文摘
Turan gave bounds on the number of maximum-length feedback functions with nonlinearity 2 and t for even t<2 n−2 in the paper (Crypto. Commun. 4 (3-4), pp. 233-243 (2012)). In this correspondence, we give two further results. First, the exact number of maximum-length feedback functions with nonlinearity 2 is obtained. Second, an improved bound on the number of maximum-length feedback functions with nonlinearity t<2 n−2 is given.