	US 12,412,487 B2
	Secret calculation system, apparatus, method and program
Ryo Kikuchi, Musashino (JP); Dai Ikarashi, Musashino (JP); and Hiroki Sudo, Musashino (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
Appl. No. 18/574,762
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
PCT Filed Jul. 8, 2021, PCT No. PCT/JP2021/025769 § 371(c)(1), (2) Date Dec. 28, 2023, PCT Pub. No. WO2023/281693, PCT Pub. Date Jan. 12, 2023.
Prior Publication US 2025/0131855 A1, Apr. 24, 2025
Int. Cl. H04L 29/06 (2006.01); G06F 17/16 (2006.01); G09C 5/00 (2006.01)

CPC G09C 5/00 (2013.01) [G06F 17/16 (2013.01)]

6 Claims

1. A secure computation system comprising a plurality of secure computation devices

in which m is a number of records and is an integer of 1 or more, k^→ is a vector of a key k^→=(k₁, . . . , k_m), f^→ is a vector of a flag f^→=(f₁, . . . , f_m), [α] is a ciphertext of α with α set as any value or any vector, and a predetermined operation using α as a ciphertext is possible,

wherein the plurality of secure computation devices comprises processing circuitry configured to:

generate a ciphertext [f′^→] and a ciphertext [k′^→] of a vector f′^→ and a vector k′^→ obtained by sorting the vector f^→ and the vector k^→, respectively, with a vector obtained by concatenating negative of the vector f^→ and the vector k^→ set as a key, using a ciphertext [f^→] of the vector f^→ and a ciphertext [k^→] of the vector k^→;

generate a ciphertext [e′^→] of a vector e′^→ including e_i(i=1, . . . , m) as an element by generating a ciphertext [e′_m] of e′_msuch that e′_i=0 is satisfied when f′_i=1 and k′_i≠k′_i+1or f′_i=1 and f₁₊₁=0 are satisfied or otherwise e′_i=1 is satisfied, and e′_m=0 is satisfied when f′_m=1 is satisfied or otherwise e′_m=1 is satisfied, with i=1, . . . , m−1 set, using the ciphertext [f′^→] and the ciphertext [k′^→];

generate a ciphertext [m′] of m′ with a result obtained by subtracting a number of records having a flag of 0 from the m set as m′, using at least the m;

generate a ciphertext [x^→] of a vector x^→ including x_i(i=1, . . . , m) as an element by generating a ciphertext [x_i] of x_ihaving a value of i when an element e_i=0 is satisfied, the element e_ibeing an element of the vector e^→, and a value of m′ when an element e_i=1 is satisfied, the element e_ibeing an element of the vector e^→, with i=1, . . . , m set, using the ciphertext [e′^→];

obtain a ciphertext [x′^→], a ciphertext [k″^→], and a ciphertext [e″^→] of a vector x′^→, a vector k″^→, and a vector e″^→ obtained by sorting the vector x^→, the vector k′^→, and the vector e′^→, respectively, with the vector e′^→ set as a key, using the ciphertext [e′^→], the ciphertext [x^→], and the ciphertext [k′^→];

generate a ciphertext [c^→] of a vector c^→ including c_i(i=1, . . . , m) as an element by generating a ciphertext [c_i] of c_ithat is a value obtained by subtracting an element x′_i−1from an element x′_iof the vector x′^→ with a ciphertext [x′₁] of an element x′₁of the vector x′^→ set as a ciphertext [c₁] and with i=2, . . . , m set, using the ciphertext [x″^→]; and

calculate a ciphertext [e′″^→] of a vector e′″^→ including a value obtained by subtracting each element of the vector e″^→ from 1, using the ciphertext [e″^→].