First Advisor

Tom Schubert

Term of Graduation

Winter 1996

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Computer Science


Computer Science




Computer security, Computer networks -- Security measures, X Window System (Computer system)



Physical Description

1 online resource (v, 75 pages)


This thesis demonstrates that a secure X system can be designed and implemented to be independent of a particular security policy. The advantages and costs of a separation of security policy and enforcement are examined by developing a large scale application, the DX windowing system, on a DTOS platform. DTOS is a high assurance operating system that isolates policy decisions in a Security Server. A security conscious process, such as DX, eliminates policy considerations from the code. The process instead consults the Security Server and enforces the decisions that server derives from the policy. The DX architecture is described and its internal design examined. A discussion of X Windows security issues and an evaluation of the DX response is included. The performance of DX is analyzed and future work in the area of secure X systems is considered.


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