Automatic proxy-based watermarking for WWW

摘要

With the appearance of digital libraries and information archive centers on the Internet, copyright issues are becoming very concerning. Unlike hardcopies, digital data can be modified and distributed very easily. Watermarking is the solution to this copyright problem. By embedding a secure, identifiable mark on the digital data, ownership and content integrity can be ensured. Currently, the watermarking process is usually done manually and off line. This makes updating of watermarking techniques and watermark logo content difficult. Enforcement of watermarking policies within an organization for providing content on the Internet is also not easy. Furthermore, installing watermarking software on each workstation of an organization is not very cost effective. In this paper, we propose a novel approach to address the copyright issues of digital data on the Internet. The basic idea is to move the watermarking process from the content developers to a reverse proxy server that is usually close to the organization's gateway. Data will be watermarked only when it is retrieved through this proxy. The main advantages of this approach are that : (i) it is cost effective as being independent of the amount of data on the web server and also independent of the number of content developers in the organization, (ii) it makes updates and maintenance tasks easy, being an one-for- all solution, and (iii) the reverse proxy effectively enforces the watermarking guideline. Both design considerations and implementation details of watermarking in a fully functional, Squid--based reverse proxy server are presented and its performance is analyzed. All results show that automatic watermarking in a reverse proxy server is a practical, cost efficient and enforcement effective solution for handling copyright issues in Internet digital libraries.