@misc{cryptoeprint:2011:175,
author = {Marine Minier, Maria Naya-Plasencia, and Thomas Peyrin},
title = {Analysis of reduced-SHAvite-3-256 v2},
howpublished = {Cryptology ePrint Archive, Report 2011/175},
year = {2011},
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.