Secret grouping apparatus, secret grouping system, secret grouping method, and program

A secret grouping system which classifies a plurality of elements into one or more groups through secret calculation, comprising:

• a memory;
• and
• a processor coupled to the memory and configured to
• receive, as an input, a target vector in which the plurality of elements are disposed so that elements belonging to a same group are continuous, a group information vector representing a last element in the group, and a classification destination vector representing a classification destination of each of the elements in the group;
• calculate a detection vector representing a last element of elements classified into a same classification destination in the group by using the target vector, the group information vector, and the classification destination vector;
• and
• stably sort the target vector and the detection vector with respect to the classification destination vector to create a target vector after classifying each of the elements into the classification destination in the group and a group information vector representing a last element in a group after the classification.

A secret grouping method performed by a computer in which a plurality of elements are classified into one or more groups through secret calculation, the secret grouping method comprising:

• receiving, as an input, a target vector in which the plurality of elements are disposed so that elements belonging to a same group are continuous, a group information vector representing a last element in the group, and a classification destination vector representing a classification destination of each of the elements in the group;
• calculating a detection vector representing a last element of elements classified into a same classification destination in the group by using the target vector, the group information vector, and the classification destination vector;
• and
• stably sorting the target vector and the detection vector with respect to the classification destination vector to create a target vector after classifying each of the elements into the classification destination in the group and a group information vector representing a last element in a group after the classification.