@misc{cryptoeprint:2007:269,
author = {Jeroen van de Graaf},
title = {Voting with Unconditional Privacy by Merging Prêt-à-Voter and PunchScan},
howpublished = {Cryptology ePrint Archive, Report 2007/269},
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.