X Through the Firewall, and Other Application Relays

Organizations often impose an administrative security policy when they connect to other organizations on a public network such as the Internet. Many applications have their own notions of security, or they simply rely on the security of the underlying protocols. Using the X Window System as a case study, we describe some techniques for building application-specific relays that allow the use of applications across organizational boundaries. In particular, we focus on analyzing administrative and application-specific security policies to construct solutions that satisfy the security requirements while providing the necessary functions of the applications.