Privacy Protection for Transactions of Digital Goods

摘要

In this paper we study the problem of how to protect users' privacy in web transactions of digital goods. In particular, we introduce a system which allows a user to disclose his/her identity information (such as user account or credit card number) to a web site in exchange for a digital item, but prevents the web site from learning which specific item the user intends to obtain. The problem concerned here is orthogonal to the problem of anonymous transactions [RSG98, RR98] but commensurate with the general problem of PIR (private information retrieval) [CGK95, CG97]. Most of the existing results in PIR, however, are theoretical in nature and can not be applied in practice due to their large communication and computational overheads. In the present paper, we introduce two practical solutions that satisfy the above two requirements and analyze their security and performance.