@misc{cryptoeprint:2010:573,
author = {Yongqiang Li and Mingsheng Wang},
title = {On permutation polynomials EA-equivalent to the inverse function over $GF(2^n)$},
howpublished = {Cryptology ePrint Archive, Report 2010/573},
year = {2010},
note = {\url{http://eprint.iacr.org/}},
}
You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.