Registration apparatus, search operation apparatus, data management apparatus

A registration apparatus comprising:

• processing circuitry
• to generate a data random number tuple R that is a tuple of random numbers whose quantity is the same as a level quantity L of a hierarchy that a user attribute forms, and that is also a tuple of uniformly random numbers, and a tag random number tuple R′ that is a tuple of random numbers whose quantity is the same as the level quantity L, and that is also a tuple of uniformly random numbers,
• to accept a plaintext M and attribute information B that indicates an attribute value by level of a user who is allowed to refer to the plaintext M,
• to execute a function F_2 by taking as input a concatenated value of an attribute value of each level j in the attribute information B and a number of each level j, to execute a function F_3 by taking as input a function value of the function F_2, to calculate an attribute element C_{j, 0, 0} that is an exclusive-or of a function value of the function F_3 and a jth random number of the data random number tuple R, to execute a function F_4 by taking as input the plaintext M and an exclusive-or of the data random number tuple R, and to generate encrypted data C that includes the attribute element C_{j, 0, 0} and a ciphertext C_{L+1} which is a function value of the function F_4,
• to execute the function F_2 by taking as input a concatenated value of an attribute value of each level j in the attribute information B and a number of each level j, to execute a function F_5 by taking as input a function value of the function F_2 and a registered keyword, to execute a function F_6 by taking as input a function value of the function F_5, to calculate an attribute element CT_{j, 0, 0} that is an exclusive-or of a function value of the function F_6 and a jth random number of the tag random number tuple R′, to execute a function F_7 by taking as input an exclusive-or of the tag random number tuple R′, and to generate an encrypted tag CT_{W_n} that includes the attribute element CT{j, 0, 0} and a determination element CT_{L+1} which is a function value of the function F_7, and
• to register a tuple of the encrypted data C and the encrypted tag CT_{(W_n} in a data management apparatus.

A search operation apparatus comprising

• processing circuitry
• to calculate an attribute keyword element Q_j that is a value obtained by executing a function F_5 by taking as input a search keyword w, and to generate a search query Q that includes the attribute keyword element Q_j,
• to transmit the search query Q to a data management apparatus and to receive encrypted data C from the data management apparatus, and
• to perform decryption into a plaintext M by executing a decryption function of a function F_4 by taking as input a ciphertext C_{L+1} included in the encrypted data C,
• wherein the data management apparatus comprises:
• a storage unit in which a tuple of the encrypted data C and an encrypted tag CT_{W_n} is registered by a registration apparatus;
• an acceptance unit to receive the search query Q from the search operation apparatus;
• a collation unit to execute a function F_6 by taking as input the attribute keyword element Q_j included in the search query Q, to execute a function F_7 by taking as input a computation value V_1 which is based on a function value of the function F_6, and to compare a collation value V_2 that is a value obtained by executing the function F_7, with a determination element CT_{L+1} included in the encrypted tag CT_{W_n};
• and
• an output unit to transmit the encrypted data C to the search operation apparatus if the collation value V_2 matches the determination element CT_{L+1}, and
• wherein the registration apparatus comprises:
• a random number generation unit to generate a data random number tuple R and a tag random number tuple R′ that are each a tuple of random numbers whose quantity is the same as a level quantity L of a hierarchy that a user attribute forms, and that are also each a tuple of uniformly random numbers,
• an acceptance unit to accept the plaintext M and attribute information B that indicates an attribute value by level of a user who is allowed to refer to the plaintext M;
• an encrypted data generation unit to execute a function F_2 by taking as input a concatenated value of an attribute value of each level j in the attribute information B and a number of each level j, to execute a function F_3 by taking as input a function value of the function F_2, to calculate an attribute element C_{j, 0, 0} that is an exclusive-or of a function value of the function F_3 and a jth random number of the data random number tuple R, to execute the function F_4 by taking as input the plaintext M and an exclusive-or of the data random number tuple R, and to generate the encrypted data C that includes the attribute element C_{j, 0, 0} and the ciphertext C_{L+1} which is a function value of the function F_4;
• an encrypted tag generation unit to execute the function F_2 by taking as input a concatenated value of an attribute value of each level j in the attribute information B and a number of each level j, to execute the function F_5 by taking as input a function value of the function F_2 and a registered keyword, to execute the function F_6 by taking as input a function value of the function F_5, to calculate an attribute element CT_{j, 0, 0} that is an exclusive-or of a function value of the function F_6 and a jth random number of the tag random number tuple R′, to execute the function F_7 by taking as input an exclusive-or of the tag random number tuple R′, and to generate the encrypted tag CT_{W_n} that includes the attribute element CT_{j, 0, 0} and the determination element CT_{L+1} which is a function value of the function F_7;
• and
• a registration unit to register a tuple of the encrypted data C and the encrypted tag CT_{W_n} in the data management apparatus.

