@misc{cryptoeprint:1999:001,
author = {Ronald Cramer and Victor Shoup},
title = {Signature Schemes Based on the Strong RSA Assumption},
howpublished = {Cryptology ePrint Archive, Report 1999/001},
year = {1999},
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.