@misc{cryptoeprint:2011:034,
author = {Niek J. Bouman and Serge Fehr},
title = {Secure Authentication from a Weak Key, Without Leaking Information},
howpublished = {Cryptology ePrint Archive, Report 2011/034},
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.