Network security: Protocol reference model and the trusted computer system evaluation criteria

In 1983, the National Computer Security Center (NCSC) (formerly the DODCSC) published the Trusted Computer System Evaluation Criteria (TCSEC). The TCSEC was re-issued and slightly revised as a DoD standard in December 1985 [1]. During January 1986, the NCSC decided to begin work on a Trusted Network Guideline (TNG), which interprets the TCSEC and extends it as necessary for networks. The TNG is being written at the same time as this article; a draft should be available when this is published.