@misc{cryptoeprint:2006:223,
author = {Daniel R. L. Brown},
title = {What Hashes Make RSA-OAEP Secure?},
howpublished = {Cryptology ePrint Archive, Report 2006/223},
year = {2006},
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.