@misc{cryptoeprint:2003:021,
author = {Edith Elkind and Helger Lipmaa},
title = {Interleaving Cryptography and Mechanism Design: The Case of Online Auctions},
howpublished = {Cryptology ePrint Archive, Report 2003/021},
year = {2003},
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.