Executing Query over Encrypted Character Strings in Databases

A query scheme which conducts fast LIKE query and range query over the encrypted character strings in databases is proposed in this paper. Firstly, a characteristics matrix is created for every character string in a sensitive attribute of a table to describe the characteristics of the character string. The characteristics matrix is also extended to describe the characteristics of a Chinese character string. Then the characteristics matrix is compressed to a bit string as the index of the character string and the bit string is stored into an index attribute of the sensitive attribute. Moreover, any LIKE query and range query over the sensitive attribute are converted into the queries over the index attribute. Suitable length m for the index attribute and the number of random functions k are selected after we balance the tradeoff between security and efficiency. Finally, we evaluate the efficiency and performance of queries over the encrypted character string. The experimental results indicate the performance for the queries in our scheme has been improved.