Patent ID: 11868510
Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Field: Digital communication (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 2:
3. A secure computation apparatus,
where m is an integer equal to or greater than 2; [e]:=[e0], [em−1] is a share obtained by secret sharing of a flag e:=e0, . . . , em−1 in which last elements of each group are true and other elements are false when a table formed of a key attribute and a value attribute is grouped based on a value of the key attribute; {{σ}} is a share obtained by secret sharing of a permutation a which moves elements such that the last elements of each group are sequentially arranged from beginning when the table is grouped based on the value of the key attribute; and g is a maximum number of such groups,
the secure computation apparatus comprising processing circuitry configured to, in cooperation with other secure computation apparatuses:
generate a share [x] that becomes a vector x:=x0, . . . , xm−1 when reconstructed, using the share [e], by setting [xi]:=[i+1] when [ei] is true and set [xi]:=[m] when [ei] is false for each integer i greater than or equal to 0 and smaller than or equal to m−1,
generate a share [σ(x)] that becomes a sorted vector σ(x) which is the vector x as sorted by the permutation a when reconstructed, using the share [x] and the share {{σ}};
generate a share [c] that becomes a vector c:=c0, . . . , cmin(g,m)−1 representing the number of records in each group when reconstructed, using the share [σ(x)], by setting [ci]:=[σ(x)i−σ(x)i−1] for each integer i greater than or equal to 1 and smaller than or equal to min(g,m)−1 and setting [c0]:=[σ(x)0]; and
output the share [c] of the number of records without revealing the share [e].