@misc{cryptoeprint:2008:372,
author = {Shaojing Fu, Chao Li, Longjiang Qu, Ping Li},
title = {Enumeration of Balanced Symmetric Functions over GF(p)},
howpublished = {Cryptology ePrint Archive, Report 2008/372},
year = {2008},
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.