@misc{cryptoeprint:2012:222,
author = {Kai-Yuen Cheong},
title = {A secret sharing scheme of prime numbers based on hardness of factorization},
howpublished = {Cryptology ePrint Archive, Report 2012/222},
year = {2012},
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.