 In practice one might want to have more concrete functions bounding the adversary's success probability and to choose the security parameter large enough that this probability is smaller than some threshold, say 2−128.One of the reasons that negligible functions are used in foundations of complexity-theoretic cryptography is that they obey closure properties.Specifically,


Conversely, if formula_35 is not negligible, then neither is formula_39 for any real polynomial formula_36.