Encryption system, function value calculation method, and program

A function value calculation method comprising:

• generating, by an encrypting apparatus, pseudo-random numbers for respective pieces of data that are different from one another, and encrypting the generated pseudo-random numbers together with the respective pieces of the data;
• generating, by a random number seed management apparatus, a random number seed for the encrypting apparatus to generate the pseudo-random numbers, and delivering the generated random number seed to the encrypting apparatus;
• regenerating, by a signature apparatus, the pseudo-random numbers used by the encrypting apparatus for encrypting the respective pieces of the data, and generating control information for certifying validity of the respective pieces of the data from the regenerated pseudo-random numbers;
• verifying, by a security execution apparatus, the control information based on the pseudo-random numbers obtained by decrypting ciphertexts of the respective pieces of the data, and calculating a function value of data obtained by decrypting the ciphertexts when verification of the control information is successful;
• and
• acquiring, by a decrypting apparatus, a function program for obtaining the function value of the data from outside, and an index pair associating an index of data input to the function program and an index of a user corresponding to data input to the function program, and transmitting the function program and an index pair to the signature apparatus,
• wherein the function value calculation method further comprises:
• generating, by the encrypting apparatus, the pseudo-random numbers for the respective pieces of the data by using the delivered random number seed;
• acquiring, by the signature apparatus, the random number seed for regenerating the pseudo-random numbers based on the index pair from the random number seed management apparatus, calculating a signature based on the function program and the random number seed, and transmitting the signature as the control information to the decrypting apparatus;
• transmitting, by the decrypting apparatus, the signature to the security execution apparatus;
• and
• verifying, by the security execution apparatus, the signature.

A non-transitory computer readable recording medium storing a program for causing one or more processors to execute:

• generating, by an encrypting apparatus, pseudo-random numbers for respective pieces of data that are different from one another, and encrypting the generated pseudo-random numbers together with the respective pieces of the data;
• generating, by a random number seed management apparatus, a random number seed for the encrypting apparatus to generate the pseudo-random numbers, and delivering the generated random number seed to the encrypting apparatus;
• regenerating, by a signature apparatus, the pseudo-random numbers used by the encrypting apparatus for encrypting the respective pieces of the data, and generating control information for certifying validity of the respective pieces of the data from the regenerated pseudo-random numbers;
• verifying, by a security execution apparatus, the control information based on the pseudo-random numbers obtained by decrypting ciphertexts of the respective pieces of the data, and calculating a function value of data obtained by decrypting the ciphertexts when verification of the control information is successful;
• and
• acquiring, by a decrypting apparatus, a function program for obtaining the function value of the data from outside, and an index pair associating an index of data input to the function program and an index of a user corresponding to data input to the function program, and transmitting the function program and an index pair to the signature apparatus,
• wherein the program is further for causing the one or more processors to execute:
• generating, by the encrypting apparatus, the pseudo-random numbers for the respective pieces of the data by using the delivered random number seed;
• acquiring, by the signature apparatus, the random number seed for regenerating the pseudo-random numbers based on the index pair from the random number seed management apparatus, calculating a signature based on the function program and the random number seed, and transmitting the signature as the control information to the decrypting apparatus;
• transmitting, by the decrypting apparatus, the signature to the security execution apparatus;
• and
• verifying, by the security execution apparatus, the signature.