In all kinds of information systems, the amount of the key is large, and the correlation of which is complex. To solve this problem, an evaluation method for the key security based on the measure of the static state characteristics is proposed. In this way, the security state of all kinds of keys in the information systems, can be measured well and truly, by the means of formalization modeling of the set of keys, the design of the security level and the probability of uncontrollability. As well as it, the category and the level of the key can also be considered well, and the security states of the key can be reflected reliably, so the security of the information system can be achieved.
