The MYSEA project has produced an innovative architecture and corrresponding engineering prototype consisting of trusted security services and integrated operating system mechanisms for the protection of distributed multi-domain computing environments from malicious code and other attacks. These security services and mechanisms extend and interoperate with existing workstations, applications and open source operating systems, providing new capabilities for composing secure distributed systems using commercial off-the-shelf (COTS) components. The MYSEA technical demonstration illustrates the MYSEA architecture, as well as the mechanisms for providing multi-domain information protection, trusted path extension and quality of security service.