Privacy-preserving analysis device, privacy-preserving analysis system, privacy-preserving analysis method, and computer readable medium

A privacy-preserving analysis system comprising:

• a first processing circuitry to generate, for each integer i of i=1 n concerning an integer n of 1 or more, a ciphertext cti encrypted from a sum mi of an encryption token etki, being a vector ui, and information xi;
• a second processing circuitry to generate a decryption key dk, with using a decryption token dtk and a user secret key ski, the decryption token dtk including the vector ui for each integer i, the user secret key ski being set with information yi for each integer i, the decryption key dk including a sum z of inner product of the vector ui and the information yi for each integer i;
• and
• a third processing circuitry to decrypt the ciphertext cti for each integer i, the ciphertext cti being generated by the encryption device, using a decryption algorithm in a cryptography that calculates inner product of information being set in the ciphertext and information being set in the user secret key, wherein
• the third processing circuitry generates decryption data Di and subtracts the sum z included in the decryption key dk generated by the decryption key generation device, from a sum of the decryption data Di for each integer i, thereby calculating a sum of inner product of the information xi and the information y for each integer i, and
• the decryption token dtk corresponds to the encryption token etki for each integer i of i=1 . . . , n.

A privacy-preserving analysis method comprising:

• acquiring, for each integer i of i=1 . . . , n concerning an integer n of 1 or more, a ciphertext ct encrypted from a sum mi of an encryption token etki, being a vector ui, and information xi;
• acquiring a decryption key dk generated with using a decryption token dtk and a user secret key ski, the decryption token dtk including the vector for each integer i, the user secret key ski being set with information yi for each integer i, the decryption key dk including a sum z of inner product of the vector ui and the information yi for each integer i;
• decrypting the ciphertext cti for each integer i, using a decryption algorithm in a cryptography that calculates inner product of information being set in the ciphertext and information being set in the user secret key;
• and
• generating decryption data Di and subtracting the sum z included in the decryption key dk from a sum of the decryption data Di for each integer, thereby calculating a sum of inner product of the information xi and the information yi for each integer, wherein
• the decryption token dtk corresponds to the encryption token etki for each integer i of i=1 . . . , n.

A non-transitory computer readable medium storing a privacy-preserving analysis program which causes a computer to execute:

• a ciphertext acquisition process of acquiring, for each integer i of i=1 . . . , n concerning an integer n of 1 or more, a ciphertext cti encrypted from a sum mi of an encryption token etki, being a vector ui, and information xi;
• a decryption key acquisition process of acquiring a decryption key dk generated with using a decryption token dtk and a user secret key ski, the decryption token dtk including the vector ui for each integer i, the user secret key ski being set with information yi for each integer i, the decryption key dk including a sum z of inner product of the vector ui and the information yi for each integer i;
• and
• a decryption process of decrypting the ciphertext cti for each integer i, using a decryption algorithm in a cryptography that calculates inner product of information being set in the ciphertext and information being set in the user secret key, wherein
• the decryption process generates decryption data Di and subtracts the sum z included in the decryption key dk from a sum of the decryption data Di for each integer, thereby calculating a sum of inner product of the information xi and the information yi for each integer, and
• the decryption token dtk corresponds to the encryption token etki for each integer i of i=1 . . . , n.