@misc{cryptoeprint:2003:009,
author = {Palash Sarkar},
title = {Domain Extenders for UOWHF: A Finite Binary Tree Algorithm},
howpublished = {Cryptology ePrint Archive, Report 2003/009},
year = {2003},
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.