A data management apparatus comprising:

• processing circuitry, in which a tuple of encrypted data C and an encrypted tag CT_{W_n} is registered by a registration apparatus,
• to receive a search query Q from a search operation apparatus,
• to execute a function F_6 by taking as input an attribute keyword element Q_j included in the search query Q, to execute a function F_7 by taking as input a computation value V_1 which is based on a function value of the function F_6, and to compare a collation value V_2 that is a value obtained by executing the function F_7, with a determination element CT_{L+1} included in the encrypted tag CT_{W_n}, and
• to transmit the encrypted data C to the search operation apparatus if the collation value V_2 matches the determination element CT_{L+1},
• wherein the search operation apparatus comprises:
• a search query generation unit to calculate the attribute keyword element Q_j that is a value obtained by executing a function F_5 by taking as input a search keyword w and to generate the search query Q that includes the attribute keyword element Q_j;
• a request unit to transmit the search query Q to the data management apparatus and to receive the encrypted data C from the data management apparatus;
• and
• a decryption unit to perform decryption into a plaintext M by executing a decryption function of a function F_4 by taking as input a ciphertext C_{L+1} included in the encrypted data C, and
• wherein the registration apparatus comprises:
• a random number generation unit to generate a data random number tuple R and a tag random number tuple R′ that are each a tuple of random Iunbers whose quantity is the same as a level quantity L of a hierarchy that a user attribute forms, and that are also each a tuple of uniformly random numbers;
• an acceptance unit to accept the plaintext M and attribute information B that indicates an attribute value of by level of a user who is allowed to refer to the plaintext M;
• an encrypted data generation unit to execute a function F_2 by taking as input a concatenated value of an attribute value of each level j in the attribute information B and a number of each level j, to execute a function F_3 by taking as input a function value of the function F_2, to calculate an attribute element C_{j, 0, 0} that is an exclusive-or of a function value of the function F_3 and a jth random number of the data random number tuple R, to execute the function F_4 by taking as input the plaintext M and an exclusive-or of the data random number tuple R, and to generate the encrypted data C that includes the attribute element C_{j, 0, 0} and the ciphertext C_{L+1} which is a function value of the function F_4;
• an encrypted tag generation unit to execute the function F_2 by taking as input a concatenated value of an attribute value of each level j in the attribute information B and a number of each level j, to execute the function F_5 by taking as input a function value of the function F_2 and a registered keyword, to execute the function F_6 by taking as input a function value of the function F_5, to calculate an attribute element CT_{j, 0, 0} that is an exclusive-or of a function value of the function F_6 and a jth random number of the tag random number tuple R′, to execute the function F_7 by taking as input an exclusive-or of the tag random number tuple R′, and to generate the encrypted tag CT_{W_n} that includes the attribute element CT_{, 0, 0} and the determination element CT_{L+1} which is a function value of the function F_7;
• and
• a registration unit to register a tuple of the encrypted data C and the encrypted tag CT_{W_n} in the data management apparatus.