Encrypted Keyword Search Mechanism Based on Bitmap Index for Personal Storage Services

The remote storage service has been one of the most popular cloud services. However, outsourcing in the remote storage causes a privacy issue such as the exposure of personal data and the leakage of private information. In this paper, we focus on the encrypted keyword search problem, called searchable symmetric encryption in cryptography, to reserve the user privacy and the data confidentiality in cloud storage services. Even though many works have been introduced, they still suffer from limitations in their practical use due to high search costs and huge index size. We present a new keyword search mechanism based on the bitmap index that represents a set of files in the inverted index form. The proposed mechanism has fast search time and small index size compared with the previous works in practical use. We show that it can be directly applied to practical services by testing the known NoSQL database, Couch base.