Homomorphic cyclic operation system, homomorphic cyclic operation apparatus, homomorphic cyclic operation method, and homomorphic cyclic operation program

A homomorphic cyclic operation apparatus performing a homomorphic cyclic operation on a periodic array of data using homomorphic encryption having a homomorphic operation defined with respect to at least one multiplication, wherein:

• a periodic array is formed by selecting rows corresponding to a periodic data from a score table indicating the similarity relationships between each element of the periodic data and connecting the rows into a single line, and
• the homomorphic cyclic operation apparatus shifts the periodic array in a ciphertext of periodic data by encrypting the periodic array of data by storing the periodic array in the coefficients of an indeterminate polynomial to generate the ciphertext and multiplying the indeterminate raised to the power of a shift amount to the ciphertext, and calculates similarity between the periodic data and a comparison periodic data by performing an inner product operation between the ciphertext of the periodic array and the ciphertext of the comparison array which assigns 1 to matching positions and 0 to non-matching positions based on elements contained in a comparison periodic data.

A non-transitory computer readable medium storing a program causing a computer to perform a homomorphic cyclic operation on a periodic array of data using homomorphic encryption having a homomorphic operation defined with respect to at least one multiplication, wherein:

• the periodic array is formed by selecting rows corresponding to the periodic data from a score table indicating the similarity relationships between each element of the periodic data and connecting the rows into a single line, and
• the program shifts the periodic array of data in a ciphertext of periodic data by multiplying the indeterminate raised to the power of a shift amount to the ciphertext, wherein the ciphertext of the periodic data is encrypted by storing the periodic array in the coefficients of an indeterminate polynomial, and calculates similarity between the periodic data and a comparison periodic data by performing an inner product operation between the ciphertext of the periodic array and the ciphertext of the comparison array which assigns 1 to matching positions and 0 to non-matching positions based on elements contained in a comparison periodic data.