On lower bounds on second--order nonliearities of bent functions obtained by using Niho power functions

In this paper we find a lower bound of the second-order nonlinearities of Boolean bent functions of the form $f(x) = Tr_{1}^{n}(\alpha_{1}x^{d_{1}} + \alpha_{2}x^{d_{2}})$,where $d_1$ and $d_2$ are Niho exponents. A lower bound of the second-order nonlinearities of these Boolean functions can also be obtained by using a result proved by Li, Hu and Gao (eprint.iacr.org/2010 /009.pdf). It is demonstrated that for large values of $n$ the lower bound obtained in this paper are better than the lower bound obtained by Li, Hu and Gao