Middleware is a layer of software between the network and applications that provides services such as identification, authentication, authorization, directories, and security that are increasingly critical in the use of high-performance networks. In today's Internet, applications usually have to provide these services themselves, which leads to competing and incompatible standards and implementations. With direction provided by the Middleware Architecture Committee for Education (MACE), the Internet2 Middleware Initiative has focused on addressing the issue of inter-institutional authorization, with a strong emphasis on standardization and interoperability. A lead project in this effort is Shibboleth®, a powerful, scalable, and easy-to-use system for securely sharing online services or digital content. The Shibboleth system offers a privacy-protecting alternative to many authorization systems that rely on users' identities to grant access to online resources. As high-performance networks increasingly enable new capabilities for collaborating and accessing resources, technologies such as Shibboleth are vital to using them securely and efficiently.