Causal security [computer systems]

This paper gives a new definition of security, which takes causal information into account. The new definition can be used to determine the security of nondeterministic concurrent systems for which high-level information may be either input into the system during its operation, or inherent in the original state of the system. It is possible to have systems which are secure under this definition which write to audit before performing each transition. The definition satisfies several useful composition properties, including one which gives it some protection from Trojan horse attacks