Journal of Information and Computing Science, JIC, Vol1 2006 No2

Security downgrading policies control information flow and permit information release from a high security level to low security level. Many security downgrading policies are treated as declassification. This paper extend security policies to operations than declassification , the security downgrading policies support downgrading in practical software, each downgrading step is annotated with some operations when some conditions are satisfied. The security type system is formalized as relaxed noninterference.