is concealed by secret sharing among the three or more secret sigmoid function calculation apparatuses, the secret sigmoid function calculation system comprising: a first comparing circuitry configured to generate a first comparison result [[c]] by [[c]]=less than([[x]], t_i) from the share [[x]]; a second comparing circuitry configured to generate a second comparison result [[d]] by [[d]]=greater than([[x]], to) from the share [[x]]; a first logical comparing circuitry configured to generate a first logical computation result [[e]] by [[e]]=not([[c]]) from the first comparison result [[c]]; a second comparing circuitry configured to generate a second logical computation result [[k]] by [[k]]=and([[c]], [[d]]) or [[k]]=mul([[c]], [[d]]) from the first comparison result [[c]] and the second comparison result [[d]]; and a function value comparing circuitry configured to calculate the share [[σ′(x)]] by [[σ′(x)]]=mul([[k]], [[g(x)]])+[[e]] from the share [[x]], the first logical computation result [[e]], and the second logical computation result [[k]], wherein the function g(x) is g(x)=ax+b (where a and b are real numbers), and the values of a, b, t_o, and t_iare determined by the range of x for which the value of the sigmoid function is to be calculated, and the values of t₀and t_iare determined such that −5<t₀and t_i<5 where the value of the sigmoid function is approximately 0 when x is less than or equal to −5 and is approximately 1 when x is greater than or equal to 5.