Seamless access to different systems of different vendors at different sites is an important prerequisite to effective and efficient use of distributed resources. Learning about new systems, new software, and new interfaces is a timeconsuming task for users who actually want to run their applications. UNICORE is a project to overcome these difficulties by providing a uniform interface for job preparation and control which gives seamless and secure access to supercomputer resources. It is an ambitiousproject delivering a production ready prototype within two years. The presentation will focus on the UNICORE architecture, especially the protocol and the underlying security mechanisms.