@misc{cryptoeprint:2010:507,
author = {Lilya Budaghyan and Tor Helleseth},
title = {On isotopisms of commutative presemifields and CCZ-equivalence of functions},
howpublished = {Cryptology ePrint Archive, Report 2010/507},
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.