@misc{cryptoeprint:2004:022,
author = {Steven M. Bellovin and William R. Cheswick},
title = {Privacy-Enhanced Searches Using Encrypted Bloom Filters},
howpublished = {Cryptology ePrint Archive, Report 2004/022},
year = {2004},
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.