Secure computation system, secure computation server apparatus, secure computation method, and secure computation program

A secure computation server apparatus out of at least three secure computation server apparatuses connected to each other via a network in order to refer to shares of an array element corresponding to an index in an array of shares for an input of shares representing the index, the secure computation server apparatus including:

• a discriminant share generation part that computes discriminant shares configured so that the index relating to the input corresponds to a specific value from the shares representing the index relating to the input and possible combinations of index shares of the array;
• a combination configuration part that configures a combination of shares of an element in the array and the discriminant shares for all possible combinations of indices of the array;
• a shuffle part that shuffles the combinations;
• a reconstruction part that reconstructs the discriminant shares in the shuffled combinations;
• and
• a selection part that selects shares of an element in the array in the combinations where the reconstructed value is the specific value.

A secure computation method comprising at least three secure computation server apparatuses connected to each other via a network and referring to shares of an array element corresponding to an index in an array of shares for an input of shares representing the index, wherein

• each of the secure computation server apparatuses performs:
• computing discriminant shares configured so that the index relating to the input corresponds to a specific value from the shares representing the index relating to the input and possible combinations of index shares of the array;
• configuring a combination of shares of an element in the array and the discriminant shares for all possible combinations of indices of the array;
• shuffling the combinations;
• reconstructing the discriminant shares in the shuffled combinations;
• and
• selecting shares of an element in the array in the combinations where the reconstructed value is the specific value.

A non-transient computer readable medium storing a secure computation program causing at least three secure computation server apparatuses connected to each other via a network to refer to shares of an array element corresponding to an index in an array of shares for an input of shares representing the index, the secure computation program including processes of:

• computing discriminant shares configured so that the index relating to the input corresponds to a specific value from the shares representing the index relating to the input and possible combinations of index shares of the array;
• configuring a combination of shares of an element in the array and the discriminant shares for all possible combinations of indices of the array;
• shuffling the combinations;
• reconstructing the discriminant shares in the shuffled combinations;
• and
• selecting shares of an element in the array in the combinations where the reconstructed value is the specific value.