@misc{cryptoeprint:2008:272,
author = {Somitra Kumar Sanadhya and Palash Sarkar},
title = {A New Hash Family Obtained by Modifying the SHA-2 Family},
howpublished = {Cryptology ePrint Archive, Report 2008/272},
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.