| 摘要 |
Conventionally, when a range retrieval is performed in an encrypted DB (database), because the size of a data value and a number of retrieval keys for the range retrieval are correlated, the content of the encrypted data can be assumed and safety is not sufficient. Further, insertion and retrieval of data is not sufficiently effective. Provided is an invention wherein a predetermined number of retrieval keys associated with data are generated without depending on the sizes of the data values. Further, when a retrieval key representing a range is generated, the widths of the ranges are prepared from a narrow range to a wide range, and the width has a relationship of power length, to thereby suppress the number of retrieval keys necessary at the time of data insertion and data retrieval. |
