US 11,888,977 B2
Share generating device, share converting device, secure computation system, share generation method, share conversion method, program, and recording medium
Dai Ikarashi, Musashino (JP); Ryo Kikuchi, Musashino (JP); and Koji Chida, Musashino (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Chiyoda-ku (JP)
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Chiyoda-ku (JP)
Filed on May 12, 2022, as Appl. No. 17/742,632.
Application 17/742,632 is a division of application No. 16/640,092, granted, now 11,374,743, previously published as PCT/JP2018/030439, filed on Aug. 16, 2018.
Claims priority of application No. 2017-159345 (JP), filed on Aug. 22, 2017.
Prior Publication US 2022/0278829 A1, Sep. 1, 2022
Int. Cl. H04L 9/08 (2006.01)
CPC H04L 9/085 (2013.01) [H04L 9/0819 (2013.01); H04L 9/0869 (2013.01)] 6 Claims
OG exemplary drawing
 
1. A share converting device for secure communication that is a share converting device Ai included in N share converting devices A0, . . . , AN−1, wherein
N is an integer greater than or equal to 2, m is an integer greater than or equal to 1, m(i) is an integer greater than or equal to 0, i=0, . . . , N−1 holds, u=0, . . . , N−1 holds, P is a function, and a range of the function P belongs to a set Fm whose members are sequences of m elements of field F, and
the share converting device includes processing circuitry configured to:
accept a share SSi containing N−1 seeds sd, where d∈{0, . . . , N−1} and d≠i, and a member yj∈Fm(i) belonging to a set Fm(j), the share SSj being a share of plaintext x in secret sharing received, over a network, from a share generating device,
possess an arbitrary value ti∈Fm(i) jointly with another share converting device Aj−1 mod N,
obtain a share [yi]u∈Fm(i) of each share converting device Au by secret-sharing the member yi in accordance with Shamir's secret sharing scheme on an assumption that the arbitrary value ti is a share [yj]j−1 mod N of the share converting device Ai−1 mod N and outputs the share [yi]u,
accept shares [yd]i,
obtain function values P(sd)∈Fm of the seeds sd,
convert a set SETi of the N−1 function values P(sd), where d∈{0, . . . , N−1} and d≠i, which is a share of a function value e=f(P(s0), . . . , P(sN−1))∈Fm with respect to function values P(s0), . . . , P(sN−1) of N seeds s0, . . . , sN−1, into a share [e]j of the function value e in accordance with Shamir's secret sharing scheme, and
obtain a share [x]i of x=g−1(y, e) in accordance with Shamir's secret sharing scheme by secure computation using a share [y]i and the share [e]j, where the share [y]i which is expressed by shares [y0]i, . . . , [yN−1]i is a share of a function value y=g(x, e)∈Fm with respect to plaintext x and the function value e,
wherein each share SSj is a share that is transmitted respectively to each of the plurality of share converting devices Aj, and each share converting device Aj converts each respective share SSj, whose total amount of communication data is smaller than that of shares in accordance with Shamir's secret sharing scheme, into a respective share [x]j in accordance with Shamir's secret sharing scheme.