关键词: 无干扰, 信息流安全模型, IP安全, TA安全

Abstract: IP-secure is proposed for intransitive policies. But the definitions of IP-secure for intransitive policies in these works suffer from some subtle flaws, such as the orders of the actions, and an altered definition called TA-secure is proposed. This paper analyzes IP-secure and TA-secure and tries to find the difference between them. It finds the conditions to exchange the order of two actions in a sequence, where the results are equal after executing function ipurge. It also finds the conditions to exchange the order of two actions in a sequence, where the results are equal after executing function ta. Then, it compares the conditions to find the difference. The exact condition when function ta can purge the orders of the actions which shouldn’t be known by the security domain is found. Based on the difference, it gives the requirement to make a system satisfy TA-secure when it is IP-secure.

Key words: noninterference, information security model, IP-secure, TA-secure