Security analysis of a token ring using Ulysses

The Ulysses security modeling environment and methodology is illustrated by using a secure token ring network as an example. It is shown that by using a flow analyzer and a library of preproved components, it is possible to decompose the functionality of a system and to determine which components have possible security flaws. The analysis also highlights the issue of tradeoffs between requirements on systems. It is often the case that in order to achieve a high degree of security for a system it is necessary to implement measures which decrease its performance. For this reason, it is important to be able to quickly determine the security flaws of a system at the level of design, as Ulysses does, so that the relative benefits and disadvantages of design decisions can be weighed before they are implemented