Encrypted database system, client terminal, database server, data linking method and program

An encrypted database server comprising a search unit which receives an encrypted first table having data in a-th and b-th columns and an encrypted second table having data in c-th column from a client terminal, stores the encrypted first and second tables, performs linking between the encrypted first and second tables in terms of data having a value q in the a-th column using the b-th and c-th columns as keys, in response to a partial link command including a search key received from the client terminal, and outputs a result of the linking to the client terminal, wherein

• the search unit extracts data having a value q in the a-th column from each of the encrypted first and second tables, and performs linking together the extracted pieces of data using the b-th and c-th columns as keys by the use of the secret key.

A non-transitory computer readable storage medium recording thereon an encrypted data linking program for an encrypted database system including a client terminal and an encrypted database server, causing a computer in the client terminal to execute steps comprising:

• encrypting an inputted first table having data in a-th and b-th columns and an inputted second table having data in c-th column by the use of a secret key stored in advance and outputting the encrypted first and second tables to the encrypted database server;
• and
• sending a partial link command to perform linking between the encrypted first and second tables in terms of data having a value q in the a-th column using the b-th and c-th columns as keys, to the encrypted database server, along with a search key generated from the secret key.

A non-transitory computer readable storage medium recording thereon an encrypted data linking program for an encrypted database system including a client terminal and an encrypted database server, causing a computer in the encrypted database server to execute steps comprising:

• receiving an encrypted first table having data in a-th and b-th columns and an encrypted second table having data in c-th column from a client terminal, and storing the encrypted first and second tables;
• and
• in response to a partial link command including a search key received from the client terminal, extracting data having a value q in the a-th column from each of the encrypted first and second tables by the use of the secret key, performing linking together the extracted pieces of data using the b-th and c-th columns as keys, and sending back a result of the linking to the client terminal.