@misc{cryptoeprint:2007:252,
author = {Roberto Araujo, Ricardo Felipe Custodio, and Jeroen van de Graaf},
title = {A Verifiable Voting Protocol based on Farnel},
howpublished = {Cryptology ePrint Archive, Report 2007/252},
year = {2007},
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.