Comment on Kushilevitz's One-server Private Information Retrieval Scheme

In the e-commerce environment, the protection of users' privacy from a server was not considered feasible until the private information retrieval (PIR) problem was stated and solved. A PIR scheme allows a user to retrieve a data item from an online database while hiding the identity of the item from a database server. In 1995, Chor et al. stated private information retrieval (PIR) problem and proposed k-server solutions which replicate the same database on the k servers. In 1997, Kushilevitz et al. proposed a PIR scheme based on the quadratic-residue assumption using only one server (one database - database replication is not needed). The scheme can simplifies multi-server management and reduce costs. In this paper, we point out that Kushilevitz's PIR scheme will let the user get much more information than he/she should get in one query of the database.