@misc{cryptoeprint:2005:040,
author = {Juan M. Estevez-Tapiador and Almudena Alcaide},
title = {Unfairness of a protocol for certified delivery},
howpublished = {Cryptology ePrint Archive, Report 2005/040},
year = {2005},
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.